Progress of theories and methods for prediction and detection of pore pressure in carbonate rock

Carbonate rock is a key exploration field in deep and ultra-deep reservoirs, and its pore pressure prediction and detection is a key restricting factor of well control safety. However, due to the complex diagenesis, limestone and dolomite have quite different characteristics, as a result of which the prediction and detection of pore pressure in carbonate rocks has become a world-class problem. To make clear the difficulties, find ideas and point out the direction of scientifically solving this difficult problem, this paper systematically summarizes the characteristics of carbonate rocks, the formation mechanism of pore pressure and the corresponding four types of prediction and detection methods, which are proposed as follows:(1)the composition and structure of carbonate rock are the main controlling factors affecting the physical properties, fluid composition and content, thus affecting its chemical, mechanical and acoustic properties; (2)in deep and ultra-deep reservoirs, the porosity of carbonate rock no longer decreases as the depth increases, indicating that no compaction occurs, and relevant theories and methods are not suitable for the research of carbonate formation; (3)due to the fact that the formation mechanism and evolution process of pore pressure in carbonate rock are complex, and multi-source pressurization mechanism and depressurization mechanism coexist, the calculation model of pore pressure shall avoid the deviation caused by multiple solutions of response characteristics; (4)laboratory core experiment is carried out away from the in-situ environment of burial depth and temperature and pressure field, and the calculation model of pore pressure established on this basis does not take into account all factors, so that it is less applicable. Therefore, the establishment of the abnormal high pressure prediction and detection model shall comprehensively take into account the factors such as formation burial depth, genetic response, temperature and pressure field, rock composition and pore structure. © 2022, Editorial Office of ACTA PETROLEI SINICA. All right reserved.