东胜气田致密砂岩储层渗流机理

致密砂岩气藏渗流阻力大,废弃压力高,采收率低,含水饱和度影响显著,明确致密砂岩储层气体的渗流机理对于气藏的有效开发具有重要意义。选取东胜气田致密砂岩储层样品100余块,开展了孔渗测试及其相互关系与分布特征分析；进行了致密砂岩储层在不同含水饱和度下的气体渗流特征实验,计算了单相气体及不同含水饱和度下气体渗流的滑脱因子；测试了样品在不同驱替压力下的气水两相相对渗透率曲线。实验研究结果表明：东胜气田致密砂岩储层覆压渗透率约为常压下测得的标准渗透率的1/10,且普遍低于0.1mD,孔隙度偏低；滑脱效应受渗透率、孔隙压力、含水饱和度影响明显；干岩心气体临界流态特征明显,小于0.1mD岩样渗流特征曲线为线性,大于0.1mD岩样非线性特征明显；含水饱和度对于渗流特征曲线影响显著,随着含水饱和度增加,气体渗流由气态渗流过渡到液态渗流,气相渗流滑脱效应逐渐变弱；驱替压差对残余水饱和度影响大,控制气藏生产压差,防止大压差驱动储层水,导致气井大量产水。渗流机理研究对于东胜致密砂岩含水气藏的合理、有效开发具有重要的基础理论支撑作用。

Study on Seepage Mechanism of Tight Sandstone Reservoir in Dongsheng Gas FieldWU Jianbiao

Tight sandstone gas reservoir has high seepage resistance, high abandonment pressure, low recovery rate and significant influence of water saturation. It is of great significance to clarify the gas percolation mechanism of tight sandstone reservoir for effective gas reservoir development. More than 100 tight sandstone reservoir samples from Dongsheng Gas Field were selected to carry out pore permeability tests and their relationship and distribution characteristics were analyzed. The gas seepage characteristics of tight sandstone reservoir under different water saturation are tested, and the slippage factors of gas seepage under single-phase gas and different water saturation are calculated. The gas-water relative permeability curves of the samples under different displacement pressures were tested. The experimental results show that the overburden permeability of tight sandstone reservoir in Dongsheng Gas Field is about 1/10 of the standard permeability measured under atmospheric pressure, and generally lower than 0.1mD. The porosity of tight sandstone reservoir in Dongsheng Gas Field is low. The slippage effect is obviously affected by permeability, pore pressure and water saturation. The critical flow state of dry core gas is obvious, and the seepage characteristic curve of rock sample which permeability is less than 0.1mD is linear, while that of rock sample which permeability is greater than 0.1mD is nonlinear. Water saturation has a significant influence on the seepage characteristic. With the increase of water saturation, gas seepage transitions from gaseous seepage to liquid seepage, and the slippage effect of gas phase seepage gradually weakens. Differential displacement pressure has a great influence on residual water saturation, so it can control the differential production pressure of gas reservoir to prevent the massive water production in gas well caused by the drive of reservoir water by large pressure difference. The study of seepage mechanism has important theoretical support for the rational and effective development of tight sandstone gas reservoir in Dongsheng Gas Field.