致密砂岩气藏负压差水相圈闭损害过程模拟  

Experimental simulation of water phase trapping damage in tight sandstone gas reservoirs under conditions of negative pressure difference

作　　者：游利军[1] 田键[1] 王娟娟[2] 康毅力[1] 程秋菊[2] 乔国安[2] 

机构地区：[1]西南石油大学油气藏地质及开发工程国家重点实验室,四川成都610500 [2]中国石化华北油气分公司石油工程技术研究院,河南郑州450006

出　　处：《油气地质与采收率》2016年第2期87-92,共6页Petroleum Geology and Recovery Efficiency

基　　金：国家"973"计划"深井复杂地层漏失与井壁失稳机理及预测"(2010CB226705);国家科技重大专项"页岩气层工程作业适应性评价及保护对策研究"(2011ZX05018-005)

摘　　要：致密砂岩气藏具有低孔低渗透、高毛管压力、天然裂缝发育和超低含水饱和度等工程地质特征,存在明显的毛管自吸现象,即使在负压差条件下,毛管压力也会使水相逆流自吸进入储层,引起水相圈闭损害。选用鄂尔多斯盆地典型致密砂岩气藏相对低渗透(渗透率小于0.2×10^(-3)μm^2)、相对中渗透(渗透率为0.2×10^(-3)~0.5×10^(-3)μm^2)和相对高渗透(大于0.5×10^(-3)μm^2)的3类致密砂岩岩样,开展水相毛管逆流自吸实验和气驱水返排实验,模拟负压差条件下水相圈闭损害发生过程,探讨水相逆流自吸对气相渗透率的影响,评价负压差条件下水相圈闭损害程度。实验结果表明:负压差下水相逆流自吸对气相渗透率的损害呈现由岩样物性控制的阶跃式变化特征。同一负压差下,3类岩样气相渗透率损害率为26.5%~34.9%,平均损害率为29.8%;负压差越小,对毛管压力的克服作用越弱,毛管自吸越明显,水相进入岩心位置越深,引起的水相圈闭损害越严重。因此,在欠平衡钻井、完井和开发过程中,确定生产压差时应综合考虑安全作业、储层水相返排等因素。With some engineering geology features of low-porosity and permeability,high capillary pressure,developed natural cracks and ultra-low water saturation,the tight sandstone gas reservoirs have strong imbibition phenomenon,which could lead to water phase trapping damage due to countercurrent capillary imbibition of water in reservoir even under conditions of negative pressure difference. Some typical tight sandstone core samples from Ordos basin with different permeabilities of less than 0.2×10^(-3)μm^2 ,between 0.2×10-3and 0.5×10^(-3)μm^2 and higher than 0.5×10^(-3)μm^2 were selected to evaluate the counter current capillary imbibition and water flow-back during gas driving. The process of water phase trapping damage was simulated under negative pressure difference and the effect of countercurrent water imbibition on the gas permeability was discussed to know the damage degree. The results indicate that the decrease of gas permeability caused by the countercurrent imbibition under the negative pressure difference is more likely to have some characteristics of step change controlled by the physical properties of cores. The permeability damage ranges from 26.5% to 34.9% with the average of 29.8% under the same negative pressure difference. The lower the negative pressure difference is,the stronger the countercurrent imbibition is,which leads to deep entrance of water and more serious water phase trapping damage. So,safe opera-tion,water flow-back in reservoir and other factors should be considered when the drawdown pressure is fixed during underbalanced drilling and completion and development.

关 键 词：致密砂岩气藏 负压差 逆流自吸 返排 水相圈闭 

分 类 号：TE353.3[石油与天然气工程—油气田开发工程]