Improving Reservoir Characterization Improving Reservoir Characterization of Karst-Modified Reservoirs of Karst-Modified Reservoirs

with 3-D Geometric Seismic Attributes with 3-D Geometric Seismic Attributes

Susan E. NissenSusan E. Nissen11, E. Charlotte Sullivan, E. Charlotte Sullivan22, , Kurt J. MarfurtKurt J. Marfurt33, and Timothy R. Carr, and Timothy R. Carr44

11Consultant, McLouth, KSConsultant, McLouth, KS22Pacific Northwest National Labs, Richland, WAPacific Northwest National Labs, Richland, WA

33College of Earth and Energy, University of Oklahoma, Norman, OKCollege of Earth and Energy, University of Oklahoma, Norman, OK44Department of Geology and Geography, West Virginia University, Department of Geology and Geography, West Virginia University,

Morgantown, WVMorgantown, WV

OutlineOutline

• Characteristics of karst-modified reservoirsCharacteristics of karst-modified reservoirs

• Multi-trace geometric seismic attributes Multi-trace geometric seismic attributes

• Seismic-based examples of Seismic-based examples of • Collapse structuresCollapse structures

• Polygonal featuresPolygonal features

• Oriented lineamentsOriented lineaments

• Interpretation workflow for karst-modified Interpretation workflow for karst-modified reservoirsreservoirs

• ConclusionsConclusions

Karst Modified Reservoirs

• Carbonate reservoirs Carbonate reservoirs

• Rocks modified by dissolution during Rocks modified by dissolution during subaerial exposuresubaerial exposure

• May also have hydrothermal and tectonic May also have hydrothermal and tectonic overprintsoverprints

Examples of karst features that can affect Examples of karst features that can affect reservoir performancereservoir performance

Cave collapse facies in image logFt. Worth Basin, Texas

Collapse features Solution-enlarged Solution-enlarged fracturesfractures

Loess-filled fractures, Missouri

• Fluid conduits (if Fluid conduits (if open) or barriers open) or barriers (if filled) (if filled)

Cockpit karst, Jamaicawww.cockpitcountry.com

Residual Residual paleo-highspaleo-highs

• May be hydro-May be hydro- carbon traps carbon traps

• CompartmentalizeCompartmentalize reservoir reservoir • Affect depositionAffect deposition of overlying strata of overlying strata

Interpretation of Karst FeaturesInterpretation of Karst Features

• Well data alone is insufficient for identifying the Well data alone is insufficient for identifying the spatial extent and distribution of local karst features. spatial extent and distribution of local karst features.

• Karst features with substantial vertical relief can be Karst features with substantial vertical relief can be readily identified using 3-D seismic. readily identified using 3-D seismic.

• Critical features relating to reservoir character are Critical features relating to reservoir character are often often subtlesubtle and not readily detected using standard and not readily detected using standard 3-D seismic interpretation methods.3-D seismic interpretation methods.

• Multi-trace geometric seismic attributes can help!Multi-trace geometric seismic attributes can help!

Multi-Trace Geometric Seismic Attributes Multi-Trace Geometric Seismic Attributes

• Calculated using multiple input seismic traces Calculated using multiple input seismic traces and a small vertical analysis windowand a small vertical analysis window

• The analysis "box" moves throughout the entire The analysis "box" moves throughout the entire data volume => attributes can be output as a 3-data volume => attributes can be output as a 3-D volumeD volume

• Provide quantitative information about lateral Provide quantitative information about lateral variations in the seismic data variations in the seismic data

Multi-Trace Geometric Seismic Attributes Multi-Trace Geometric Seismic Attributes

• CoherenceCoherence - A measure of the trace-to-trace similarity of - A measure of the trace-to-trace similarity of the seismic waveformthe seismic waveform

• Dip/azimuthDip/azimuth - Numerical - Numerical estimation of the estimation of the instantaneous dip and instantaneous dip and azimuth of reflectors azimuth of reflectors

• CurvatureCurvature – A measure of the – A measure of the bending of a surface (~2bending of a surface (~2ndnd derivative of the surface)derivative of the surface)

PositiveCurvature

ZeroCurvature

ZeroCurvature

DippingPlane

Anticline

Syncline

NegativeCurvature

Flat

Z

X

After Roberts, 2001

PositiveCurvature

ZeroCurvature

ZeroCurvature

DippingPlane

Anticline

Syncline

NegativeCurvature

Flat

Z

X

PositiveCurvature

ZeroCurvature

ZeroCurvature

DippingPlane

Anticline

Syncline

NegativeCurvature

Flat

Z

X

Z

X

After Roberts, 2001Curvature (k)=1/R

R

Reference TraceReference Trace

Instantaneous dip =Instantaneous dip =Dip with highest Dip with highest coherencecoherence

Dips Dips testedtested

Central Kansas Uplift

Mid Continent examplesMid Continent examples

- Collapse structures- Collapse structures - Polygonal features - Polygonal features - Oriented lineaments - Oriented lineaments

Ord. Arbuckle

Ft. Worth Basin Ord. Ellenburger

Mississippian

Pennsylvanian Caddo

Ordovician Ellenburger

~2600 ft

Collapse Features – Fort Worth Basinvertical seismic section

Collapse features

• Collapse features Collapse features are visible asare visible asdepressions on thedepressions on the3-D seismic profile3-D seismic profile

• Collapse features Collapse features extend from theextend from theEllenburger through Ellenburger through

Pennsylvanian Pennsylvanian stratastrata

Attribute time slices near the EllenburgerAttribute time slices near the Ellenburger

N

EW

S

3 mi

Dip/Azimuth Most Negative Curvature

Amplitude Coherence

Collapse Collapse featuresfeatures

faultfault

Collapse features line up at the intersections of negative curvature lineaments

Time = 1.2 s1 mi

Most Negative CurvatureMost Negative CurvatureCoherenceCoherence

Polygonal FeaturesPolygonal Features

Ordovician ArbuckleOrdovician ArbuckleKansasKansas

Ordovician EllenburgerOrdovician EllenburgerFort Worth BasinFort Worth Basin

1 mi1.6 km

1 mi1.6 km 1 mi

1.6 km

Diameters ~700-900 ftDiameters ~700-900 ft Diameters ~1400-1600 ftDiameters ~1400-1600 ft Diameters ~1200 -3500 ftDiameters ~1200 -3500 ft

Vertical relief generally 2 ms (~15 ft) or lessVertical relief generally 2 ms (~15 ft) or less

Arbuckle Polygonal KarstArbuckle Polygonal Karst-- Cockpit Karst-- Cockpit Karst

Morphological map Morphological map of karst area in New of karst area in New Guinea (Guinea (Williams, Williams,

19721972))

Cockpits

(After Cansler and Carr, 2001)

Cockpit karst

Arbuckle time structure Arbuckle time structure overlain by most positive overlain by most positive

curvaturecurvature

1 mi1.6 km

Arbuckle structure overlain Arbuckle structure overlain with paleotopographic with paleotopographic divides in Barton Co., KS divides in Barton Co., KS ((Cansler, 2000Cansler, 2000))

doline

cone

N

Faults

Ellenburger polygonal karst - tectonic collapse structures

Collapse feature at topographic high

Basement

Ellenburger

Collapse Features Coincide with Deep Basement Faults

0.5 mile

Oriented lineaments -- Kansas MississippianOriented lineaments -- Kansas Mississippian

0

10

20

30

40

50

60

70

80

90

100

0 100 200 300 400 500 600 700 800

distance to NW lineament (ft)

5 ye

ar w

ater

pro

duct

ion

(x10

4 Bbl

)

0

2

4

6

8

10

12

14

0 100 200 300 400 500 600 700 800

distance to NW lineament (ft)

5 ye

ar o

il pr

oduc

tion

(x10

4 Bbl

)

Lineament trend vs.Lineament trend vs.oil/water productionoil/water production

0

10

20

30

40

50

60

70

80

90

100

0 100 200 300 400 500 600 700 800

distance to NE lineament (ft)

5 ye

ar w

ater

pro

duct

ion

(x10

4 Bbl

)

0

2

4

6

8

10

12

14

0 100 200 300 400 500 600 700 800

distance to NE lineament (ft)

5 ye

ar o

il pr

oduc

tion

(x10

4 Bbl

)

Workflow for Identification of Karst OverprintsUsing Multi-Trace Attributes

Interpret features relating to structure, geomorphology, and reservoir architecture

on attribute slices

Extract attributesalong horizon or time slice

Measure distance from oriented lineaments.

Outline potential reservoircompartment boundaries

(fluid barriers)

Identify areas of enhanced or occluded porosity/permeability

Separate subaerial karst from tectonic overprint

Core andlog data

Horizonpicks

Predict general production performance based on type of karst overprint

Volumetricattributes

Identify dominant karst geomorphology (e.g., polygonalkarst vs. groundwater-sapped

plateaus)

Productiondata

Identify preferred orientations of fluid conduits vs. barriers

• Coherence, dip/azimuth, and curvature Coherence, dip/azimuth, and curvature extractions are valuable for establishing seismic extractions are valuable for establishing seismic geomorphologygeomorphology

• Different attributes reveal different details about Different attributes reveal different details about karst featureskarst features

• A workflow utilizing multi-trace attributes, along A workflow utilizing multi-trace attributes, along with geologic and production information, can with geologic and production information, can improve characterization of karst-modified improve characterization of karst-modified carbonate reservoirscarbonate reservoirs

ConclusionsConclusions

AcknowledgementsAcknowledgements

Devon EnergyDevon Energy Grand Mesa Operating CompanyGrand Mesa Operating Company John O. Farmer, Inc.John O. Farmer, Inc. Murfin Drilling CompanyMurfin Drilling Company IHS - geoPLUS CorporationIHS - geoPLUS Corporation Seismic Micro-Technology, Inc.Seismic Micro-Technology, Inc. U. S. Department of EnergyU. S. Department of Energy Petroleum Research FundPetroleum Research Fund State of Texas ATPState of Texas ATP Kansas Geological Survey, University of KansasKansas Geological Survey, University of Kansas University of HoustonUniversity of Houston