Fault Seal Analysis

Fault-seal behavior as part of the reservoir development strategy

Faults can be a transmitter of, or a barrier to, fluid flow and pressure communication. When field observations of long-range correlations in well rates do not correspond to expected values based on fluid flow through compact rock formations, reservoir-scale mechanical responses involving faults must be considered.

The rock properties and stresses that develop within fault zones affect a fault’s ability to seal. These properties are affected by many factors, such as the local facies, reservoir fluid types and saturations, pressure differentials across faults, and fault zone architectures. Successful reservoir development strategies must incorporate these aspects to more accurately predict the fault-seal risk.

Modern methods to predict fault-seal behavior

Under a critical stress state, a small change of the effective stress caused by fluid-pressure changes in the reservoir is likely to trigger field-wide hydromechanical reactions, irrespective of whether the change was at local or reservoir scale. Such events can create new faults and reactivate existing ones. Fractures may propagate, potentially changing the reservoir permeability characteristics. These dynamic relationships can be included in the modeling process, based on an initial field wide mechanical earth model that incorporates fault geometries that have been extracted using 3D seismic data analysis, such as Petrel Automated Structural Interpretation.

Dynamic modeling is carried out using the VISAGE, ECLIPSE, and Petrel software packages. Predictions integrate data from a variety of sources—including 3D surface seismic, well logging, core data, and well test data, and can be calibrated with monitoring data such as 4D seismic, microseismic, repeat well logging, subsidence measurements, and wellbore stability events.

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Geomechanics fault seal
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