高含水低渗致密砂岩气藏储量动用动态物理模拟

Physical Simulation of Reserve Producing State in Water-bearing Tight Sandstone Gas Reservoir

气藏剩余压力分布能够直接反映其储量动用情况,采用长岩心多点测压实验装置,选择渗透率分布区间分别为(1.38~1.71)×10^(-3)μm^2、(0.41~0.73)×10^(-3)μm^2、(0.049~0.084)×10^(-3)μm^2的多块砂岩岩心组合形成长度超过50cm的3组长岩心,模拟含水砂岩气藏衰竭开采。实验过程中实时记录气藏边界至气井不同位置处压力剖面变化,研究含水气藏储量动用特征。研究表明:致密砂岩储层产气特征、压力剖面形态、压降过程、废弃时剩余压力分布均与渗透率较高的储层(Ⅰ类)差异显著,明显受渗透率和含水饱和度控制。含水相同(约35%),生产至废弃条件时,Ⅰ类储层的压力剖面整体几乎降为0,而致密砂岩、剩余压力仍维持在原始压力的50%以上,且压力梯度大,表明含水气藏,渗透率越低储量动用越困难,动用均衡性越差;考虑含水,随含水饱和度增加,Ⅰ类储层压力剖面形态及下降过程变化不大;渗透率更低的储层(Ⅱ类)尤其是致密储层(Ⅲ类),其压力剖面形态变化极为显著,含水较高时,压力难以向外波及,储量难以有效动用,且非均衡性极强。

Abstract：Using long core multipoint press measurement experimental facility,three-group long cores were connect- ed by a number of sandstone cores which have permeability of （1.38-1.71） × 10-3 μm2, （0. 41-0.73）×10-3μm2 , （0. 049-0. 084）×10-3μm2 , to simulate the process of depletion-drive in water-bearing sandstone reservoir. Pressure profile from reservoir boundary to gas well was measured and recorded during the experimentation to study the characteristics of reserve utilization. The study shows that, the gas production characteristics, pressure profile shape, pressure drop process, residual pressure distribution of tight sandstone gas reservoir are very different from those of convention gas reservoir, all of which were influenced by permeability and water saturation more obviously. For those with the same water saturation （about 35%）,when the production is carried out until abandonment pressure, the pressure profile of convention gas reservoir will drop to zero,while residual pressure of tight gas reservoir still maintains 50% of the initial,and has bigger pressure gradient. The results show that for water-bearing tight sandstone gas reservoir, the lower permeability, the more difficult and less equitability of reserves utilization. Considering water saturation,when water saturation increase, the pressure profile＇s shape and drop process of convention reservoir show little change, but to low-permeability reservoir especially tight reservoir, the pressure profile shape changes remarkably, in high water saturation, pressure drop spread outward difficultly, less effective and equitability of reserve utilization.