塔里木盆地克深2气藏断层、裂缝、基质“三重介质”渗流及开发机理

Seepage characteristics and development mechanism characterized by faults-fracture-pores "triple medium" in Keshen 2 gas reservoirs,Tarim Basin

克深2气藏属于典型的裂缝性低孔砂岩有水气藏,储层基质物性差,裂缝发育。研究发现,根据传统认识建立的双重介质模型计算的气藏压力传播速度慢、气井见水时间晚,渗流特征与实际存在较大差异。为此,结合当前各种静、动态资料,利用数值试井方法对气藏不稳定试井资料进行了系统分析,在此基础上建立数值模拟机理模型,对该气藏井组干扰试井的压力传播时间、干扰曲线特征以及气井水侵特征都进行了深入研究。结果表明,克深2气藏表现为断层、裂缝、基质"三重介质"的渗流特征,断层是气藏压力传播和水侵的高速通道。边水推进过程中,沿断层的水侵速度明显快于似均质裂缝储层,导致气井快速见水。研究提出的断层、裂缝、基质"三重介质"新渗流模式下的气藏渗流特征与实际情况高度吻合。机理研究表明:保持较低的开采速度,降低边部气井产量,同时优先对中、边部井间有断层的边部见水井进行带水或排水,可有效延缓边水沿断层向气藏中部的侵入速度,提高气藏的最终采收率。

Keshen 2 gas reservoir in Tarim Basin is typical with fractured low-porosity sandstone gas reservoir with edge water. It is mainly characterized by poor petrophysical property in matrix and fracture-developed. The study found that there is great difference between the actual situation and the results obtained from the current double-medium reservoir simulation model based on traditional understanding in aspect of pressure propagating and water-invasion property. Therefore,numerical well test method was used to analyze the pressure transient well testing data,integrated with all kinds of static & performance data. And on this basis,deep analysis with numerical simulation on mechanism model is made on the response time,curve characters of interference well testing and water-invasion property. The result showed that the Keshen 2 gas reservoir is characterized by faultsfracture-matrix "triple medium" flow,and the faults in "triple medium" are the superhighway of reservoir pressure propagating and water-invasion. The non-uniformity in edge water-invasion is very serious and the waterbreakthrough time is much shorter in different structural positions of Keshen 2 gas reservoir,mainly because of its faster migration rate of edge water-invasion in faults than that of fractures. The gas reservoir seepage under the faults-fracture-matrix "triple medium" new seepage mode matches well with the actual pressure propagating and water-invasion property in Keshen 2 gas reservoir. According to the mechanism study results,it is recommended to keep low gas recovery rate and cut the gas production of wells on the edge of reservoir. At the same time,dewatering gas production should be prioritized for watered-out gas wells,where there is fault developed between them and wells in the central part of reservoir. And these are the important measures for controlling edge water incursion rate along the faults and raising the recovery efficiency of gas reservoir.