致密砂岩气藏气水两相渗流规律影响因素分析

Analysis of Influencing Factors of Gas-Water Two-Phase Seepage Law in Tight Sandstone Gas Reservoir

摘要: 致密砂岩气藏在我国的储量丰富，分布也很广泛，相较于致密砂岩气藏丰富的资源储量，我们对于致密砂岩气藏的开采能力却相当不足。这是由于致密砂岩气藏孔隙细小、喉道狭窄、储层中含水高使得气–水两相的渗流特征十分复杂，影响了致密砂岩气藏的开发效果。本文进行了致密砂岩岩心的室内物理模拟实验，分析了物性、围压、温度和驱替压差对气–水两相渗流的影响，得到的主要结论如下：1) 非稳态气–水相渗实验与其他物理模拟方法相比更加简单，便于操作。2) 岩心的物性差，其束缚水饱和度会相对较大，气相和水相渗流能力相对较差；岩心受到的围压增大，岩心中的束缚水变得更多，两相渗流能力下降；岩心所处环境温度上升，岩心中的束缚水会变少，气相流动能力下降，水相则相反；驱替压差增大，岩心中更多的水被驱出，束缚水减少，两相渗流能力增强。3) 归一化处理后的相渗曲线可用于计算区块的含水率。

Abstract: Tight sandstone gas reservoirs are abundant and widely distributed in China. Compared with the abundant resource reserves of tight sandstone gas reservoirs, our mining capacity for tight sandstone gas reservoirs is quite insufficient. This is because the tight sandstone gas reservoir has small pores, narrow throats, and high water content in the reservoir, which makes the seepage characteristics of the gas-water two-phase very complex, affecting the development effect of the tight sandstone gas reservoir. In this paper, the indoor physical simulation experiment of tight sandstone core is carried out, and the influence of physical properties, confining pressure, temperature and displacement pressure difference on gas-water two-phase seepage is analyzed. The main conclusions are as follows: 1) The unsteady gas-water relative permeability experiment is simpler and easier to operate than other physical simulation methods. 2) The physical properties of the core are poor, the irreducible water saturation will be relatively large, and the gas phase and water phase seepage capacity are relatively poor. The confining pressure of the core increases, the bound water in the core becomes more, and the two-phase seepage capacity decreases. When the ambient temperature of the core rises, the bound water in the core will decrease, the gas phase flow capacity will decrease, and the water phase will be the opposite; as the displacement pressure difference increases, more water in the core is expelled, the bound water is reduced, and the two-phase seepage capacity is enhanced. 3) The normalized relative permeability curve can be used to calculate the water content of the block.