Tim Carr - West Virginia University

Source Rock

Migration Route

Reservoir Rock

Seal Rock

Trap

Elements

Generation

Migration

Accumulation

Preservation

Processes

2

Reservoir Porous & Permeable Rock Suitable for Production Most Commonly Sandstone & Carbonate

What is the Volume of Hydrocarbons? Percentage of Pores versus Matrix Percentage of Pore Occupied by Hydrocarbons

Hydrocarbon Saturation

What is the Production Rate? Permeability – Ease of Flow

What is the Geometry of the Reservoir? Internal Geometry - Sweep External Geometry – More Hydrocarbons in Vicinity

Can We Provide Input to Models of the Reservoir? Static Geomodel Dynamic Fluid Flow Model Field Management & Enhancement

A “Container” From Which

Oil & Gas

Can Be

Produced

3

Primary (original)

Secondary (induced) (Generally more complex than

primary porosity)

4

Additional open space developed after

sedimentation: Cementation

Dissolution

Dolomitization

Fracturing

5

POROSITY IN SANDSTONE

MATRIX

FRAMEWORK (QUARTZ)

FRAMEWORK (FELDSPAR)

CEMENT

PORE

Note different use of “matrix”

by geologists and engineers 0.25 mm

Sandstone Comp.

• Framework

• Matrix

• Cement

• Pores

DISSOLUTION

PORE

FRACTURE

1. Primary and secondary “matrix” porosity system

2. Fracture porosity system

6

MORE POROUS LESS POROUS

7

Ohio Outcrop 8

Gloades Corner Reservoir, NY

9

Photo: J. Olson, UT Austin

10

11

Photo: J. Olson, UT Austin 12

Photo: J. Olson, UT Austin 13

Photo: J. Olson, UT Austin 14

(Smosna, 1996) (Gas Atlas)

Example of Fractured Carbonate Reservoir

Burgoon Sandstone

Formation

Green

brie

r L

imest

on

e

Big Lime

Big InjunLoyalhanna

Member

Gre

enbrier

Lim

esto

ne

Keener SS

Pocono Formation Pocono Formation

McCrady Formation

Upper

Member

Unnamed Shale

Sandstone

Upper

Member

Wymps

Gap

Member

Savage Dam

Deer Valley

Mauch C

hunk F

orm

ation

Maxville Limestone

Bluefield Maxton Sandstone Mauch Chunk

Pickaway

Taggard

Denmar

Reynolds

Member

Lillydale

Member

Hillsdale

PennsylvaniaEastern Ohio

Alderson

Union

Formation

West Virginia

Subsurface

Little Lime

Pencil Cave Shale

Northern West VirginiaSoutheast West

Virginia

Reynolds

Lillydale

Loyalhanna Limestone

MIS

SIS

SIP

PIA

N

MID

DL

E

LO

WE

R

AGE

UP

PE

R

Maccrady Fm

primary fault play target

15

Isopach of Union Oolite, Rhodell Field

Area

(from Gas Atlas)

study area

16

Sparks and Ayers, unpublished

CORE PLUG

17

3527’ scale in cm

ooids

3527’

intragranular porosity (blue)

1 mm

3527’

oolite rim (8% porosity)

sparry calcite (poor porosity)

2000’

200

0’

Scale:

Estimated Ultimate Recovery (EUR) Map

C.I. = 200 MMcf

21

2000’

200

0’

Scale:

UNION OOLITE

NET PAY ISOPACH

Porosity > 4%

C.I. = 4’

#5834

#5638

22

Cross-Section A – A’

A A’

0

-500

-1000

-1500

PILOT KNOB

ARISTA

NW SE

Scale:

500’

500

’

UNION

PICKAWAY

DENMAR

LITTLE LIME

PRICE

2000’

200

0’

A

A’ 23

DEPI #5834 (047-055-00238)

UNION OOLITE (Hanging wall)

UNION OOLITE (Foot wall)

PILOT KNOB THRUST FAULT

206’ OFFSET

OPEN FRACTURES 30 MMcf natural

50’

24

DEPI #5834 047-055-00238

FMI LOG

open fracture

drilling induced fractures

DEPI #5834 (047-055-00238)

SIDEWALL CORES

50’

PILOT KNOB THRUST FAULT 206’ OFFSET

26

OPEN FRACTURES – DEPI #5834 (FAULT ZONE)

Highly deformed interval Strike: NNE – SSW Dips: 30-50° 27

3446.5’ scale in cm

open fracture

28

300μm micritized ooids

3446.5’

open fracture

3446.5’

open fracture

authigenic, euhedral quartz crystals

3477’ scale in cm

calcite filled vugs & fractures

31

(after Nelson, 2001) no scale

UNION OOLITE THRUST MODEL WITH FRACTURE SWARM

UNION OOLITE

32

Avg Mcf/d

0

50

100

150

200

250

300

350

400

450

11/5/01 5/24/02 12/10/02 6/28/03 1/14/04 8/1/04

FAULT WELL PRODUCTION (outside Oolite trend)

DEPI #5834 (047-055-00238)

Lesser decline (reservoir production)

Steep initial decline (fracture production)

(30 MMcf natural)

33

How should we manage the field so as to maximize our investments?

Can we monitor how oil is being swept out of the reservoir?

What about injection wells and enhanced recovery?

Is there more oil in the vicinity – either at deeper depths or in nearby traps?

Can we contribute to a computer model of the field that matches existing production data? If so, we can test future recovery with different drilling scenarios. 34

Add reserves (volumes)

New discoveries

More from discovered producing zones

Additional producing zones

Get the most reserves at the lowest cost

Invest in the right basins

Drill in the optimum locations

Correctly assess what can be recovered

Avoid unnecessary wells 35

Modified from ExxonMobil 36

Courtesy of ExxonMobil

Geologic Model

Reservoir Simulation

Oil

Pro

du

cti

on

Production Time

HISTORY MATCH

Actual in Blue

Modeled in Red

37

Courtesy of ExxonMobil

An integration of all geologic, geophysical, petrophysical and interpreted or conceptual information about a reservoir into a single 3D numerical description of that reservoir

Structural Interpretation

Stratigraphic

Interpretation

Petrophysical Interpretation

Geophysical Interpretation

38

Courtesy of ExxonMobil

Each cell can be populated with rock & fluid Properties:

– Facies

– Porosity

– Permeability

– Fluid Saturation

– Etc.

1m

39

Courtesy of ExxonMobil

How do we use this information?

• Field development planning

• Field production optimization

• Reservoir surveillance

HistoryO

il R

ate

Time

Prediction

EOR

Infill Drilling

Oil

Rat

e

Time

Base Case

HistoryO

il R

ate

Time

HistoryO

il R

ate

Time

HistoryO

il R

ate

Time

Oil

Rat

e

Time

Prediction

EOR

Infill Drilling

Oil

Rat

e

Time

Base Case

Prediction

EOR

Infill Drilling

Oil

Rat

e

Time

Base Case

EOR

Infill Drilling

Oil

Rat

e

Time

Base Case

Time (yrs)

Oil

Ra

te

Time (yrs)

Oil

Ra

te

History

Oil

Rat

e

Time

Prediction

EOR

Infill Drilling

Oil

Rat

e

Time

Base Case

History

Oil

Rat

e

Time

History

Oil

Rat

e

Time

History

Oil

Rat

e

Time

Oil

Rat

e

Time

Prediction

EOR

Infill Drilling

Oil

Rat

e

Time

Base Case

Prediction

EOR

Infill Drilling

Oil

Rat

e

Time

Base Case

EOR

Infill Drilling

Oil

Rat

e

Time

Base Case

Actual

Modeled

40

Matrix Permeability

Fracture Permeability 41

Matrix Permeability

Fracture Permeability

Distributed Fracture Network

42

43

Take Home Ideas

Secondary Porosity Importance of Fracture Porosity

Permeability Ease of Flow Through a Rock

Related to Size of Pore and Pore Throats

Absolute and Relative Permeability

Volume of Hydrocarbons and Rate of Flow of Hydrocarbons Determines Economic Potential

Reservoir Simulation Develop Static Geomodel

Assist in Maximizing Profit

44

Assignments Reading for this week

Exploring for Oil and Gas Traps p. 17-22 & 38-43

Read Today in Energy for Tuesday (2/24) at http://www.eia.gov/

Be Prepared to Discuss in Class - Wednesday

Discussion Leader – Alexis Johnson

Test on Friday 2/27 During Class – Multiple Choice, True/False,

Short Essays