Pore Collapse in Weakly Cemented and Porous Rocks

Withdrawal of fluids from hydrocarbon reservoirs results in a decrease in pore pressure which in turn leads to an increase in effective stress on rock matrix. Such a situation may lead to the occurrence of pore collapse in reservoirs having weakly cemented, porous rocks. It is considered to be a potential problem in several producing reservoirs. Numerical simulation of a compacting reservoir due to pore collapse requires an appropriate constitutive model. Consequently, a constitutive model based on the concept of elasto-plasticity using isotropic hardening is developed to predict pre and post-pore collapse behavior of reservoir rocks. An experimental study is carried out on a high-porosity rock susceptible to pore collapse for different stress paths. The developed constitutive model is tested with respect to two different materials exhibiting such behavior. Parameters for the model are evaluated based on the experimental results, highlighting the procedure involved. Further, the data is used to demonstrate the strengths and the weaknesses of the constitutive model. Experimental data for the second material is obtained from literature. Satisfactory agreement is achieved between experimental data and model predictions.