Compaction is the reduction in pore volume due to a change in reservoir pressure. Subsidence is the change in the surface or mudline profile associated with a reduction in the thickness of the producing formations.

What are the Implications of Compaction and Subsidence?
Compaction/subsidence analyses consider the response of the volume element of a reservoir to the change of fluid mass caused by production. Reservoir depletion can lead to drawdown-induced rock deformation and reservoir compaction. Pressure reduction will also affect the far-field in-situ stresses within the reservoir. Compaction may be a significant drive mechanism.

A thorough understanding of a reservoir's geomechanical character-
istics is necessary to calculate hydrocarbon in-place, to estimate ultimate recovery under a compaction drive, to foresee water influx, and to evaluate the potential for surface subsidence. Developing this comprehension early in the development of a reservoir can enable a producer to optimize and manage production.

How Should Realistic Compaction Tables be Generated for your Simulator?
Evaluate/interpret previous geomechanical tests to assess their validity, to extract required data for reservoir simulation and engineering evaluations.
Generate pore volume compressibilities and relevant rock mechanical and strength properties from logs.
Generate rock compressibility, compaction, and permeability multiplier tables required as input for reservoir simulators and for well integrity evaluation/modeling.
Develop well geomechanical models and carry out stress calculations for cased and cemented wells to estimate the maximum generated loads and deformation of the casing strings.

Casing Stability
A possible consequence of unanticipated compaction can be excessive increases in casing loading - in extreme cases, casing failure and ensuing consequences. These failures have been evidenced by tubular/casing/screen damage, loss of sand control, inability to access downhole locations, and tool sticking. Around the world, casing failure is observed in compacting reservoirs.

With failure above the pay, there is loss of access to the reservoir layer(s). These failures can be caused by fault activation and casing shear above the producing horizon or by an influx of shale down to the reservoir.

Forecast Failure and At-Risk Wells and Completion Design Considerations

ADVANTEK can develop geomechanical models of candidate wells in compacting reservoirs. A well integrity analysis option in COMP@™ calculates deformation and stresses generated by the surrounding rock deformation on the casing for a well with a specified trajectory.

Stresses and deformations (including subsidence contours) are determined. Collapse, burst, ovality, doglegs are evaluated. Meshing and pressure distributions are imported directly from reservoir simulations performed using commercial software. Fault movement can be incorporated.

Contact:
Mr. Karim Zaki
Ph. 713.532.7630
Email: Karim@ADVANTEKInternational.com