砂岩气藏岩石孔喉结构及渗流特征

以多孔介质中气水两相渗流理论为基础,选择了四川须家河组气藏岩心,其渗透率在(0.002~70.28)×10-3μm2之间,分别开展了高压压汞、气水相渗以及气藏衰竭开采物理模拟实验研究,从岩石孔喉结构、受力特征以及气水两相渗流特征3方面对比分析了致密与中高渗砂岩气藏特征的差异。采用孔喉类型及数量比例、平均孔喉半径、孔喉中值半径3项参数对不同渗透率砂岩孔喉结构特征进行了精细描述,对比分析了低渗致密与常规及高渗砂岩孔喉结构特征差异;采用排驱压力、沿程阻力量化评价了气、水在不同渗透率砂岩中渗流时的受力情况,对比分析了孔喉结构对致密与常规砂岩产能的影响;建立了气相渗流能力与含水饱和度关系图版,对比分析了含水饱和度大小对不同渗透率岩心气相渗流能力的影响。研究成果将为气藏储层微观建模以及气、水渗流机理研究提供一定的参考依据。

Pore throat structure and flow characteristics of sandstone reservoirs

Mercury injection testing, gas-water relative permeability testing and physical simulation experiments of gas reservoir depletion were carried out with cores from the Xujiahe Formation in the Sichuan Basin (permeability: 0.002-70.28 mD). The differences between tight sand gas reservoirs and high permeability gas reservoirs of the pore structure characteristics, force characteristics and gas-water relative permeability characteristics were analyzed. The approach was as follows: (1) The pore structure characteristics of sandstones with different permeability were described by three parameters: pore throat ratio, average throat radius and median throat radius, and the pore structure characteristic differences between tight sand gas reservoirs and high permeability gas reservoirs were comparatively analyzed. (2) The force situations of gas and water flowing in the sandstones with different permeability were quantitatively evaluated by threshold pressure and frictional drag, and the impacts of pore structure on the capacities of tight sand gas reservoirs and high permeability gas reservoirs were analyzed. (3) The relation diagram of gas relative permeability and water saturation were derived, and the impact of water saturation on the gas relative permeability of cores with different permeability was analyzed. The research results will provide a reference for gas reservoir microcosmic modeling and the study of gas and water percolation mechanism.