致密砂岩气藏水相圈闭损害实验研究及应用

Experiments and Applications of Water Phase Trapping in Tight Gas Sand reservoirs.

致密砂岩气藏已成为当前油气勘探开发的重点,但水相圈闭损害严重影响其勘探开发效益。鄂尔多斯盆地北部塔巴庙致密砂岩气藏具有低孔低渗、低压、高毛管力、高有效应力、低初始含水饱和度、天然裂缝一定程度发育和粘土矿物丰富多样等特征。对塔巴庙致密砂岩气藏地质特征和水相圈闭损害机理的研究表明,致密砂岩气藏潜在水相圈闭损害严重,并通过典型致密砂岩岩样的毛管自吸实验和水相圈闭指数APTi实验评价证实水相圈闭损害的严重性。毛管自吸实验揭示出,物性越好、初始含水饱和度越低的储层更易发生自吸诱发的水相圈闭损害。综合地质特征和实验结果,分析了塔巴庙地区应用屏蔽暂堵钻井完井液防止水相圈闭损害而促使盒2+3段高产气藏及时发现的原因。

Water trap constitutes a hampering barrier and an urgent research topic for effective exploration and exploitation of tight gas sand reservoirs.A series of scientific experiments and field applications were conducted taking Ordos Northern Basin as the entry example for resolving this problem.Ordos Northern Basin reservoir is mainly composed of fracture-developed sandstone with abundant different clay components and is characterized by its low porosity and permeability,low pressure,high capillary pressure,low initial water saturation.The mechanism and characteristics of water trapping in this reservoir was examined with typical sandstone core samples in details by lab experiments on spontaneous water imbibition andby calculations of water trapping index.The results of the experiments showed that the better physical properties and lower initial water saturation may easily result in imbibition-induced damage.Based on the knowledge obtained from these experiments,the reason of the quick and instant discovery of P1x2+3 gas-rich reservoir in Tabamiao region by using bridging techniques was successfully realized.