فهرست مطالب شیرین سامانی

Diagenetic processes in carbonate rocks can be considered as one of the most important factors influencing the inherent characteristics of this type of reservoir on a small as well as large scale. Considering the importance of knowing the mechanical characteristics of reservoir rocks in geomechanical modeling and its application in the exploitation and development of hydrocarbon fields, it is necessary to find out how lithological characteristics affect its rock mechanical behavior. In this study, the impact of two diagenetic processes (Dolomitization and Anhydrite cement) on the physical and mechanical characteristics (such as Uniaxial Compressive Strength, Young’s modulus, Cohesion, and Internal friction angle) of carbonate reservoirs of the Kangan Formation, are addressed. The evaluations have been done in two phases: i.e., lithological studies and rock mechanical tests. The results show that changes in mechanical properties are strongly influenced by diagenetic processes. The two main influential features on mechanical characteristics are dolomitization and anhydrite cementation, which strongly affect porosity, dominant pore type, and mineralogy. The results show that dolomitization in the studied samples has caused an increase in porosity and a decrease in strength and elasticity. While the presence of anhydrite has caused an improvement in the resistance characteristics with an opposite effect.

Elastic properties (Young's modulus and Poisson's ratio) are considered to represent important parameters in geomechanical investigations of reservoirs and hydrocarbon fields. These parameters can be calculated using common geomechanical tests in the laboratory. However, due to the lack of access to suitable samples, laboratory equipment and high costs, in many cases, empirical equations, statistical and mathematical methods have been used to estimate these characteristics. We present a Digital Rock Simulation (DRS) approach using high-resolution CT-images to estimate Young's Modulus and Poisson's ratio of carbonate samples following a non-destructive approach. In the numerical simulations we use a voxel model of reconstructed 3D geometry that is evaluated using Finite Element Method (FEM). We extract Representative Volume Elements (REV) of Kangan carbonates with different porosity and mineralogy. In laboratory experiments, we quantified the modulus based on Axial Stress-Axial Strain Curve that was obtained from Triaxial Compression Tests. Finally, we compare the simulation results and laboratory measurements. Our analysis shows that obtained Young's Modulus of modeling are between 4.3% and 18.9% higher than compared to the results of laboratory tests. The highest error is related to the samples with the more porous, which are mainly dolomite. The assumptions about solid fraction properties regarding to mineralogy differences remains challenging