东胜气田致密砂岩储层渗流机理

Seepage Mechanism of Tight Sandstone Reservoir in Dongsheng Gas Field

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0.1 mD,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0.1 mD岩样渗流特征曲线为线性,大于0.1 mD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。

The gas seepage resistance of tight sandstone reservoirs is high, the abandoned pressure is high, the recovery rate is low, and the water saturation has significant influence. It is important to clarify the gas seepage mechanism of tight sandstone reservoirs for the effective development. More than 100 samples of tight sandstone reservoir in Dongsheng gas field were selected, and the pore permeation test and its interrelationship and distribution characteristics were carried out. Experiments on gas seepage characteristics of dense sandstone reservoirs at different water saturation levels were carried out. The slip factors of single-phase gas and gas seepage at different water saturation were calculated. The relative permeability curves of gas and water phases of the samples under different drive pressures were tested. The experimental results show that the overburden permeability of the tight sandstone reservoir in Dongsheng field is about 1/10 of the standard permeability measured at normal pressure, and is generally lower than 0.1 mD, with low porosity. The slip effect is significantly affected by permeability, pore pressure and water saturation. The gas critical flow characteristics of dry cores are obvious, the seepage characteristic curve of rock samples less than 0.1 mD is linear, and the non-linear characteristics of rock samples larger than 0.1 mD are obvious. The water saturation has a significant influence on the seepage characteristic curve, as the water saturation increases, the gas seepage transitions from gaseous to liquid seepage, and the gas phase seepage slip effect gradually becomes weaker. The drive pressure difference has a great influence on the residual water saturation, control the gas reservoir production The pressure differential has a strong influence on the residual water saturation, and controls the reservoir production pressure differential to prevent large pressure differentials from driving reservoir water and leading to large water production from gas wells. The study of seepage mechanism is an important basic theoretical support for the rational and effective development of water-bearing gas reservoirs in the Dongsheng tight sandstone.