致密砂岩气藏水锁损害及解水锁实验研究

塔里木油田B区块目标层段为白垩系巴什基奇克组，井深大于6000m，储层岩性致密，孔隙度分布在1.0%~9.4%，渗透率分布在0.011×10-3~8.56×10-3μm2，孔隙度与渗透率关系较差，储层总体孔隙发育程度低，渗透率差，非均质性严重，微裂缝发育，毛细管力高，黏矿物含量高，在完井及压裂过程中极易受到水锁损害。基于该区块地质特征分析潜在水锁损害及水锁空间，发现毛细管水近乎占据了储集空间的一半，气相渗流极其困难。使用DSRT-II型低渗敏感性评价试验仪，应用岩心流动实验从宏观角度分析水锁损害，采用核磁共振T2谱测试，从微观角度定量分析水锁损害程度，结果表明该区块水锁损害使渗透率降低99%，液锁量90%以上，主要分布在微孔隙0.01~250nm中，水锁损害严重。结合水锁损害机理与室内实验研究，优选解水锁剂，借助毛细管自吸实验、核磁共振测试、渗透率损害率评价，进行解水锁实验研究。结果表明，优选的解水锁剂SATRO-1和HUL能有效降低毛细管力，减小自吸侵入深度，并有助于小孔喉液体返排。 

Study on Water Block in Tight Sandstone Gas Reservoirs and Solutions Thereof

The target zone of the block B in Tarim Basin is the Cretaceous Bashijiqike Formation. The depth of the wells drilled is greater than 6,000 m, and the reservoir rocks are tight, with porosity ranging from 1.0%to 9.4%, and permeability from 0.011×10-3 to 8.56×10-3μm2. The porosity has poor relationship with permeability. The highly heterogeneous reservoir rocks have poorly developed pores, low permeability, developed fractures, high capillary forces, high clay contents, and are very easy to be affected by water blocking during well completion and fracturing. Analyses of water blocking based on the geological features of the reservoir rocks in this area indicate that the capillary water accounts for almost half of the volume of the pores, leading to highly difficult gas flow in the porous media. Using the Model SRT-II low permeability sensitivity tester, formation damage by water blocking is macroscopically analyzed through core flow experiment. Using NMR transverse relaxation time spectrum, formation damage by water blocking is microscopically analyzed. The analyses show that water blocking caused the permeability of the reservoir rocks to be reduced by 99%, and more than 90%of the water blocked in this area, mainly in the 0.01-250 nm pores. Based on the research, water blocking remover SATR0-1 and HUL were chosen and their performance studied through capillary imbibition, NMR examination, and permeability experiments. It was concluded that SATR0-1 and HUL can effectively reduce capillary forces and invasion depths by imbibition, and are helpful to liquid flowback through micro pore throats.