致密砂岩气藏气水两相微观数值模拟

Gas-Water Two-Phase Microscopic Numerical Simulation of Tight Sandstone Gas Reservoir

摘要: 针对致密砂岩气藏在开发过程中，存在采收率低，气井产水现象严重的问题。本文从致密砂岩气藏气水两相渗流规律着手，采用CT扫描技术识别二维裂缝，并利用FLUENT数值模拟软件，模拟不同压差下致密砂岩气藏的气水两相渗流规律。结果表明：残余气分布主要分布在不连通的裂隙之中，少部分气体分布在连通裂缝之中；增大压差，气水分布变化，采收率略微提高；缝网越发育，采出程度越小，最终采收率提高程度越小。建议在致密砂岩气藏开采的过程中，可以采取前期增大压差，后期降低废弃压力的方式，使得致密砂岩气藏可以获得较大的产能。研究结果对于致密砂岩气藏开发具有一定的指导意义。

Abstract: Aiming at the tight sandstone gas reservoirs in the development process, there are problems of low recovery rate and serious water production phenomena in gas wells. In this paper, we start from the gas-water two-phase seepage law of tight sandstone gas reservoirs, use CT scanning technology to identify two-dimensional fractures and use FLUENT numerical simulation software to simulate the gas-water two-phase seepage law of tight sandstone gas reservoirs under different pressure differences. The results show that: the residual gas distribution is mainly distributed in the disconnected fractures, and a small portion of the gas is distributed in the connected fractures; increasing the pressure difference, the gas-water distribution changes, and the recovery rate is slightly increased; the more the fracture network is developed, the smaller the degree of extraction is, and the smaller the degree of increase in the final recovery rate is. It is suggested that when mining tight sandstone gas reservoirs, the method of increasing the differential pressure in the early stage and decreasing the waste pressure in the later stage can be adopted so that the tight sandstone gas reservoirs can obtain a larger production capacity. The results of the study have a certain guiding significance for the development of tight sandstone gas reservoirs.