低渗砂岩克氏渗透率影响因素实验研究

室内实验是认识储层渗流规律的有效手段,低渗岩石气体渗流受到滑脱效应的影响。国内外学者在滑脱效应影响因素及受滑脱效应影响的渗透率参数测量方面进行了大量研究,但结论仍存在分歧。以鄂尔多斯盆地苏里格气田低渗砂岩气藏为研究对象,设计了新的岩心含水饱和度的建立方法,通过实验方法研究了含水饱和度、有效应力及二者耦合作用对低渗岩石气体滑脱效应的影响规律。结果表明,不同含水饱和度条件下(低于束缚水饱和度)岩心的气测渗透率与平均压力倒数仍然呈线性正相关关系,含水饱和度越高,滑脱因子越小,滑脱效应越弱;对于干岩样,围压增大气体滑脱效应变强,且滑脱因子随有效应力的增加呈线性增加的趋势,进行岩石应力敏感性实验过程中,若忽略滑脱效应的影响,未对气测渗透率做校正,实验评价结果偏低;含水饱和度比介质变形对气体滑脱效应的影响更强,对于高含水饱和度的低渗岩心,滑脱效应影响微弱,且受有效应力的影响不大。这为低渗砂岩气藏渗流机理研究提供了新思路。

Experimental Study on Factors of Klinkenberg Permeability in Low Permeable Sandstone

Laboratory experiment is an effective means to investigate the fluid flow in reservoirs. Gas flow in low permeability is affected by slippage effect. Many scholars studied the factors of affecting slippage effect and the permeability parameter measurement affected by slippage effect, but differences were still obvious in their studied conclusions. To study the low permeability sandstone gas reservoir in Sulige gas field of Ordos Basin, a new method of establishing core water saturation was designed. A series of experiments were designed to study the influences of water saturation, effective stress, and they coupling on gas slippage effect in low permeability rock. The results show that the relationship of gas log permeability and the reciprocal of the average pressure remains positive linear correlation under different water saturation conditions (less than irreducible water saturation). The slip factor decreases with the water saturation increasing. For dry cores, the gas slippage effect becomes stronger when confining pressure increasing, and the slippage factor increases linearly with effective stress increasing. So, in the stress sensitivity experiment, evaluation of experimental results is much lower if ignoring slippage effect and not correcting the gas log permeability. The influence of water saturation on gas slippage effect is stronger than the media deformation. Slippage effect is weak and is not affected by the effective stress obviously for high water saturation and low permeability core. The study provides a new idea for the mechanism of gas flow in low permeability sandstone reservoir.