STUDY ON FORMATION SEEPAGE BEHAVIOR AND MECHANISM BASED ON CT SCANNING FOR ORDOVICIAN CARBONATE ROCKS OF TARIM BASIN, CHINA

Carbonate reservoirs are one of the main storage spaces for oil and gas resources. It plays an important role in oil and gas exploration and the study of reservoir seepage characteristics is of great significance for improving oil and gas production. For carbonate formation, the connectivity and physical properties are poor. Early researchers have not provided enough study on such formation, especially on the seepage laws and capillary pressure variation. Based on the Ordovician carbonate reservoir samples in the Tarim Basin, the permeability experiments and CT scan experiments were carried out. The microscopic pore structure, permeability and capillary pressure characteristics of carbonate rocks were analyzed. Combined with L-Boltzmann fractal, Hagen-Poiseuille and finite element analysis methods, the microscopic seepage model of carbonate reservoir is established. Results show that these methods can be used in analyzing the seepage behavior of carbonate rocks. The CT scanning permeability is close to the results of conventional physical property analysis. The gas-water relative permeability and capillary pressure calculation are in good agreement with the indoor experimental results. Therefore, considering that the indoor seepage test has the disadvantages of long period, tedious procedures and difficult generalization, the micro seepage theory based on CT scanning can be a good way for the description of seepage phenomena in carbonate reservoirs.