CCS and Geomechanics: A Review of Workflows and Some …€¦ · Geomechanics has a crucial role to play in understanding the containment of a storage complex ... Reservoir Stress

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CCS and Geomechanics: A Review of Workflows and Some Key Technical Challenges

Mark DavisonShell International Petroleum Company Ltd

Aberdeen, UK

IEAGHG Meeting: Modelling of CO2 Geological Storage and Wellbore Integrity27-29 April, 2011

Perth, Australia

Acknowledgements:

Martin Jagger, Max Prins

Joel Ita, Sietse de Vries, Ashok Shinde, Peter Schutjens


Outline

� Introduction to Goldeneye Project

� Brief Review of Geomechanics and CCS projects

� What GM has got to offer for CCS projects...

� CCS project workflows and geomechanics

� CCS and Geomechanics: Challenges and Technical Gaps

1. Impact of faults and fractures

2. Impact of temperature

3. Impact of reservoir pressure depletion and inflation

4. Chemical reactions and geomechanical properties

� Goldeneye Example: Key Challenge

� Concluding remarks

2


The Longannet to Goldeneye Project is a complete end-to-end solution

3

CO2 piped to St Fergus Gas Terminal using existing National Grid gas pipeline

CO2 stored in the depleted gas reservoir, injecting via existing platform wells

Carbon capture technology provided by Aker Clean Carbon, already tested on site with mobile pilot plant

CO2 transported to Goldeneye field using existing101 km offshore pipeline

CO2 extracted from flue gas at Scottish Power’s 2.4 GW coal-fired Longannet Power Station


Potential routes for loss of containment

1. Fracturing Caprock /

Seals *

2. Spill-point

3. Diffusion through seal

4. Migration along

faults/fractures*

5. Migration along wells (*)

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2

4

4

5

* Where Geomechanics

has a critical Impact


CCS Workflow and Geomechanics

� What can Geomechanics do for CCS projects?� Assessment of containment

� Caprock / seals and their integrity

� Potential for injection-induced fault reactivation and seismic events

� Reservoir response to CO2 (deformation)

� Reservoir deformation and surface movement

� Design of monitoring program

� Risk of reservoir compartmentalisation

� Operational guidance

� Predicted maximum injection pressure

� Predict hydraulic fracture propagation pressure and risk of breakthrough

� Wells

� Location and design of wells

� Sand control and completion strategy

� Life-cycle well integrity

17 May 2011 5

GM Activity

Source: DNV


Workflow for Geomechanical Input to CCS Projects

6

Objectives

Tasks

Data

Tools

ORP Stage

Software Applications


Workflow Example: ‘Define Stage’

7

Technical

Subsurface

Objectives

Geomechanical

Tasks

Data

Requirements

Tools

EG: Goldeneye Project, UK

Na

�

�

�

�

�

�

Na

��

�Na

�


CCS and Geomechanics: Technical Gap #1

� Fault Leakage Prediction

� Scenario: Containment of CO2 in reservoirs where faults have been identified in caprock.

� Issue – Some risk analysis of fault reactivation can be carried out using geomechanical tools,

however, there is a distinct lack of data (in industry) available to show the impact of this.

� Detail – We need to be able to predict the risk of leakage associated with fault reactivation

predictions made using geomechanical tools and techniques. The impact of CO2 and fault zone

interaction is potentially significant and will change with time.

8

Coulomb Slip Tendency on a fault plane



9

� Thermal Response

� Scenario: Significant cooling of the reservoir and (locally) the caprock occurs due to CO2 injection and plume development.

� Issue – Adjacent to injection wells, local cooling of the reservoir and caprock will enhance

tensile and shear failure which could jeopardise containment.

� Detail – Even though geomechanical modelling of the ‘scaled up’ reservoir shows minimal risk

of loss of containment, there is very limited data and understanding of localised cooling induced

shear failure of rocks, both in terms of the rock thermal response and the affect this has on the

failure behaviour.

σΗ

σh

Cook et al, 2006



� Reservoir Stress Path

� Scenario: Injection of CO2 into a previously depleted reservoir.

� Issue – The effective in-situ stresses are directly

impacted by the reduction and then the inflation in

reservoir pressure.

� Detail - We (industry) have a reasonable

understanding of the depletion scenario in terms of the

coupling between the in-situ stress and pore pressure,

however, there is distinct paucity of data showing what

happens with reservoir pressure inflation. This is of

major importance if we want to understand whether we

are injecting CO2 under matrix or fracturing

conditions, as well as issues such as fault reactivation

and surface deformation.

� Risk Mitigation: XLOT

10



11

� Alteration of rock mechanical properties with time� Scenario: Injected CO2 can react with mineral phases present in reservoir and caprock

� Issue – Rock mechanical material properties affected by interaction with CO2 over time

� Detail – Chemical disequilibria imposed by introduction of CO2 into reservoir both dissolves

and/or precipitates mineral phases. Geomechanical modelling is required to account for the

changes in rock properties with time to gauge the impact these processes have on containment.

� Risk Mitigation: Core tests

Modified from Johnson et al, 2004


Goldeneye Key Challenge...Thermoelasticity and fracture propagation

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20° C

83° C

4282 psi

6458 psi

Minimum

Principal

Stress

Temperature

3150 psi

3900 psi

Predicted

Pinjection

time

Pressure

Rodby Caprock

Captain Sand Reservoir

σt = E x αt x ∆T /(1-ν)

� Typical water/fluid injection simulation� Thermal response only linked to where fluid leak-off occurs, ie reservoir

� No account of thermal behaviour with caprock shale� Requires coupled thermal modeling and fracture propagation simulations

� Are suitable suite of input parameters available...?


Concluding Remarks� Geomechanics has a crucial role to play in understanding the containment of a storage complex

� Also important for: understanding the surface/sub-surface deformation, providing input to operational

guidelines, impacts on well integrity

� A workflow has been developed to ensure the geomechanical tasks are aligned with project deliverables at successive phases of the project and the right tools and data are applied at the right time

� Alignment of the geomechanics workflow and MMV planning are key

� The MMV program will provide key constraints to the geomechanical simulations and reduce errors for the

forward predictions

� As part of the workflow, key technical challenges were identified for geomechanics and CCS projects

� Fault Leakage, Thermal Response, Reservoir Stress Path, Reactive Transport Modelling and Rock Properties

� Additional complexity owing to CO2 interaction with mineral phases as a function of time

� Key Technical challenge in the geomechanics modeling in the Goldeneye Project has been associated with the thermal response and fracture propagation

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Thank You.....

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CCS and Geomechanics: A Review of Workflows and Some …€¦ · Geomechanics has a crucial role to play in understanding the containment of a storage complex ... Reservoir Stress