UPVC Test Design, Interpretation, and Simulation for Compaction and Subsidence

In the field which exhibit relatively high rate of compaction and subsidence, rock mechanics laboratory testing is crucial to explain the rock deformation during production period. In the studied field, the conventional core is planned for different rock mechanics testing, and uniaxial pore volume compressibility (UPVC) tests were allocated for understanding behavior of rock compressibility. With limited core availability, 8 samples were planned for the test. There are several failure criteria that can be used to describe reservoir compaction in the carbonate reservoir, critical state is one of them. Critical state failure criterion was used to represent the behavior of rock at field scale geomechanical modelling as most of input parameters can be derived from the laboratory tests. With limited knowledge of how UPVC test should be designed to provide the interpretation for collapse pressure, hardening parameter, the first version of UPVC stress path cannot reveal the on-set of pore collapse during the core depletion. The UPVC test was then re-designed, and the results show the clear evidence of pore collapse behavior which varies with porosity. Due to limited sample, the collapse pressure can be interpreted only in a limited range of porosity. With uncertainty of the laboratory measurement, the relationship between hardening parameters and the reservoir property e.g., porosity cannot be derived. With all UPVC test results, the collapse pressure as a function of porosity can be derived. To ensure that the interpreted parameters for critical state criterion can mimic the stress-strain relationship during UPVC test, finite element modelling using “single element simulation” was used for the model validation. This simulation will simulate the rock deformation during laboratory test at core scale, both in elastic regime and yielding. With proper failure criterion and provided input parameters, the single element simulation can mimic the actual stress strain relationship during laboratory test and provide the confidence of using those input parameters and criterion later in the field scale geomechanical modelling and simulation.