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Geomechanical Performance of Hydrate-Bearing Sediments in Offshore Environments

Schlumberger PlansRichard A. PlumbN.E.T.L, Morgantown W.Va.January 19, 2007

© 2006 Schlumberge All rights reserved.

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Objectives

Develop the capability of building 4D Geomechanical models of the near-seafloor deep-marine hydrate-bearing sediments.

Interface Petrel framework model with FLAC3D

Develop 4D geomechanics models of the near-wellbore region of hydrate-bearing deep-marine sediments

© 2006 Schlumberge All rights reserved.

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Scope of work 2006

H1 2006Review the geological structures on the U.S. continental margins characteristic of the gas hydrate stability zone (GHSZ).Determine whether Petrel’s framework modeling tools can reproduce realistic fault and sedimentary structures of the (GHSZ)

H2 2006Evaluate the capability to interface Petrel with FLAC3DRecommend improvements to Petrel developersContract ITASKA to interface Petrel to 3DShop and FLAC3DSelected Keathley Canyon as a field test siteBuild a small Petrel modelExported Petrel surfaces and geological properties to ITASKA software

© 2006 Schlumberge All rights reserved.

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Geological environment

~ Hydrate Stability Zone

Complex structure due to salt diapirism

© 2006 Schlumberge All rights reserved.

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Gulf of Mexico Gas Hydrates Joint Industry Participation Project

Petrel ModelPetrel Model

© 2006 Schlumberge All rights reserved.

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Modelling challenges seen in seismic section at Keathley Canyon

BSR

PossibleHydrate mound

Waterbottom4260 feet BMSLClays, coarsergrained lenses,slope fans.

Sand-shales,channel levee systems.

LST slope fans,channeling, slopefailures, chaoticevents.

unconformity

HST

HST

LST

HST

LST

Unconfomity

Sand-shalelaminates, slopefan deposits.

HST shales andsand layer laminates.

LST

SBSB

SB

SB

?

Keathley Canyon Inline 5591

Pleist1

Line 5591

Depth TVDSS(ft)

4694

5254

5823

6445

7108

BSR

PossibleHydrate mound

Waterbottom4260 feet BMSLClays, coarsergrained lenses,slope fans.

Sand-shales,channel levee systems.

LST slope fans,channeling, slopefailures, chaoticevents.

unconformity

HST

HST

LST

HST

LST

Unconfomity

Sand-shalelaminates, slopefan deposits.

HST shales andsand layer laminates.

LST

SBSB

SB

SB

?

Keathley Canyon Inline 5591

Pleist1

Line 5591

BSR

PossibleHydrate mound

Waterbottom4260 feet BMSLClays, coarsergrained lenses,slope fans.

Sand-shales,channel levee systems.

LST slope fans,channeling, slopefailures, chaoticevents.

unconformity

HST

HST

LST

HST

LST

Unconfomity

Sand-shalelaminates, slopefan deposits.

HST shales andsand layer laminates.

LST

SBSB

SB

SB

?

Keathley Canyon Inline 5591

Pleist1

Line 5591

Depth TVDSS(ft)

4694

5254

5823

6445

7108

Depth TVDSS(ft)

4694

5254

5823

6445

7108

4694

5254

5823

6445

7108

Faults

Unconformities & Pinchouts

Salt bodies

Hydrate mounds

Discordant contacts-e.g. BSR

© 2006 Schlumberge All rights reserved.

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Geomechanical Property Modelling Workflow

PetrelProperty Modeling

PetrelProperty Modeling

Vp

Bulk Density

Pp

GeophysicalLogs

3D seismic volumes (time domain)

Framework model

Bulk density

Lithology

Porosity

Elastic parameters

Strength parameters

Pp

FLAC3DGeomechanics

Simulator

FLAC3DGeomechanics

Simulator

3D geo-property volumes (depth domain)

PetrelProperty Modeling

PetrelProperty Modeling

VpVp

Bulk DensityBulk Density

PpPp

GeophysicalLogs

3D seismic volumes (time domain)

Framework model

Bulk density

Lithology

Porosity

Elastic parameters

Strength parameters

Pp

Framework modelFramework model

Bulk densityBulk density

LithologyLithology

PorosityPorosity

Elastic parametersElastic parameters

Strength parametersStrength parameters

PpPp

FLAC3DGeomechanics

Simulator

FLAC3DGeomechanics

Simulator

3D geo-property volumes (depth domain)

Interactive, Seismic volume extraction

Digitize faults in,3D Seismic volume

Model complexgeobodies

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Keathley Canyon Horizons in Petrel

© 2006 Schlumberge All rights reserved.

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Keathley Canyon- preliminary bulk density volume

Gardner’s relationship: RhoB= a(Vp)^b

Coefficients for mudstone: a=1.75, b=0.265

Coefficients for sandstone: a=1.66, b=0.261

© 2006 Schlumberge All rights reserved.

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Simplifiled Keathley Canyon model in Petrel

Faults are not explicitly modeled in ITASKA’s initial surfaces data set

© 2006 Schlumberge All rights reserved.

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ITASKA’s Modelling Workflow

PETREL

Base3DShop

FLAC3D

Local Octree Refinement

Zmap Translator

Volume Property Translator

Result

Reads volume properties from the grid file and assigns them to individual FLAC3D zones

Translates Zmapfiles into triangular patches in 3DShop

Uses an Octree method to refine a coarse mesh in areas of interest

PETREL

Base3DShop

FLAC3D

Local Octree Refinement

Zmap Translator

Volume Property Translator

Result

Reads volume properties from the grid file and assigns them to individual FLAC3D zones

Translates Zmapfiles into triangular patches in 3DShop

Uses an Octree method to refine a coarse mesh in areas of interest

© 2006 Schlumberge All rights reserved.

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Geologic Horizons in ITASKA’s 3DShop

© 2006 Schlumberge All rights reserved.

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Proposed Next Steps 2007

ITASKARead Petrel property volumeDesign the software interfacePerform a sample geomechanical calculation in FLAC3D

SchlumbergerRefine the input velocity modelIntroduce well log data and perform log-guided seismic inversionConstruct geomechanical property volumesPerform a sample geomechanical calculation in FLAC3D

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Questions/Discussion