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Report Title
“Integrated Geologic-Engineering Model for Reef and Carbonate Shoal Reservoirs Associated withPaleohighs: Upper Jurassic Smackover Formation, Northeastern Gulf of Mexico”
Type of Report
Technical Progress Report for Year 1
Reporting Period Start Date
September 1, 2000
Reporting Period End Date
August 31, 2001
Principal Author
Ernest A. Mancini (205/348-4319)Department of Geological SciencesBox 870338202 Bevill BuildingUniversity of AlabamaTuscaloosa, AL 35487-0338
Date Report was Issued
September 14, 2001
DOE Award Number
DE-FC26-00BC15303
Name and Address of Participants
Ernest A. ManciniDept. of Geological SciencesBox 870338Tuscaloosa, AL 35487-0338
Bruce S. HartEarth & Planetary SciencesMcGill University3450 University St.Montreal, Quebec H3A 2A7CANADA
Thomas BlasingameDept. of Petroleum EngineeringTexas A&M UniversityCollege Station, TX 77843-3116
Robert D. Schneeflock, Jr.Paramount Petroleum Co., Inc.230 Christopher CoveRidgeland, MS 39157
Richard K. StrahanStrago Petroleum Corporation811 Dallas St., Suite 1407Houston, TX 77002
Roger M. ChapmanLongleaf Energy Group, Inc.319 Belleville Ave.Brewton, AL 36427
Disclaimer
This report was prepared as an account of work sponsored by an agency of the United StatesGovernment. Neither the United States Government nor any agency thereof, nor any of theiremployees, makes any warranty, express or implied, or assumes any legal liability or responsibilityfor the accuracy, completeness, or usefulness of any information, apparatus, product, or process dis-closed, or represents that its use would not infringe privately owned rights. Reference herein to anyspecific commercial product, process, or service by trade name, trademark, manufacturer, or otherwisedoes not necessarily constitute or imply its endorsement, recommendation, or favoring by the UnitedStates Government or any agency thereof. The views and opinions of authors expressed herein do notnecessarily state or reflect those of the United States Government or any agency thereof.
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ABSTRACT
The University of Alabama in cooperation with Texas A&M University, McGill University,
Longleaf Energy Group, Strago Petroleum Corporation, and Paramount Petroleum Company are
undertaking an integrated, interdisciplinary geoscientific and engineering research project. The
project is designed to characterize and model reservoir architecture, pore systems and rock-fluid
interactions at the pore to field scale in Upper Jurassic Smackover reef and carbonate shoal
reservoirs associated with varying degrees of relief on pre-Mesozoic basement paleohighs in the
northeastern Gulf of Mexico. The project effort includes the prediction of fluid flow in carbonate
reservoirs through reservoir simulation modeling which utilizes geologic reservoir characterization
and modeling and the prediction of carbonate reservoir architecture, heterogeneity and quality
through seismic imaging.
The primary objective of the project is to increase the profitability, producibility and efficiency
of recovery of oil from existing and undiscovered Upper Jurassic fields characterized by reef and
carbonate shoals associated with pre-Mesozoic basement paleohighs.
The principal research effort for Year 1 of the project has been reservoir description and
characterization. This effort has included four tasks: 1) geoscientific reservoir characterization,
2) the study of rock-fluid interactions, 3) petrophysical and engineering characterization and 4) data
integration. This work was scheduled for completion in Year 1.
Overall, the project work is on schedule. Geoscientific reservoir characterization is essentially
completed. The architecture, porosity types and heterogeneity of the reef and shoal reservoirs at
Appleton and Vocation Fields have been characterized using geological and geophysical data. The
study of rock-fluid interactions has been initiated. Observations regarding the diagenetic processes
influencing pore system development and heterogeneity in these reef and shoal reservoirs have been
made. Petrophysical and engineering property characterization is progressing. Data on reservoir
production rate and pressure history at Appleton and Vocation Fields have been tabulated, and
porosity data from core analysis has been correlated with porosity as observed from well log
response. Data integration is on schedule, in that, the geological, geophysical, petrophysical and
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engineering data collected to date for Appleton and Vocation Fields have been compiled into a
fieldwide digital database for reservoir characterization, modeling and simulation for the reef and
carbonate shoal reservoirs for each of these fields.
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Table of Contents
Page
Title Page ............................................................................................................................ i
Disclaimer .......................................................................................................................... i
Abstract .............................................................................................................................. ii
Table of Contents ............................................................................................................... iv
Introduction ........................................................................................................................ 1
Executive Summary ........................................................................................................... 8
Experimental ...................................................................................................................... 10
Work Accomplished in Year 1 ..................................................................................... 12
Work Planned for Year 2 ..............................................................................................
Results and Discussion .......................................................................................................
Geoscientific Reservoir Characterization .....................................................................
Rock-Fluid Interactions ................................................................................................
Petrophysical and Engineering Property Characterization ...........................................
Data Integration ............................................................................................................
Conclusions ........................................................................................................................
References ..........................................................................................................................
INTRODUCTION
The University of Alabama in cooperation with Texas A&M University, McGill University,
Longleaf Energy Group, Strago Petroleum Corporation, and Paramount Petroleum Company is
undertaking an integrated, interdisciplinary geoscientific and engineering research project. The
project is designed to characterize and model reservoir architecture, pore systems and rock-fluid
interactions at the pore to field scale in Upper Jurassic Smackover reef and carbonate shoal
reservoirs associated with varying degrees of relief on pre-Mesozoic basement paleohighs in the
northeastern Gulf of Mexico. The project effort includes the prediction of fluid flow in carbonate
reservoirs through reservoir simulation modeling that utilizes geologic reservoir characterization and
modeling and the prediction of carbonate reservoir architecture, heterogeneity and quality through
seismic imaging.
The Upper Jurassic Smackover Formation (Figure 1) is one of the most productive
hydrocarbon reservoirs in the northeastern Gulf of Mexico. Production from Smackover carbonates
totals 1 billion barrels of oil and 4 trillion cubic feet of natural gas. The production is from three
plays: 1) basement ridge play, 2) regional peripheral fault play, and 3) salt anticline play (Figure 2).
Unfortunately, much of the oil in the Smackover fields in these plays remains unrecovered because
of a poor understanding of the rock and fluid characteristics that affects our understanding of
reservoir architecture, heterogeneity, quality, fluid flow and producibility. This scenario is
compounded because of inadequate techniques for reservoir detection and the characterization of
rock-fluid interactions, as well as imperfect models for fluid flow prediction. This poor
understanding is particularly illustrated for the case with Smackover fields in the basement ridge
play (Figure 3) where independent producers dominate the development and management of these
fields. These producers do not have the financial resources and/or staff expertise to substantially
improve the understanding of the geoscientific and engineering factors affecting the producibility of
Smackover carbonate reservoirs, which makes research and application of new technologies for
reef-shoal reservoirs all that more important and urgent. The research results from studying the
fields identified for this project will be of direct benefit to these producers.
H aynesville For mation
B uckner A nhydr ite M ember
Smackover For mation
Nor phlet For mation
" B asement"Paleozoic
Jura
ssic
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Mid
dle
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ssic
Up
per
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anO
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Figure 1. Jurassic stratigraphy in the study area.
Jack
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ASIN
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E PL
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ERIPH
ERAL
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oxim
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itof
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ileG
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Figur
e 2. M
ajor p
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udy a
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N
ALABAMAFLORIDA
Gulf of MexicoSCALE
0 10 20 Miles
LEGENDApproximate updip limitof Smackover
Basement arch, ridge, or anticline
Salt-related fault-block ondownthrown side
Figure 3. Location of Appleton and Vocation / South Vocation Fields.
AppletonField
Vocationand SouthVocation Fields
WigginsArch Baldwin
High
MobileGraben
ManilaEmbayment
ConecuhEmbayment
Pollard Fault System
FosheeFaultSystem
Conecuh Ridge
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ge
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plex
Gilbertown Fault System
West Bend
Fault System
MississippiInterior SaltBasin
Pensacola-Decatur
Ridge Complex
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This interdisciplinary project is a 3-year effort to characterize, model and simulate fluid flow in
carbonate reservoirs and consists of 3 phases and 11 tasks. Phase 1 (1 year) of the project involves
geoscientific reservoir characterization, rock-fluid interactions, petrophysical and engineering
property characterization, and data integration. Phase 2 (1.5 years) includes geologic modeling and
reservoir simulation. Phase 3 (0.5 year) involves building the geologic-engineering model, testing
the geologic-engineering model, and applying the geologic-engineering model.
The principal goal of this project is to assist independent producers in increasing oil
producibility from reef and shoal reservoirs associated with pre-Mesozoic paleotopographic
features through an interdisciplinary geoscientific and engineering characterization and modeling of
carbonate reservoir architecture, heterogeneity, quality and fluid flow from the pore to field scale.
The objectives of the project are as follows:
1. Evaluate the geological, geophysical, petrophysical and engineering properties of reef-shoal
reservoirs and their associated fluids, in particular, the Appleton (Figure 4) and Vocation Fields
(Figure 5).
2. Construct a digital database of integrated geoscience and engineering data taken from reef-
shoal carbonate reservoirs associated with basement paleohighs.
3. Develop a geologic-engineering model(s) for improving reservoir detection, reservoir
characterization, flow-space imaging, flow simulation, and performance prediction for reef-
shoal carbonate reservoirs based on a systematic study of Appleton and Vocation Fields.
4. Validate and apply the geologic-engineering model(s) on a prospective Smackover reservoir
through an iterative interdisciplinary approach, where adjustments of properties and concepts
will be made to improve the model(s).
This project has direct and significant economic benefits because the Smackover is a prolific
hydrocarbon reservoir in the northeastern Gulf of Mexico. Smackover reefs represent an
underdeveloped reservoir, and the basement ridge play in which these reefs are associated
represents an underexplored play, Initial estimations indicate the original oil resource target
2
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Figure 4. Appleton Field Unit area.
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8
available in this play from the 40 fields that have been discovered and developed approximates at
least 160 million barrels. Any newly discovered fields are expected to have an average of 4 million
barrels of oil. The combined estimated reserves of the Smackover fields (Appleton and Vocation
Fields) proposed for study in this project total 9 million barrels of oil. Successful completion of the
project should lead to increased oil producibility from Appleton and Vocation Fields and from
Smackover reservoirs in general. Production of these domestic resources will serve to reduce U.S.
dependence on foreign oil supplies.
Completion of the project will contribute significantly to the understanding of: the geologic
factors controlling reef and shoal development on paleohighs, carbonate reservoir architecture and
heterogeneity at the pore to field scale, generalized rock-fluid interactions and alterations in
carbonate reservoirs, the geological and geophysical attributes important to geologic modeling of
reef-shoal carbonate reservoirs, the critical factors affecting fluid flow in carbonate reservoirs,
particularly with regard to reservoir simulation and the analysis of well performance, the elements
important to the development of a carbonate geologic-engineering model, and the geological,
geophysical, and/or petrophysical properties important to improved carbonate reservoir detection,
characterization, imaging and flow prediction.
EXECUTIVE SUMMARY
The University of Alabama in cooperation with Texas A&M University, McGill University,
Longleaf Energy Group, Strago Petroleum Corporation, and Paramount Petroleum Company are
undertaking an integrated, interdisciplinary geoscientific and engineering research project. The
project is designed to characterize and model reservoir architecture, pore systems and rock-fluid
interactions at the pore to field scale in Upper Jurassic Smackover reef and carbonate shoal
reservoirs associated with varying degrees of relief on pre-Mesozoic basement paleohighs in the
northeastern Gulf of Mexico. The project effort includes the prediction of fluid flow in carbonate
reservoirs through reservoir simulation modeling which utilizes geologic reservoir characterization
and modeling and the prediction of carbonate reservoir architecture, heterogeneity and quality
through seismic imaging.
9
The primary objective of the project is to increase the profitability, producibility and efficiency
of recovery of oil from existing and undiscovered Upper Jurassic fields characterized by reef and
carbonate shoals associated with pre-Mesozoic basement paleohighs.
The principal research effort for Year 1 of the project has been reservoir description and
characterization. This effort has included four tasks: 1) geoscientific reservoir characterization,
2) the study of rock-fluid interactions, 3) petrophysical and engineering characterization and 4) data
integration. This work was scheduled for completion in Year 1.
Geoscientific reservoir characterization is essentially completed. The architecture, porosity
types and heterogeneity of the reef and shoal reservoirs at Appleton and Vocation Fields have been
characterized using geological and geophysical data. All available whole cores (11) from Appleton
Field have been described and thin sections (379) from these cores have been studied. Depositional
facies were determined from the core descriptions. The thin sections studied represent the
depositional facies identified. The core data and well log signatures have been integrated and
calibrated on graphic logs. For Appleton Field, the well log, core, and seismic data have been
entered into a digital database and structural maps on top of the basement, reef, and
Smackover/Buckner have been constructed. An isopach map of the Smackover interval has been
prepared, and thickness maps of the sabkha facies, tidal flat facies, shoal complex, tidal flat/shoal
complex, and reef complex have been prepared. Maps have been constructed using the 3-D seismic
data that Longleaf contributed to the project to illustrate the structural configuration of the basement
surface, the reef surface, and Buckner/Smackover surface. Petrographic analysis and pore system
studies have been initiated and will continue into Year 2 of the project.
All available whole cores (11) from Vocation Field have been described and thin sections (237)
from the cores have been studied. Depositional facies were determined from the core descriptions.
From this work, an additional 73 thin sections are being prepared to provide accurate representation
of the lithofacies identified. The core data and well log signatures have been integrated and
calibrated on the graphic logs. The well log and core data from Vocation Field have been entered
into a digital database and structural and isopach maps are being constructed using these data. The
10
graphic logs are being used in preparing cross sections across Vocation Field. The core and well
log data are being integrated with the 3-D seismic data that Strago contributed to the project.
Petrographic analysis and pore system studies have been initiated and will continue into Year 2 of
the project.
The study of rock-fluid interactions has been initiated. Thin sections (379) are being studied
from 11 cores from Appleton Field to determine the impact of cementation, compaction,
dolomitization, dissolution and neomorphism has had on the reef and shoal reservoirs in this field.
Thin sections (237) are being studied from 11 cores from Vocation Field to determine the
paragenetic sequence for the reservoir lithologies in this field. An additional 73 thin sections are
being prepared from the shoal and reef lithofacies in Vocation Field to identify the diagenetic
processes that played a significant role in the development of the pore systems in the reservoirs at
Vocation Field.
Petrophysical and engineering property characterization is progressing. Petrophysical and
engineering property data are being gathered and tabulated. The production history for Appleton
Field and the production history for Vocation and South Vocation Fields have been obtained and
graphed. Water and oil saturation data for core analyses for Appleton Field have been tabulated.
Porosity versus permeability cross plots for wells in the fields have been prepared, and porosities
from core analyses have been calibrated with porosities determined from well log studies.
Data integration is on schedule, in that, geological, geophysical and engineering data collected
to date for Appleton and Vocation Fields have been compiled into a fieldwide digital database for
reservoir characterization, modeling and simulation for the reef and carbonate shoal reservoirs for
each of these fields.
EXPERIMENTAL
The principal research effort for Year 1 of the project is reservoir description and
characterization. This effort includes four tasks: 1) geoscientific reservoir characterization, 2) the
study of rock-fluid interactions, 3) petrophysical and engineering characterization, and 4) data
integration (Table 1).
Table 1. Milestone Chart.
Project Year/QuarterTasks 2 0 0 0 2 0 0 1 2 0 0 2 2 0 0 3
3 4 1 2 3 4 1 2 3 4 1 2
Reservoir Characterization (Phase 1)Task 1—Geoscientific Reservoir Characterization xxxxxx xxxTask 2—Rock-Fluid Interactions xxxxxx xxxTask 3—Petrophysical Engineering Characterization xxxxxx xxxTask 4—Data Integration xxx
3-D Modeling (Phase 2)Task 5 xxxxxx
Task 6—3-D Reser xxxxxxTask 7—Geolo xxxxxx
Testing and Applying Model (Phase 3)Task 8—Testing Geologic-Engineering Model xxxxxx
Task 9—Applying Geolo xxxxxx
Technological TransferTask 10—Workshops xx xx
Technical ReportsTask 11—Quarterly, Topical and Annual Reports x x x x x x x x x x x
12
Work Accomplished in Year 1
Reservoir Description and Characterization (Phase 1)
Task 1—Geoscientific Reservoir Characterization.--This task will characterize reservoir
architecture, pore systems and heterogeneity based on geological and geophysical properties. This
work will be done for all well logs, cores, seismic data and other data for Vocation Field and will be
done for Appleton Field by integrating the new data obtained from drilling the sidetrack well in
Appleton Field and the data available from five additional cores and 3-D seismic in the field area.
The first phase of the task includes core descriptions, including lithologies, sedimentary structures,
lithofacies, depositional environments, systems tracts, and depositional sequences. Graphic logs
constructed from the core studies will depict the information described above. Core samples will be
selected for petrographic, XRD, SEM, and microprobe analyses. The graphic logs will be compared
to available core analysis and well log data. The core features and core analyses will be calibrated to
the well log patterns. A numerical code system will be established so that these data can be entered
into the digital database for comparison with the core analysis data and well log measurements and
used in the reservoir modeling. The next phase is the link between core and well log analysis and
reservoir modeling. It involves the preparation of stratigraphic and structural cross sections to
illustrate structural growth, lithofacies and reservoir geometry, and depositional systems tract
distribution. Maps will be prepared to illustrate lithofacies distribution, stratigraphic and reservoir
interval thickness (isolith and isopach maps), and stratal structural configurations. These cross
sections and maps, in association with the core descriptions, will be utilized to make sequence
stratigraphic, environment of deposition, and structural interpretations. Standard industry software,
such as StratWorks and Z-Map, will be used in the preparation of the cross sections and subsurface
maps. The third phase will encompass the interpreting of seismic data and performing stratigraphic
and structural analyses. Seismic interpretations will be guided by the generation of synthetic
seismograms resulting from the tying of well log and seismic data and by the comparison of
seismic transects with geologic cross sections. Seismic forward modeling and attribute-based
13
characterization will be performed. Structure and isopach maps constructed from well logs will be
refined utilizing the seismic data. The seismic imaging of the structure and stratigraphy, forward
modeling and attribute characterization will be accomplished utilizing standard industry software,
such as 2d/3d PAK, Earthwave and SeisWorks. The next phase includes identification and
quantification of carbonate mineralogy and textures (grain, matrix and cement types), pore topology
and geometry, and percent of porosity and is performed to support and enhance the visual core
descriptions. These petrographic, XRD, SEM and microprobe analyses will confirm and quantify
the observations made in the core descriptions. This analysis provides the opportunity to study
reservoir architecture and heterogeneity at the microscopic scale. The fifth phase involves study of
pore systems in the reservoir, including pore types and throats through SEM analysis. This phase
will examine pore shape and geometry and the nature and distribution of pore throats to determine
the features of the pore systems that are affecting reservoir producibility.
Appleton Field. All available whole cores (11) from Appleton Field have been described and
thin sections (379) from these cores have been studied. Graphic logs were constructed describing
each of the cores (Figures 6 through 16). Depositional facies were determined from the core
descriptions. The thin sections represent the depositional facies identified. The core data and well
log signatures have been integrated and calibrated on these graphic logs.
For Appleton Field (Figure 4), the well log and core data have been entered into a digital
database and structural maps on top of the basement (Figure 17), reef (Figure 18), and
Smackover/Buckner (Figure 19) have been constructed. An isopach map of the Smackover interval
has been prepared (Figure 20), and thickness maps of the sabkha facies (Figure 21), tidal flat facies
(Figure 22), shoal complex (Figure 23), tidal flat/shoal complex (Figure 24) and reef complex
(Figure 25) facies have been constructed. A cross section (Figure 26) illustrating the thickness and
facies changes across Appleton Field has been prepared.
The core and well log data have been integrated with the 3-D seismic data for Appleton Field
that Longleaf contributed to the project. A typical seismic profile for the field illustrating the reef
reservoir is shown in Figure 27. A structural configuration of the basement surface, the reef
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9.
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1.
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. Pan
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2.
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y B.
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Figu
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3.
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4.
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Figure 27. Seismic Profile.
Smackover/BucknerReef/Norphlet
Basement
36
surface, and Buckner/Smackover surface are illustrated in Figures 28 through 30. Cross sections
(Figures 31 and 32) illustrating the reservoir facies based on well data and on seismic data have
been prepared.
Petrographic analysis and pore system studies have been initiated and will continue into Year 2
of the project. Tables 2 and 3 provide a tabulation of the initial work in these two areas of research.
Vocation Field. All available whole cores (11) from Vocation Field have been described and
thin sections (237) from the cores have been studied. Graphic logs were constructed describing
each of the cores (Figures 33 through 43). Depositional facies were determined from the core
descriptions. From this work, an additional 73 thin sections are being prepared to provide accurate
representation of the lithofacies identified. The core data and well log signatures have been
integrated and calibrated on the graphic logs.
The well log and core data from Vocation Field have been entered into a digital database and
structural and isopach maps are being constructed using these data. Graphic logs have been
constructed for each of the cores. The core data and well log signatures are integrated and calibrated
on these graphic logs. The graphic logs are being used in preparing cross sections across Vocation
Field.
The core and well log data are being integrated with the 3-D seismic data that Strago
contributed to the project.
Petrographic analysis and pore system studies have been initiated and will continue into Year 2
of the project. Table 4 provides a tabulation of the initial work in these areas of research.
Task 2—Rock-Fluid Interactions.--This task is a continuation of the study of reservoir
architecture and heterogeneity at the microscopic scale. While macroscopic and mesoscopic
heterogeneities are largely a result of structural and depositional processes, microscopic
heterogeneities are often a product of diagenetic modification of the pore system. Macroscopic and
mesoscopic heterogeneities influence producibility by compartmentalizing the reservoir and
providing barriers to large-scale fluid flow. Microscopic heterogeneities, on the other hand,
influence producibility by controlling the overall rate of fluid flow through the reservoir. This task
Appl
eton
Fie
ld A
rea
Figu
re 2
8. B
asem
ent S
urfa
ce
(
from
sei
smic
dat
a).
By
B. J
. Pan
etta
.
N
Reef
NFigure 29. Reef Surface (from seismic data). By B. J. Panetta.
N
Figure 29. Reef Surface (from seismic data). By B. J. Panetta.
Reef
Figure 30. Buckner/Smackover surface (from seismic data). By B. J. Panetta.
Figu
re 3
1. C
ross
sec
tion
of re
serv
oir
facie
s (fr
om w
ell lo
gs).
By
B. J
. Pan
etta
.
5138
3854
6247
B48
35B
3986
4633
B49
91
Figu
re 3
2. C
ross
sec
tion
of re
serv
oir f
acie
s (fr
om s
eism
ic da
ta).
By
B. J
. Pan
etta
.
Poro
sity
.45 -.15
T able 2. Characteristics of Smackover Lithofacies in the Appleton Field Area.
Lithofacies Lithology Allochems Pore Types Porosity Permeability
Carbonate mudstone Dolostone andanhydritic dolostone
None Intercrystalline Low(1.2 to 2.5%)
Low(� 0.01 md)
Peloidal wackestone Dolostone tocalcareous dolostone
Peloids, ooids,intraclasts
Intercrystalline,moldic
Low to moderate(2.6 to 12.4%)
Low(� 0.01 to 0.11 md)
Peloidal packstone Dolomitic limestone Peloids, ooids,oncoids,intraclasts
Interparticulate,moldic,intercrystalline
Low to moderate(1.1 to 12.4%)
Low to moderate(� 0.01 to 0.51 md)
Peloidal/oncoidalpackstone
Dolostone tocalcareous dolostone
Peloids, oncoids,intraclasts
Interparticulate Low(1.2 to 6.1%)
Low(� 0.01 md)
Peloidal/ooliticpackstone
Dolostone Peloids, ooids,skeletal grains,intraclasts
Moldic,intercrystalline,interparticulate
Low(1.3 to 4.5%)
Low(� 0.01 md)
Peloidal grainstone Calcareous dolostone Peloids, oncoids,algal grains,intraclasts
Interparticulate,fenestral, moldic,interparticulate,vuggy
Low to high(1.0 to 19.9%)
Low to high(� 0.01 to 722 md)
Oncoidal grainstone Calcareous dolostoneto dolostone
Oncoids, peloids,intraclasts
Interparticulate,intraparticulate,fenestral
Low to moderate(1.4 to 11.9%)
Low to high(� 0.01 to 8.27 md)
Oolitic grainstone Dolostone tolimestone
Ooids, peloids,oncoids,intraclasts
Interparticulate,moldic,intercrystalline
Moderate to high(8.3 to 20.7%)
Moderate to high(3.09 to 406 md)
Oncoidal/peloidal/oolitic grainstone
Dolostone tocalcareous dolostone
Oncoids, peloids,ooids, algalgrains
Interparticulate,moldic, vuggy
Low to high(1.9 to 19%)
Low to high(� 0.01 to 219 md)
Algal grainstone Dolomitic limestone tocalcareous dolostone
Algal grains,oncoids,peloids, ooids
Interparticulate,moldic, vuggy,fenestral,intercrystalline
Low to high(1.7 to 23.1%)
Low to high(� 0.01 to 63 md)
Microbialboundstone(bafflestone)
Dolostone Algae, intraclasts,oncoids, peloids
Shelter, vuggy,interparticulate,intercrystalline
High(11.0 to 29.0%)
High(8.13 to 4106 md)
Microbial bindstone Dolostone Algae, peloids,ooids
Shelter, vuggy,fenestral, moldic,interparticulate
High(11.9 to 20.7%)
High(11 to 1545 md)
Algal laminite Dolostone todolomitic limestone
Algae, peloids,oncoids,intraclasts
Interparticulate,intercrystalline
Low(1.1 to 7.0%)
Low(� 0.01 md)
Anhydrite Anhydrite None None Low(� 1.0%)
Low(� 0.01 md)
Table 3. Smackover Genetic Depositional Systems at Appleton Field.
Genetic DepositionalSystem Depositional Environment Lithofacies
Sabkha Sabkha AnhydriteTidal flat Tidal flat Algal laminite, carbonate mudstoneShoal Shoal crest, shoal flank, lagoon Algal grainstone, oncoidal/peloidal/oolitic grainstone, oolitic grainstone,
oncoidal grainstone, peloidal grainstone, peloidal/oolitic packstone,peloidal/oncoidal packstone, peloidal packstone, peloidal wackestone
Reef Reef crest, reef flank, subtidal Microbial boundstone (bafflestone), microbial bindstone, carbonatemudstone
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
MD ms ws ps gs bs T S
13950'
13960'
13970'
13980'
13990'
14000'
14010'
S tructures & G rain T ype C yclesP oros ity
anhydrite
anhydrite
anhydrite
anhydrite
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
13950'
13960'
13970'
13980'
13990'
14000'
14010'
MD
iP Irregular distribution of poros ity due to patchy cementation
Level rich in sulphur (13974-13975')
C arbonaceous elongated clasts , up to 0.5cm
V ugs are completely cemented
V /iP /F rA Moderate poros ity, partially cementedS ome very thin fractures
V /iP
Microbial buildup, T ype IV and V . Oncolites up to 0.5cm in diameter are leached. T he voids are lined by a white crust
M/V /F r
G ood poros ity. F ractures filled with calcite/anhydrite
Oncolite level surrounded by anhydrite veins
Mudstone fragments embedded in anhydrite
B oundstone package with high poros ityT ype IV / V facies interbedded with T ype IAbundant elongated vertical (fractures? ) and horizontal (vugs) poresP yrite as cement
M/V /F e
F r?
anhydrite
Highly fractured mudstone. F ractures filled with anhydrite
x F r
x
x F r
x M/iP
x
x
Well P ermit No. 11185S T R AG O-B Y R D 26-13 #2
Figure 33. Graphic log for well Permit # 11185. By J. C. Llinas.
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
8
2
4
6
8
2
4
6
8
2
4
6
8
MD ms ws ps gs bs T S
13980'
13990'
14000'
14010'
14020'
14030'
14040'
14050'
14060'
14070'
14080'
14090'
S tructures & G rain T ype
C yclesP oros ity
no core
no core
no core
6
no core
x
x
x
x
x
x
x
M/V /iC
V /iP
M/V /iP
Highly cemented interval
F ractures filled with anhydrite
Microbial facies T ype II.T he vuggy poros ity decreases upwards
M/V
M/V Interval with very high poros ity (13996-14003')
F r
F r
T here is a white rim around the vugs that reduces their s ize
breccia
breccia
Microbial buildup T ype IV
V /iP Low poros ity
F ractures filled with anhydrite
F ractures filled with calcite
Microbial reef T ype I fabric. M/VF r S ome fractures and vugs filled with calcite
S tromatolite and thrombolite fabric. C avities filled with anhydrite. No poros ity
F ractures filled with calcite
S mall fractures filled with An/C aNo noticeable poros ityS ome floating clasts of the same material
No noticeable poros ity
A B ig anhydrite nodulesMicrobial buildup,T ype IM/V
Interbedding of some thin levels with thrombolite fabric No poros ity due to high cementation
R eef facies with thrombolite fabric, T ype I; sucros ic matrixModerate to good poros ity
F ractures filled with anhydrite
M/V
T ype IV microbial facies
Oil impregnated
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
8
2
4
6
8
2
4
6
8
2
4
6
8
MD
13980'
13990'
14000'
14010'
14020'
14030'
14040'
14050'
14060'
14070'
14080'
14090'
All pores and fractures are cemented by calcite
x
x V Microbial reef, T ype I facies
x
x
Well P ermit No. 1599 B .C . QUIMB Y 27-15 #1
Figure 34. Graphic log for well Permit # 1599. By J. C. Llinas.
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
MD ms ws ps gs bs T S
14100'
14130'
14140'
14150'
14160'
14170'
14180'
14190'
A
S tructures & G rain T ype C yclesP oros ity
no core
breccia
x
x
x
x
x
M/V /iP
M/V
R eef facies with thrombolite fabric, T ype IModerate to good poros ityM/V
High poros ity interval (14131-14142')
M/VV ery high to moderate poros ity
M/V
Anhydrite filling some fractures and voids . G ood poros ity
brecciaA
Anhydrite filling cavities and fractures
R eef facies with T ype I fabricS ucros ic matrix
Microbial facies T ype II
M/V
F r
Large elongated clasts of reef fabric in a sandy matrix
V ery low poros ityiP
Microbial facies T ype II
S ome patches with low poros ity, but good poros ity in general
Moderate to low poros ity due to high cementationiP
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
14130'
14140'
14150'
14160'
14170'
14180'
14190'
2
4
6
8
V /iP High poros ity
V /iP
Abundant elongated vugs (fractures? )
B ioturbation?
x
x
x Microbial facies T ype IIF rV
x S ucros ic texture?
x F r
Well P ermit No. 1599 (cont.) B .C . QUIMB Y 27-15 #1
?
14100'
Figure 34 (continued). Graphic log for well Permit # 1599. By J. C. Llinas.
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
8
2
4
6
8
2
4
6
8
2
4
6
8
MD ms ws ps gs bs T S
14130'
14140'
14150'
14160'
14170'
14180'
14190'
14200'
14270'
14280'
14290'
14300'
A
S tructures & G rain T ype C yclesP oros ity
HAY NE S V ILLEF OR MAT ION
anhydrite
no core
anhydrite
no core
x
x
x
x
x
x
xxx
x
x
x
x
xx
x
x
x
x
x
xx
x
x
6
A
A
T hin layers of nodular and layered anhydrite
A
V ery low poros ity
A
A
i C arbonaceous intraclasts?
V ery low poros ity
V ery low poros ity
M/iP /VA
A
A
V ery low poros ityM/iP
A
Microbial texture?M/iPModerate poros ity
A
M/iP Moderate to good poros ity
Oil?
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
6
8
2
4
6
8
2
4
6
8
14130'
14140'
14150'
14160'
14170'
14180'
14190'
14200'
14280'
14290'
14300'
MD
C arbonaceous particles
Layered and coalesced nodular anhydrite
P yrite concentrated in the stylolites
A V ery small carbonaceous particles?
Anhydrite filling bigger poresModerate to good poros ity
A
F e
No poros ity
A
V ery low poros ityP atchy texture
Low to moderate poros ity
F ex
xV ery low poros ity
x
x S ubtle plane parallel lamination
?
Well P ermit No. 1691C ONT AINE R C OR P . OF AME R IC A 34-5 #1
Figure 35. Graphic log for well Permit # 1691. By J. C. Llinas.
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
MD ms ws ps gs bs T S
14310'
14320'
14330'
S tructures & G rain T ype
C yclesP oros ity
14340'
x
x
xx
M/iP Moderate poros ity
mM/iP High poros ity
A
mM/iP High poros ity
mM/iP
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
14310'
14320'
14330'
MD
14340'
F r
P atchy texture
Open fractures
x
x
Well P ermit No. 1691(cont.)C ONT AINE R C OR P . OF AME R IC A 34-5 #1
Figure 35 (continued). Graphic log for well Permit # 1691B. By J. C. Llinas.
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
MD ms ws ps gs bs T S
14030'
14040'
14050'
14060'
14070'
14080'
14090'
A
S tructures & G rain T ype C yclesP oros ity
A
i
M/iP /V
iP /V
A
A
F r F ractures partially occluded by anhydrite/calcite cementS tylolites with pyrite
Intraclasts horizontally aligned
Anhydrite chicken wires
A
A
F ractures filled with calcite/anhydrite
Microbial buildup T ype I and T ype IV -V M/V /iP
S ome isolated elongated pores . Low poros ity
iP /V
M/iP /V
M/iP
M/iP
P ervas ive anhydrite cement occludes poros ity
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
MD
14030'
14040'
14050'
14060'
14070'
14080'
14090'
A
i
Moderate poros ity
iP
M/V
F r
V
P oros ity almost completely obliterated by calcite cement
High poros ity in the grainstones , moderate in the packstonesF r
M/iP /V
M/iP /V
High poros ity
Moderate to low poros ity
T hick carbonaceous laminae and anhydrite nodules iP /V /M
V ery porous level
F r
F rP atchy areas with good poros ity
A
Microbial facies , T ype IV and V
High interparticle and moldic poros ity but sometimes cemented by anhydrite, S ome thin intervals < 7 cm have the oncolites leachedincreas ing the vuggy poros ity
High poros ity despite partial cementation specially along thefractures
B ivalve debris
F ractures cemented by calcite/anhydrite
x
x
xx
x
x
x
x A
x
x
x
x
x
x
x
x
Well P ermit No. 2851M.J . B Y R D E T UX 26-13 #1
Figure 36. Graphic log for well Permit # 2851. By J. C. Llinas.
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
MD ms ws ps gs bs T S
14030'
14040'
14050'
14060'
14070'
14080'
14090'
14100'
14110'
14120'
14130'
14140'
A
S tructures & G rain T ype C yclesP oros ity
x
x
x
x
x
x
x
x
xx
x
x
xx
x
x
x
A
M/V /iP
iP
iP
iP
V ery low poros ity
V ery low poros ity
V ery low poros ity
B ig anhydrite nodulesF ractures also filled with anhydriteF r
V ery high poros ity
V ery high poros ityA
Anhidrite filling fractures
V /iP
F r
M/iP
M/V /iP
R eef, T ype II facies
M/V /iP
F r
F r
iP
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
MD
14030'
14040'
14050'
14060'
14070'
14080'
14090'
14100'
14110'
14120'
14130'
14140'
no core
F r
F rM/iP
V ery high poros ity
Moderate to good poros ity
Low to moderate poros ity
F r F ractures filled with anhydrite
Moderate to good poros ity
x V ery low poros ity
x
x
x
P atchy texture
Well P ermit No. 2935D.R . C OLE Y , J R . E S T AT E #35-4
Figure 37. Graphic log for well Permit # 2935. By J. C. Llinas.
2
4
6
8
2
4
6
8
MD ms ws ps gs bs T S
14150'
14160'
S tructures & G rain T ype C yclesP oros ity
V ery high poros ity
A
Anhidrite filling fractures
V /iP
F rV /iP
R eef, T ype II facies
A2
4
6
8
2
4
6
8
14150'
14160'
F r
MD
Well P ermit No. 2935 (cont.)D.R . C OLE Y , J R . E S T AT E #35-4
Figure 37 (continued). Graphic log for well Permit # 2935. By J. C. Llinas.
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
MD ms ws ps gs bs T S
14110'
14120'
14130'
14140'
14150'
14160'
14170'
14180'
14190'
14200'
14210'
14220'
A
S tructures & G rain T ype C yclesP oros ity
HAY NE S V ILLEF OR MAT ION
x
x
x
x
x
x
x
x
x
x
x
x
x
x
A
A
V ery low poros ityAnhydrite in layers and coalesced nodules
A V ery low poros ity
iPC arbonaceous intraclasts
M
M
A M/V Improvement in poros ity, though bigger pores are filled withanhydrite cement
M/V C arbonaceous intraclasts
M
M/V All the big pores are filled with anhydrite while the small ones are not.
M/V /iP C arbonaceous intraclasts
AV ery high poros ity. B ig anhydrite nodules M/V /iP
High poros ity
S mall vugs filled with anhydrite M/V /iP
A
A
A
M/iP
M/iP
M/iP
G ood poros ity
Moderate to low poros ity
P atches with high poros ity
M/V /iP
A M/V /iP
Low to moderate poros ity
M/V /iP High poros ity, vugs up to 1 cm in diameter
MIcrobial buildup (T ype II). May vugs filled with anhydrite
M/V /iP
B ig vugs upto 2cm in diameter and sometimes elongated. S omeare filled partially or totally by anhydrite
M/V /iP
A
S ome elongated vugs (fractures) up to 3 cm long. P atches of very high
Moderate poros ity
A
Microbial buildup T ype II
Leached intraclasts
F oss il remains like spicules replaced by calcite?
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
MD
14110'
14120'
14130'
14140'
14150'
14160'
14170'
14180'
14190'
14200'
14210'
14220'
Interval with patchy texture (14176-14211'), microbial influx?
F r
F r
M
F r
A
A
A
Low poros ity
C oncentration of pyrite in the stylolites
Low poros ity
E longated pores < 1cm
P atchy texture
poros ity
Highy fractured interval (14200-14205')
Low to moderate poros ity
x
x
x
x
x
x
A
x
i
i
i
i
i
i
i
Well P ermit No. 2966B .C . QUIMB Y 27-16 #1
Figure 38. Graphic log for well Permit # 2966. By J. C. Llinas.
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
MD ms ws ps gs bs T S
14230'
14240'
14250'
14260''
14270'
14280'
14290'
S tructures & G rain T ype C yclesP oros ity
x
x
x
M/V /iPi
Leached intraclasts
F oss il debris resembling spicules replaced by calcite
M/iP
M/iP
V ery low poros ity
V ery low poros ity
Oncolites disposed in thin levels
M/iP
M/V /iP
M/V /iP
M/V /iP
Low poros ity
Moderate to high poros ityS ome vugs are filled with anhydrite/calcite
or i
AM/iP
V ery low poros ity
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
MD
14230'
14240'
14250'
14260'
14270'
14280'
14290'
or
or
A
A
Interval with patchy texture (14268-14273'). Microbial influence?V
Interval with patchy texture and high vuggy poros ity (14256-14268'). Microbial influence?
V
V
S picules
Moderate to good poros ity
or
x
x
x
x
x
Well P ermit No. 2966 (cont.)B .C . QUIMB Y 27-16 #1
Figure 38 (continued). Graphic log for well Permit # 2966. By J. C. Llinas.
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
MD ms ws ps gs bs T S
14000
14010
14020
14030
14040
14050
14060
14070
14080
14090
14100
A
S tructures & G rain T ype C yclesP oros ity
xx
x
x
xxx
x
x
x
x
x
x
xx
xx
x
x
x
x
x
x
x
M/V /iP
Layered and nodular anhydrite interbedded with the mudstone
HAY NE S V ILLEF OR MAT ION
A
A
Layered and nodular anhydriteA
A
A
F e High fenestral poros ity completely filled with anhydrite as well as somefracturesS tromatolites and oncolites
A F r
Ip
A
A
A
V ery low poros ity level
Highly porous grainstones
M/V /iP
Low to moderate poros ity
V ery high poros ity
Oncolites>1cmM/V /iP
M/V /iP
P oros ity obliterated by An/C a
M/V /iP P oros ity obliterated by anhydrite/calcite
A
T ype IV /V microbial facies
F e M/V /iP
F enestral poros ity obliterated by An/C aModerate poros ity
AF r V ery low poros ity
M/V /iPF r P ores occluded by anhydrite
A M/V
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
MD
14000
14010
14020
14030
14040
14050
14060
14070
14080
14090
No poros ity
S tromatolites and oncolites
No poros ity
iP /V
Moderate to high poros ity
B ivalve fragments
A
A
Abundant clayey laminae
V ery low poros ity
B ig anhydrite nodules , aprox. 5cm diam
Moderate to low poros ity
Oncolites up to 3mm in diam. and stromatolites
V ery low poros ityS tylolites with pyiriteV ery thin mudstone levels interbedded
x G ood poros ity
x
x
x
x
x
Well P ermit No. 3412B .C . QUIMB Y 27-15 #2
Figure 39. Graphic log for well Permit # 3412. By J. C. Llinas.
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
MD ms ws ps gs bs T S
14020'
14030'
14040'
14050'
14060'
14070'
14080'
14090'
14100'
14110'
A
S tructures & G rain T ype C yclesP oros ity
xx
x
x
x
x
x
x
xx
x
x
x
xx
x
xx
x
x
x
xx
x
x
x
x
x
x
xx
x
x
Anhydrite cement
No poros ity
T he microbial buildup is mainlyT ype I and in minor degree T ype IV and V . High poros ity, though in thin intervals it is completely occluded by calcite cement
V
A
A
Intervals with vuggy/moldic poros ity, sometimes occluded with anhydrite or calcite cementS ome thin wackestone layers interbedded.
Interval with very low poros ity (14062-14068)
14015-14025: interval with very low poros ity
M/V
Microbial buildup T ype IV and V
M/V
M/V
M/V
M/V
E nhancement in poros ity due to ooids/peloids dissolution M/V /Ip
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
MD
14020'
14030'
14040'
14050'
14060'
14070'
14080'
14090'
14100'
14110'
no core
no core
i
i
i
i
i
A
M/V
M/V
iP
F r
iP
iP
iP
F r
F r
P oros ity almost completely cemented
F ractures partially infilled with anhidrite/calcite cement
E longated muddy intraclasts<1cm long
P ores partially obliterated by calcite cement
P yrite
F e
High poros ity interval (14069-14073)
Moderate to good poros ity from 14026 to 14042
x
x
Well P ermit No. 3739B E R T HA C . QUIMB Y 34-1 #1
Figure 40. Graphic log for well Permit # 3739. By J. C. Llinas.
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
MD ms ws ps gs bs T S
14270'
14280'
14290'
14300'
14310'
14320'
A
S tructures & G rain T ype C yclesP oros ity
i
M/iP
V ery low poros ity
i C arbonaceous intraclasts
i C arbonaceous intraclasts
10-15cm thick layers
V ery low poros ity
Alternation of 40-60cm thick ws/ps beds and 8-15cms ps/gs layers
A
A
V ery low poros ity
M/iP
M/iP
Low poros ity
Wackestone rich in carbonaceous material
G lauconite
Note: T he core is coated by drilling mud, therefore the descriptions are not very reliable. T hin sections must be done to confirm and improve them.
Alternation of 40-60cm thick ws/ps beds and 8-15cms ps/gs layers
M/iP
M/iP
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
MD
14270'
14280'
14290'
14300'
14310'
14320'
Discontinuous lamination
F r T hin fractures cemented by anhydrite
Interval with moderate to good poros ity (14288-14300')
No vis ible poros ity
A
A
F e F enestral poros ity filled with cement
x
x
x
x
x
x
F r T hin fractures cemented by anhydriteModerate to good poros ity
Well P ermit No. 3990D.R . C OLE Y , III UNIT 26-2 #1
Figure 41. Graphic log for well Permit # 3990. By J. C. Llinas.
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
MD ms ws ps gs bs T S
13940'
13950'
13960'
13970'
13980'
13990'
14000'
14010'
14020'
14030'
A
S tructures & G rain T ype C yclesP oros ity
Conglomera
tic
sandstone w
eathere
d
from
basem
ent
B asement
x
x
x
x
x
x
x
xx
x
x
x
x
x
x
x
xx
x
iP
M/iP
iP
iP
iP
iP
iP
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
13940'
13950'
13960'
13970'
13980'
13990'
14000'
14010'
14020'
14030'
MD
A
A
A
A
F r
F rA
A F r
A
A
Abundant anhydrite nodules
C ross s tratification
V ery high poros ity
V ery high poros ity
V ery thin more cemented layers within the grainstone
G rainstone with leached ooids
B ig anhydrite nodules
Moderate to good poros ity
F ractures cemented by anhydrite
F ractures cemented by anhydrite
Interbedding of layers of wackestone and very thin darker layers of mudstone
Lithoclasts
B ig anhydrite nodules
Wavy discontinuous lamination
Abundant lithoclasts
Angular to subangular feldspar grains up to 4cms, with an averageof 1cm. B ad sorting
No poros ity
No poros ity
V ery low poros ity
P resence of very thin beds of black matrix (carbonaceous? ) with lithoclasts floating in it.
x
x
x
x
x
A
Well P ermit No. 5779NE US C HWANDE R 34-3 #1
Figure 42. Graphic log for well Permit # 5779. By J. C. Llinas.
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
MD ms ws ps gs bs T S
13980'
13990'
14000'
14010'
14020'
14030'
A
S tructures & G rain T ype C yclesP oros ity
V /iP
A
V /iP
S ome thin (3-4cm) intervals with M/mV
S ome pores filled in with anhydrite
High poros ity due to oolite dissolution M/V /iP
AHighly fractured interval. Anhydrite cements the joints partially
Moderate poros ity. F ractures are partially filled with anhydrite V /iP /F r
Oncoid cortices . G ood poros ity due to allochems dissolution Abundant calcite/anhydrite veins
M/V
T hin microbial buildup layers interbedded with the wackestonesLow poros ity. S ome vuggy (fenestral? ) poros ity occludded by anhydrite
Microbial buildup, T ype I mainly. V ertical burrowsM/V
F ractured interval, diagenetic breccia. Nodular/layered anhidrite
Abundant elongated vugs
Anhydrite nodules .High vuggy poros ity. White crust lining the vugs .V ertical burrows and fracturesOncolite levels interbeded with wackestone layers with abundant s tylolites
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
2
4
6
8
MD
13980'
13990'
14000'
14010'
14020'
14030'
F r
V ery low poros ity
A
iP /V
P yrite disseminatedcalcite cement.
F r
F r
xA
x
x Moderate to good poros ity
x
x
xx
x
x
Well P ermit No. 7588BB LAC K S HE R 27-11 #1
Figure 43. Graphic log for well Permit # 7588B. By J. C. Llinas.
Table 4. Characterization of Smackover Lithofacies in the Vocation Field Area.
Lithofacies Lithology Allochems Pore Types Porosity(percent)
Permeability(md)
ooid-dominated,grain-supported
(grainstone/packstone)
dolostone,limestone
ooids, oncoids,peloids
moldic,interparticulate,intercrystalline
high(1.5-28.3)
high(0-2,230)
ooid-dominated,matrix-supported
(wackestone)
dolostone ooids, oncoids,peloids
moldic moderate(1.2-14.0)
moderate(0-8)
oncoid-dominatedgrain-supported
(grainstone/packestone)
dolostone oncoids,peloids, ooids,
intraclasts
interparticulate,moldic, vuggy
high(1.6-20.1)
high(0-1,635)
oncoid-dominatedmatrix-supported
(wackestone)
dolostone oncoids,peloids
vuggy, moldic low(2.5-8.3)
low(0-0.39)
peloid-dominatedgrain-supported
(grainstone/packestone)
dolostone,limestone
peloids,oncoids, ooids
interparticulate,intercrystalline,
vuggy
high(0.8-25.6)
high(0-587)
peloid-dominatedmatrix-supported
(wackestone)
dolostone,anhydriticdolostone
peloids,oncoids
intercrystalline moderate(1.0-18.2)
moderate(0-39)
mudstone dolostone,limestone
none fracture low(1.2 to 8.8)
low(<0.01)
algal stromatolite(boundstone)
dolostone algae, peloids,oncoids
fracture, vuggy,fenestral
low(1.1-8.8)
moderate(0-16)
algal boundstone dolostone algae, peloids,oncoids
vuggy, fracture,breccia, moldic
high(3.0-33.6)
high(0-2,998)
will involve an expansion of previous general studies of diagenesis within the Smackover and will
identify those diagenetic processes that have influenced reef and shoal carbonates in paleohigh
reservoirs using Appleton and Vocation Fields as models. This work will document the impact of
cementation, compaction, dolomitization, dissolution and neomorphism on reef and shoal reservoirs.
A detailed paragenetic sequence will be constructed for reservoir lithologies in each field to
document the diagenetic history of these lithologies and to determine the timing of each individual
diagenetic event. Attention will be focused on spatial variation in diagenesis within each field and
also in variations in diagenesis between fields. The influence of paleohigh relief on diagenesis will
be identified. This work will incorporate petrographic, XRD, SEM, and microprobe analyses to
characterize, on a microscopic scale, the nature of the pore system in the Appleton and Vocation
reservoirs. This task will focus on the evolution of the pore systems through time and on the
identification of those diagenetic processes that played a significant role in the development of the
existing pore systems. The ultimate goal of the task is to provide a basis for characterization of
porosity and permeability with the reef and shoal reservoirs.
Thin sections (379) are being studied from 11 cores from Appleton Field to determine the
impact of cementation, compaction, dolomitization, dissolution and neomorphism has had on the
reef and shoal reservoirs in this field. Thin sections (237) are being studied from 11 cores from
Vocation Field to determine the paragenetic sequence for the reservoir lithologies in this field. An
additional 73 thin sections are being prepared from the shoal and reef lithofacies in Vocation Field
to identify the diagenetic processes that played a significant role in the development of the pore
systems in the reservoirs at Vocation Field.
Task 3—Petrophysical and Engineering Property Characterization.--This task will
focus on the characterization of the reservoir rock, fluid, and volumetric properties of the reservoirs
at Appleton and Vocation Fields. These properties can be obtained from petrophysical and
engineering data. This task will assess the character of the reservoir fluids, as well as quantify the
petrophysical properties of the reservoir rock. In addition, considerable effort will be devoted to the
rock-fluid behavior (i.e., capillary pressure and relative permeability). The production rate and
pressure histories will be cataloged and analyzed for the purpose of estimating reservoir properties
such as permeability, well completion efficiency (skin factor), average reservoir pressure, as well as
in-place and movable fluid volumes. A major goal is to assess current reservoir pressure conditions
and develop a simplified reservoir model. New pressure and tracer survey data will be obtained to
assess communication within the reservoir at Appleton and Vocation Fields, including among and
within the various pay zones in the Smackover. This work will serve as a guide for the reservoir
simulation modeling. Petrophysical and engineering data are fundamental to reservoir
characterization. Petrophysical data are often considered static (non-time dependent) measurements,
while engineering data are considered dynamic (time-dependent). Reservoir characterization is the
coupling or integration of these two classes of data. The data are analyzed to identify fluid flow
units (reservoir-scale flow sequences), barriers to flow, and reservoir compartments. Petrophysical
data are essential for defining the quality of the reservoir, and engineering data (performance data)
are crucial for assessing the producibility of the reservoir. Coupling these concepts, via reservoir
simulation or via simplified analytical models, allows for the interpretation and prediction of
reservoir performance under a variety of conditions. The first phase of the task involves the review,
cataloging, and analysis of available core measurements and well log data. This information will be
used to classify porosity, permeability, oil and water saturations, grain density, hydrocarbon show,
and rock type for each foot of core. Core data will be correlated to the well log responses, and
porosity-permeability relationships will be established for each lithofacies evident in the available
data. The next phase involves the measurement of basic relative permeability and capillary pressure
relations for the reservoir from existing cores. These data will be compiled and analyzed and then
used for reservoir simulation and waterflood/enhanced oil recovery calculations. The third phase
focuses on the collection and cataloging of fluid property (PVT) data. In particular, basic (black oil)
fluid property data are available, where these analyses include standard measurements of gas-oil-
ratio (GOR), oil gravity, viscosity, and fluid composition. The objective of the fluid property
characterization work is to develop relations for the analysis of well performance data and for
reservoir simulation. The final phase will be to develop a performance-based reservoir
characterization of Appleton and Vocation Fields. This phase will focus exclusively on the analysis
and interpretation of well performance data as a mechanism to predict recoverable fluids and
reservoir properties. This analysis will focus on the production data, but any other well performance
data will also be considered, in particular, pressure transient test data and well
completion/stimulation data will also be analyzed and integrated into the reservoir description.
Historical pressure data will be compared to new pressure and tracer survey data for wells obtained
as part of this work. The material balance decline type curve analysis will be emphasized for the
analysis of the data.
Petrophysical and engineering property data are being gathered and tabulated. The production
history for Appleton Field and the production history for Vocation and South Vocation Fields have
been obtained and graphed (Figures 44 and 45). Water and oil saturation data for core analyses for
Appleton Field have been plotted on Figures 46 through 50. Porosity versus permeability cross
plots for wells in the fields have been prepared (Figures 51 through 54). Porosities from core
analyses have been calibrated with porosities determined from well log studies (Figures 33 through
43 and Figures 55 through 58).
Task 4—Data Integration.--This task will integrate the geological, geophysical,
petrophysical and engineering data into a comprehensive digital database for reservoir
characterization, modeling and simulation. Separate databases will be constructed for Appleton and
Vocation Fields. This task serves as a critical effort to the project because the construction of a
digital database is an essential tool for the integration of large volumes of data. This task also serves
as a means to begin the process of synthesizing concepts. The task will involve entering geologic
data and merging these data with geophysical imaging information. Individual well logs will serve
as the standard from which the data are entered and compared. The data will be entered at 1-foot
intervals. All well logs in the fields will be utilized. The researchers will resolve any apparent
inconsistencies among data sets through an iterative approach. This task also will involve entering
petrophysical data, rock and fluid property data, production data, including oil, gas and water
production, and well completion data, including perforated intervals, completion parameters, well
App
leto
n Pr
oduc
tion
0
1000
00
2000
00
3000
00
4000
00
5000
00
6000
00
7000
00
8000
00
9000
00
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
Year
Barrels (Gas in Mcf)
Wat
erG
asO
il
Figur
e 44.
Pro
ducti
on hi
story
for A
pplet
on F
ield.
By B
. J. P
anett
a.
Voca
tion
and
Sout
h Vo
catio
n Pr
oduc
tion
0
1000
00
2000
00
3000
00
4000
00
5000
00
6000
00
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1997
1998
1999
2000
2001
Year
Barrels (Gas in Mcf)
Wat
erG
asO
il
Figur
e 45.
Pro
ducti
on hi
story
for V
ocati
on an
d Sou
th Vo
catio
n Fiel
ds.
By B
. J. P
anett
a.
3986
Figure 46. Vertical plot of water saturation and oil saturation data for well permit # 3986. By Brian Panetta.
4633-B
Figure 47. Vertical plot of water saturation and oil saturation data for well permit # 4633-B. By Brian Panetta.
4835-B
Figure 48. Vertical plot of water saturation and oil saturation data for well permit # 4835-B. By Brian Panetta.
4991
Figure 49. Vertical plot of water saturation and oil saturation data for well permit # 4991. By Brian Panetta.
6247-B
Figure 50. Vertical plot of water saturation and oil saturation data for well permit # 6247-B. By Brian Panetta.
3.31 8.13 12.95 17.77 22.59
0.90 5.72 10.54 1 5.36 20.18 2 5.00
0.01
174.81
349.61
524.41
699.21
874.01
1048.80
1223.60
1398.40
1573.20
1748.00
PE R M(CA )/POR (CA ) Crossplot
Depth Interval: 12870.00 - 13027.00
Date: Wed Sep 26 09:17:20 2001
Wells:
3986
PERM
(CA)
POR (CA)
Figure 51. Cross plots of porosity versus permeability for well permit # 3986. By Brian Panetta.
3.31 8.13 12.95 17.77 22.59
0.90 5.72 10.54 1 5.36 20.18 2 5.00
0.01
174.81
349.61
524.41
699.21
874.01
1048.80
1223.60
1398.40
1573.20
1748.00
PE R M(CA )/POR (CA ) Crossplot
Depth Interval: 12860.50 - 13031.50
Date: T ue Sep 25 13:29:22 2001
Wells:
4633-B
PERM
(CA)
POR (CA)
Figure 52. Cross plots of porosity versus permeability for well permit # 4633-B. By Brian Panetta.
3.31 8.13 12.95 17.77 22.59
0.90 5.72 10.54 1 5.36 20.18 2 5.00
0.01
174.81
349.61
524.41
699.21
874.01
1048.80
1223.60
1398.40
1573.20
1748.00
PE R M(CA )/POR (CA ) Crossplot
Depth Interval: 13127.00 - 13193.00
Date: Wed Sep 26 11:30:50 2001
Wells:
PERM
(CA)
POR (CA)
4835-B
Figure 53. Cross plots of porosity versus permeability for well permit # 4835-B. By Brian Panetta.
3.31 8.13 12.95 17.77 22.59
0.90 5.72 10.54 1 5.36 20.18 2 5.00
0.01
174.84
349.67
524.50
699.33
874.16
1048.99
1223.82
1398.65
1573.48
1748.31
PE R M(CA )/POR (CA ) Crossplot
Depth Interval: 12952.50 - 13009.00
Date: Wed Sep 26 11:38:26 2001
Wells:
6247-B
PERM
(CA)
POR (CA)
Figure 54. Cross plots of porosity versus permeability for well permit # 6247-B. By Brian Panetta.
3986
Figu
re 5
5. P
oros
ity c
alib
rate
d pl
ot fo
r wel
l per
mit
# 39
86.
4633
-B
Figu
re 5
6. P
oros
ity c
alib
rate
d pl
ot fo
r wel
l per
mit
# 46
33-B
.
4835
-B
Figu
re 5
7. P
oros
ity c
alib
rate
d pl
ot fo
r wel
l per
mit
# 48
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stimulation information, etc. A validation effort will be conducted to resolve any apparent
inconsistencies among data sets through an iterative approach.
All geoscientific and petrophysical data generated to date from this study have been entered
and integrated into digital databases for Appleton and Vocation Fields for reservoir characterization,
modeling and simulation.
Work Planned for Year 2
Reservoir Description and Characterization (Phase 1)
Task 2—Rock-Fluid Interactions.--Work on this task will continue into Year 2 (Table 5).
Task 3—Petrophysical and Engineering Property Characterization.--Work on this task
will continue into Year 2.
Task 4—Data Integration.--Data resulting from Tasks 2 and 3 will be integrated into the
digital databases for Appleton and Vocation Fields during Year 2 of the project.
3-D Modeling (Phase 2)
Task 5—3-D Geologic Model.--This task involves using the integrated database which
includes the information from the reservoir characterization tasks to build a 3-D stratigraphic and
structural model(s) for Appleton and Vocation Fields. For Appleton Field, the existing, but
independently completed, geological and geophysical studies will be integrated and used in
combination with the new information from the drilling and producing of the sidetrack well in the
field and from the study of the additional five cores and additional 3-D seismic data from the field
area to revise, as needed, the current Appleton geologic model. The Appleton reef-shoal paleohigh
(low-relief) model will be applied to Vocation Field (high-relief paleohigh). The application of the
Appleton model to Vocation Field could result in the Appleton model being reasonable for
modeling the Vocation reservoir or could result in the need to modify the Appleton model to honor
the characteristics of the Vocation reservoir and structure. The result, therefore, could be a single
geologic model for reef-shoal reservoirs associated with basement paleohighs of varying degrees of
relief or two geologic models—one for reef-shoal reservoirs associated with low-relief paleohighs
and one for reef-shoal reservoirs associated with high-relief paleohighs. This task also provides the
Table 5. Milestone ChartYear 2.
Tasks S O N D J F M A M J J A
Reservoir CharacterizationTask 2—Rock Fluid Interactions
Task 3—Petrophysical & Engineering Characterization
Task 4—Data Integration
3-D ModelingTask 5—3-D Geologic Modeling
Task 6—3-D Reservoir Simulation Model
Technology TransferTask 10—Workshop
Technical ReportAnnual Report
Work Plannedxxxxx Work Accomplished
framework for the reservoir simulation modeling in these fields. Geologic modeling sets the stage
for reservoir simulation and for the recognition of flow units, barriers to flow and flow patterns in
the respective fields. Sequence stratigraphy in association with structural interpretation will form the
framework for the model(s). The model(s) will incorporate data and interpretations from sequence
stratigraphic, depositional history and structural studies, core and well log analysis, petrographic
and diagenetic studies, and pore system and petrophysical analysis. The model(s) will also
incorporate the geologic observations and interpretations made from studying stratigraphic and
spatial lithofacies relationships observed in Late Jurassic microbial reefs in outcrops. The purpose
of the 3-D geologic model(s) is to provide an interpretation for the interwell distribution of systems
tracts, lithofacies, and reservoir-grade rock. This work is designed to improve well-to-well
predictability with regard to reservoir parameters, such as lithofacies, diagenetic rock-fluid
alterations, pore types and systems, and heterogeneity. The geologic model(s) and integrated
database become effective tools for cost-effective reservoir management for making decisions
regarding operations in these fields. Accepted industry software, such as Stratamodel and GeoSec,
will be used to build the 3-D geologic model(s). GeoSec software will be used in the 3-D structural
interpretation and Stratamodel software will be used to construct the geologic model(s).
Task 6—3-D Reservoir Simulation Model.--This task focuses on the construction,
implementation and validation of a numerical simulation model(s) for Appleton and Vocation Fields
that is based on the 3-D geologic model(s), petrophysical properties, fluid (PVT) properties, rock-
fluid properties, and the results of the well performance analysis. The geologic model(s) will be
coupled with the results of the well performance analysis to determine flow units, as well as
reservoir-scale barriers to flow. Reservoir simulation will be performed separately for cases of the
Appleton and Vocation Fields to determine if a single simulation model can represent these reef-
shoal reservoirs. However, because these reservoirs are associated with basement paleohighs of
varying degrees of relief, two simulation models may be required—one for reef-shoal reservoirs
associated with low-relief paleohighs (Appleton) and one for reef-shoal reservoirs associated with
high-relief paleohighs (Vocation). The purpose of this work is to validate the reservoir model with
history-matching, then build forecasts that consider the following scenarios: 1) base case (continue
field management as is); 2) optimization of production practices (optimal well completions,
including stimulation); 3) active reservoir management (new replacement and development wells);
and 4) initiation of new recovery methodologies (targeted infill drilling program and/or possible
enhanced oil recovery scenarios). The purposes of reservoir simulation are to forecast expected
reservoir performance, to forecast ultimate recovery, and to evaluate different production
development scenarios. We will use reservoir simulation to validate the reef-shoal reservoir model,
then extend the model to predict performance for a variety of scenarios (as listed above). Our
ultimate goals in using reservoir simulation are to establish the viability of a simulation model for a
particular reservoir, then make optimal performance predictions. Probably the most important aspect
of the simulation work will be the setup phase. The Smackover is well known as a geologically
complex system, and our ability to develop a representative numerical model for both the Appleton
and Vocation Fields is linked not only to the engineering data, but also to the geological,
petrophysical, and geophysical data. We expect to gain considerable understanding regarding
carbonate reservoir architecture and heterogeneity, especially with regard to large-scale fluid flow
from our reservoir simulation work.
This task requires a setup phase which will be performed in conjunction with the creation and
validation of the integrated reservoir description. However, this work has more specific goals than
simply building the reservoir simulation model; considerable effort will go into the validation of the
petrophysical, fluid (PVT), and rock-fluid properties in order to establish a benchmark case, as well
as bounds (uncertainty ranges) on these data. In addition, well performance data will be thoroughly
reviewed for accuracy and appropriateness.
The history matching phase in this task will involve refining and adjusting data similar to
previous tasks, but in this work our sole focus will be to establish the most representative numerical
model for both the Appleton and Vocation Fields. Adjustments will undoubtedly be made to all data
types, but as a means to ensure appropriateness, these adjustments will be made in consultation and
collaboration with the geoscientists on the technical team. Our goal is to obtain a reasonable match
of the model and the field data, and to scale-up the small-scale information (core, logs, etc.) in order
to yield a representative reservoir simulation model. We will use a black oil formulation for this
work.
RESULTS AND DISCUSSION
The Project Management Team and Project Technical Team are working closely together on
this project. This close coordination has resulted in a fully integrated research approach, and the
project has benefited greatly from this approach.
Geoscientific Reservoir Characterization
Geoscientific reservoir characterization is essentially completed. The architecture, porosity
types and heterogeneity of the reef and shoal reservoirs at Appleton Field and Vocation Fields have
been characterized using geological and geophysical data.
The architecture and heterogeneities of reservoirs that are a product of a shallow marine
carbonate setting are very complex and a challenge technically to predict. Carbonate systems are
greatly influenced by biological and chemical processes in addition to physical processes of
deposition and compaction. Carbonate sedimentation rates are primarily a result of the productivity
of marine organisms in subtidal environments. In particular, reef-forming organisms are a crucial
component to the carbonate system because of their ability to modify the surrounding
environments. Reef growth is dependent upon many environmental factors, but one crucial factor is
sea-floor relief (paleotopography). In addition, the development of a reef structure contributes to
depositional topography. Further, the susceptibility of carbonates to alteration by early to late
diagenetic processes dramatically impacts reservoir heterogeneity. Reservoir characterization and
the quantification of heterogeneity, therefore, becomes a major task because of the physiochemical
and biological origins of carbonates and because of the masking of the depositional rock fabric and
reservoir architecture due to dissolution, dolomitization, and cementation. Further, the detection,
imaging, and prediction of carbonate reservoir heterogeneity and producibility is difficult because of
an incomplete understanding of the lithologic characteristics and fluid-rock dynamics that affect log
response and geophysical attributes.
Appleton Field
Based on the description of cores (8) and thin sections (379), 14 lithofacies had been identified
previously in the Smackover/Buckner at Appleton Field (Table 2). Analysis of the vertical and
lateral distributions of these lithofacies indicates that these lithofacies were deposited in one or more
of eight depositional environments: 1) subtidal, 2) reef flank, 3) reef crest, 4) shoal flank, 5) shoal
crest, 6) lagoon, 7) tidal flat, and 8) sabkha in a transition from a catch-up carbonate system to a
keep-up carbonate system. These paleoenvironments have been assigned to four
Smackover/Buckner genetic depositional systems for three-dimensional stratigraphic modeling
(Table 3). Each of these systems has been interpreted as being time-equivalent from that work, two
principal reservoir facies, reef and shoal were identified at Appleton Field.
In Year 1 of this project, we have studied the subfacies of the reef and shoal facies. Based on
the description of 11 cores (Figures 6 through 16) and 379 thin sections, three subfacies have been
recognized in the reef facies. These subfacies include thrombolitic layered, reticulate and dendroid.
Each represents a different and distinct microbial growth form which has inherent properties that
affect reservoir architecture, pore systems, and heterogeneity. The layered growth form is
characterized by a reservoir architecture that is characterized by lateral continuity and high vertical
heterogeneity. The reticulate form has a reservoir architecture that is characterized by vertical
continuity and moderate lateral heterogeneity. The dendroid form has a reservoir architecture that is
characterized by vertical and lateral continuity and low heterogeneity. The pore systems in each of
these reservoir fabrics consist of shelter and enlarged pore types. The enlargement of these primary
pores is due to dissolution and dolomitization resulting in a vuggy appearing pore system. Three
subfacies have been recognized in the shoal facies. These subfacies are the lagoon/subtidal, shoal
flank, and shoal crest. The lagoon/subtidal subfacies has a mud-supported architecture and
therefore is not considered a reservoir. The shoal flank has a grain-supported architecture but has
considerable carbonate mud associated with it, and therefore, has low to moderate reservoir capacity.
The shoal crest has a grain-supported architecture with minimal carbonate mud, and therefore, has
the highest reservoir capacity of the shoal subfacies. The pore systems of the shoal flank and shoal
crest reservoir facies consist of intergranular and enlarged pore types. The enlargement of the
primary pores is due to dissolution and dolomitization. Heterogeneity in the shoal reservoir is high
due to the rapid lateral and vertical changes in this depositional environment. Graphic logs were
constructed for each of the cores. The core data and well log signatures are integrated and calibrated
on these graphic logs (Figures 6 through 16).
Appleton Field (Figure 4) was discovered in 1983 with the drilling of the D.W. McMillan 2-14
well (permit #3854). The discovery well was drilled off the crest of a composite paleotopographic
structure, based on 2-D seismic and well data (Figure 59). The well penetrated Paleozoic basement
rock at a depth of 12,786 feet. The petroleum trap at Appleton was interpreted to be a simple
anticline associated with a northwest-southeast trending basement paleohigh. After further drilling
in the field, the Appleton structure was interpreted as an anticline consisting of two local paleohighs.
The D.W. McMillan 2-15 well (permit #6247) was drilled in 1991. The drilling of this well resulted
in the structural interpretation being revised to consist of three local paleohighs. In 1995, 3-D
seismic reflection data were obtained for the Appleton Field area. The interpretation of these data
indicated three local highs with the western paleohigh being separated into a western and a central
feature.
Based on the structural maps that we have prepared for the Appleton Field, we have concluded
that the Appleton structure is a low-relief, northwest-southeast trending ridge comprised of local
paleohighs. This interpretation is based on the construction of structure maps on top of the
basement (Figure 17), on top of the reef (Figure 18), and on top of the Smackover/Buckner (Figure
19) from 3-D seismic data. Also, maps of the basement surface (Figure 28), of the reef surface
(Figure 29) and of Smackover/Buckner surface (Figure 30) support this interpretation.
The Smackover reservoir at Appleton Field has been influenced by antecedent
paleotopography. The Smackover thickness ranges from 177 feet in the McMillan 2-14 well
(permit #3854) to 228 feet in the McMillan Trust 11-1 well (permit #3986) in the field. As
observed from the cross sections based on well log data (Figures 26 and 31) and on seismic data
(Figure 32) and on the seismic profile (Figure 27), the sabkha facies thins over the composite
2.0
2.1
2.2
2.3
2.4
2.5
2.6
2.7
Tw
o W
ay T
rave
l Tim
e (S
ec.)
2.0
2.1
2.2
2.3
2.4
2.5
2.6
2.7
North SouthT
wo
Way
Tra
vel T
ime
(Sec
.)
A.
B.
Top of Basement
Buckner/Smackover
B B '
North SouthB B '
1 mile
1 km
1 mile
1 km
Figure 59. Seismic reflection profile BB'.
paleohigh, while the reservoir lithofacies are thicker on the paleohigh. Thickness maps of the
sabkha facies (Figure 21), tidal flat facies (Figure 22), shoal complex (Figure 23), tidal flat/shoal
complex (Figure 24), and reef complex (Figure 25) facies illustrate the changes in these lithofacies
in the Appleton Field.
Vocation Field
Based on the description of cores (7) and thin sections (237), 9 lithofacies had been identified
previously in the Smackover at Vocation Field (Figure 5). These lithofacies (Table 3) include: ooid-
dominated, grain-supported; ooid-dominated, matrix-supported; oncoid-dominated, grain-
supported; oncoid-dominated, matrix-supported; peloid-dominated, grain-supported; peloid-
dominated, matrix-supported; mudstone; algal stromatolite; and algal boundstone. Analysis of the
vertical and lateral distributions of these lithofacies indicates that these lithofacies were deposited in
one or more of six depositional environments: 1) subtidal, 2) reef, 3) shoal flank, 4) shoal
crest/beach, 5) lagoon and 6) intertidal. These paleoenvironments have been assigned to four
Smackover/Buckner genetic depositional systems for three-dimensional stratigraphic modeling.
Each of these systems has been interpreted as being time-equivalent. From that work, two principal
reservoir facies, reef and shoal, were identified at Vocation Field.
In Year 1 of this project, we have studied the subfacies of the reef and shoal facies. Based on
the description of 11 cores (Figures 33 through 43) and thin sections, two subfacies have been
recognized in the reef facies. These subfacies include thrombolitic layered and reticulate. As with
the reef subfacies at Appleton Field, each represents a different and distinct microbial growth form.
The reservoir architecture, pore system, and heterogeneity for these subfacies are like those for the
same reef subfacies at Appleton Field. Three subfacies have been recognized in the shoal facies.
These subfacies are the lagoon, shoal flank and shoal crest. These shoal subfacies have a reservoir
architecture, pore system and heterogeneity similar to those for the shoal reservoir at Appleton
Field.
Vocation Field (Figure 5) was discovered in 1971 with the drilling of the B.C. Quimby 27-15
(permit #1599) well. The discovery well was drilled near the crest of a paleotopographic structure
based on 2-D seismic and well log data. The well penetrated Paleozoic basement rock at a depth of
14,209 feet. The petroleum trap at Vocation was interpreted to be an anticline associated with a
basement paleohigh.
Based on structural maps that we have prepared for the Vocation Field, we concluded that the
Vocation Field structure is a high-relief composite paleotopographic ridge. There may be as many
as eight local paleohighs associated with this paleohigh which are separated by basement troughs or
faults. The Smackover thins and, in some cases, is absent, over these features.
Rock-Fluid Interactions
The study of rock-fluid interactions have been initiated. Observation regarding the diagenetic
processes influencing pore system development and heterogeneity in these reef and shoal reservoirs
have been made.
Based on initial petrographic studies, reservoir-grade porosity in the Smackover at Appleton
field occurs in microbial boundstones in the reef interval and in oolitic, oncoidal, and peloidal
grainstones and packstones in the upper Smackover. Porosity in the boundstones is a mixture of
primary shelter porosity overprinted by secondary intercrystalline and vuggy porosity produced by
dolomitization and dissolution that is pervasive throughout the field. Porosity in the grainstones and
packstones is a mixture of primary interparticle and secondary grain moldic porosity overprinted by
secondary dolomite intercrystalline porosity.
Based on core analysis data, there is a distinct difference in reservoir quality between the
grainstone/packstone and boundstone reservoir intervals. Although the difference in reservoir
quality between these lithofacies is principally the result of depositional fabric, diagenesis acts to
enhance or impair the reservoir quality of these lithofacies. Porosity in the grainstone/packstone
reservoir interval in the McMillan 2-14 well (permit #3854) ranges from 9.7 to 21.5% and averages
14.8%. Permeability ranges from 1.1 to 618 md, having a geometric mean of 63.5 md
(Figure 60A). Porosity in the reef boundstone reservoir interval in the McMillan Trust 12-14 well
(permit #4633-B) ranges from 11.9 to 25.0% and averages 18.1%. Permeability ranges from 14 to
1748 md, having a geometric mean of 252 md (Figure 60B).
.001 .01 .1 1 10 100 1000 10000-13100
-13080
-13060
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Per meability (md)Por osity (% )
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-12960
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Shoal I nter val
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Por
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yC
uto
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Depth (ft)
A .
Per meability (md)Por osity (% )
.001 .01 .1 1 10 100 1000 10000
Shoal I nter val
R eef I nter val
Per
mea
bil
ity
Cu
toff
Figure 60. Porosity vs. depth and permeability vs. depth plots for (A) well permit # 3854 and (B) well permit # 4633-B.
The higher producibility for the reef lithofacies is attributed to the higher permeability of this
lithofacies and to the nature of the pore system (pore-throat size distribution) rather than the amount
of porosity. Pore-throat size distribution is one of the important factors determining permeability,
because the smallest pore throats in cross-sectional areas are the bottlenecks that determine the rate
at which fluids pass through a rock.
Although both the reef and shoal lithofacies accumulated in diverse environments to produce
mesoscopic-scale heterogeneity, dolomitization and dissolution acted to reduce the microscopic-
scale heterogeneity in these carbonate rocks. The grainstones/packstones accumulated in shoal
environments and were later subjected to dolomitization and vadose dissolution. The resulting
moldic pore system, which includes primary interparticulate and secondary grain moldic and
dolomite intercrystalline porosities, is characterized by multisize pores that are poorly connected by
narrow pore throats. Pore size is dependent on the size of the carbonate grain that was leached.
The boundstones accumulated in a reef environment and were later subjected to pervasive
dolomitization and nonfabric-selective, burial dissolution. The intercrystalline pore system, which
includes primary shelter and secondary dolomite intercrystalline and vuggy pores, is characterized
by moderate-size pores having uniform pore throats. The size of the pores is dependent upon the
original shelter pores, the dolomite crystal size, and the effects of late-stage dissolution. The reef
reservoir and its shelter and intercrystalline pore system, therefore, has higher producibility potential
compared to the shoal reservoir and its moldic pore system.
As confirmed from well-log analysis and well production history, hydrocarbon production in
Appleton field has occurred primarily from the boundstones of the Smackover reef interval, with
secondary contributions from the shoal grainstones and packstones of the upper Smackover. Total
reservoir thickness in the producing wells ranges from 20 ft (6 m) in the McMillan Trust 11-1 well
(permit #3986) to 82 ft (25 m) in the McMillan Trust 12-4 well (permit #4633-B). With the
exception of the McMillan 2-14 well (permit #3854), where production has been primarily from
grainstones and packstones of the upper Smackover, the majority of the productive reservoir occurs
in boundstones.
The higher production from the reef interval is attributed to the better reservoir quality of the
boundstones and to the better continuity and connectivity of these carbonates. Whereas, the
grainstone/packstone interval is discontinuous, both vertically and laterally, the boundstone interval
appears to possess excellent vertical and lateral continuity.
In addition, although the microbial reef reservoir interval is more productive than the shoal
reservoir interval at Appleton Field, the dendroidal thrombolites have higher reservoir quality than
the layered thrombolites (Figure 61). Dendroidal thrombolites have a reservoir architecture
characterized by high lateral and vertical pore interconnectivity and permeability, while layered
thrombolites have good lateral but poorer vertical pore interconnectivity and permeability. Both
thrombolite architectures are characterized by pore systems comprised of shelter and enlarged
pores.
Petrophysical and Engineering Property Characterization
Initial results from work related to this task show that Appleton (Figure 44) and Vocation and
South Vocation Fields (Figure 45) have experienced a substantial decline in oil production since
their initial discoveries. To date, petrophysical characterization of the reservoir properties has
consisted of tabulating water and oil saturations (Figures 46 through 50), preparing porosity versus
permeability cross plots for wells in the fields (Figures 51 through 54) and calibrating porosities
resulting from core analyses to those observed from well logs (Figures 55 through 58). These
graphs and data are in agreement with the geoscientific characterization results in that the reef
reservoirs consistently have higher reservoir quality than the shoal reservoirs.
Data Integration
All geoscientific and petrophysical data generated to date from this study have been entered
and integrated into digital databases for Appleton and Vocation Fields for reservoir characterization,
modeling and simulation.
0.01
0.1
1
10
100
1000
10000
0 10 20 30 40
permeability(md)
porosity(percent)
Layered thrombolite Dendroidal thrombolite
Figure 61. Reservoir quality of thrombolitic facies.
CONCLUSIONS
The University of Alabama in cooperation with Texas A&M University, McGill University,
Longleaf Energy Group, Strago Petroleum Corporation, and Paramount Petroleum Company are
undertaking an integrated, interdisciplinary geoscientific and engineering research project. The
project is designed to characterize and model reservoir architecture, pore systems and rock-fluid
interactions at the pore to field scale in Upper Jurassic Smackover reef and carbonate shoal
reservoirs associated with varying degrees of relief on pre-Mesozoic basement paleohighs in the
northeastern Gulf of Mexico. The project effort includes the prediction of fluid flow in carbonate
reservoirs through reservoir simulation modeling which utilizes geologic reservoir characterization
and modeling and the prediction of carbonate reservoir architecture, heterogeneity and quality
through seismic imaging.
The primary objective of the project is to increase the profitability, producibility and efficiency
of recovery of oil from existing and undiscovered Upper Jurassic fields characterized by reef and
carbonate shoals associated with pre-Mesozoic basement paleohighs.
The principal research effort for Year 1 of the project has been reservoir description and
characterization. This effort has included four tasks: 1) geoscientific reservoir characterization,
2) the study of rock-fluid interactions, 3) petrophysical and engineering characterization and 4) data
integration. This work was scheduled for completion in Year 1.
Geoscientific reservoir characterization is essentially completed. The architecture, porosity
types and heterogeneity of the reef and shoal reservoirs at Appleton and Vocation Fields have been
characterized using geological and geophysical data. All available whole cores (11) from Appleton
Field have been described and thin sections (379) from these cores have been studied. Depositional
facies were determined from the core descriptions. The thin sections studied represent the
depositional facies identified. The core data and well log signatures have been integrated and
calibrated on graphic logs. For Appleton Field, the well log, core, and seismic data have been
entered into a digital database and structural maps on top of the basement, reef, and
Smackover/Buckner have been constructed. An isopach map of the Smackover interval has been
prepared, and thickness maps of the sabkha facies, tidal flat facies, shoal complex, tidal flat/shoal
complex, and reef complex have been prepared. Maps have been constructed using the 3-D seismic
data that Longleaf contributed to the project to illustrate the structural configuration of the
basement surface, the reef surface, and Buckner/Smackover surface. Petrographic analysis and pore
system studies have been initiated and will continue into Year 2 of the project.
All available whole cores (11) from Vocation Field have been described and thin sections (237)
from the cores have been studied. Depositional facies were determined from the core descriptions.
From this work, an additional 73 thin sections are being prepared to provide accurate representation
of the lithofacies identified. The core data and well log signatures have been integrated and
calibrated on the graphic logs. The well log and core data from Vocation Field have been entered
into a digital database and structural and isopach maps are being constructed using these data. The
graphic logs are being used in preparing cross sections across Vocation Field. The core and well
log data are being integrated with the 3-D seismic data that Strago contributed to the project.
Petrographic analysis and pore system studies have been initiated and will continue into Year 2 of
the project.
The study of rock-fluid interactions has been initiated. Thin sections (379) are being studied
from 11 cores from Appleton Field to determine the impact of cementation, compaction,
dolomitization, dissolution and neomorphism has had on the reef and shoal reservoirs in this field.
Thin sections (237) are being studied from 11 cores from Vocation Field to determine the
paragenetic sequence for the reservoir lithologies in this field. An additional 73 thin sections are
being prepared from the shoal and reef lithofacies in Vocation Field to identify the diagenetic
processes that played a significant role in the development of the pore systems in the reservoirs at
Vocation Field.
Petrophysical and engineering property characterization is progressing. Petrophysical and
engineering property data are being gathered and tabulated. The production history for Appleton
Field and the production history for Vocation and South Vocation Fields have been obtained and
graphed. Water and oil saturation data for core analyses for Appleton Field have been tabulated.
Porosity versus permeability cross plots for wells in the fields have been prepared, and porosities
from core analyses have been calibrated with porosities determined from well log studies.
Data integration is on schedule, in that, geological, geophysical and engineering data collected
to date for Appleton and Vocation Fields have been compiled into a fieldwide digital database for
reservoir characterization, modeling and simulation for the reef and carbonate shoal reservoirs for
each of these fields.
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Benson, D.J., 1985, Diagenetic controls on reservoir development and quality, Smackover
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Benson, D.J., 1988, Depositional history of the Smackover Formation in southwest Alabama: Gulf
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