Analysis of deformation and induced stress fields in wells during water flooding operations of carbonate reservoirs

In this study, deformation curves and induced stress changes around injection wells, before and after the water flooding process, have been investigated in the Asmari carbonate reservoirs of the Ahvaz oil field, located in the southwest of Iran. To achieve this, two types of tests were conducted on six carbonate core samples from the reservoir: (1) flooding device test and (2) triaxial compressive test. The results of these experiments revealed that Mohr’s circles, deformation curves, and induced stresses around the injection well were affected by the water flooding process. By utilizing flooding devices and triaxial testing, as well as intergating their results, changes in parameters, geomechanical coefficients, and Mohr’s circles were analyzed for all six carbonate core samples. The analysis was based on the Hooke-Brown and Mohr-Coulomb failure criteria under both natural production conditions and during production. In the current study, a novel and sequential approach was employed to integrate data collected before and after the water flooding process, including full set log data, results from water flooding and triaxial tests, and the experimental data from water flooding operations in the carbonate reservoir of the Ahvaz field. Using MATLAB software, the induced stresses around the injection well were simulated and analyzed through three-dimensional diagrams. The findings demonstrated that after water flooding and the associated pressure increase, the induced stresses around the injection well—namely vertical, radial, and tangential stresses—undergo significant alterations. Before the water flooding process, the maximum stresses for the three carbonate core samples were approximately 68, 91, and 107 MPa, respectively. Following the water flooding process, these values increased to approximately 94, 118, and 142 MPa, respectively. The results reveal that, following the water flooding process, the minimum stress remains unchanged while the maximum stress increases. Consequentially, Mohr’s circle becomes larger compared to the initial state.