钻井完井液损害对致密砂岩应力敏感性的强化作用

致密砂岩储层在钻井完井作业过程中易遭受应力敏感，许多学者对基质岩样或裂缝岩样进行大量实验研究工作，然而对钻井完井液损害裂缝性致密砂岩储层后的应力敏感性研究较少。文章以四川盆地某典型致密砂岩气藏为研究对象，选取工作液侵入损害后的裂缝岩样和未损害裂缝岩样，再利用SCMS－I型高温高压岩心多参数测量系统对两类岩样进行加压、降压应力敏感实验。结果表明，常规裂缝岩样应力敏感系数平均为0.43，应力敏感程度为中等；工作液损害裂缝岩样应力敏感系数平均为0.66，应力敏感程度为中偏强。建立岩样受力模型，分析认为，随有效应力增加，侵入裂缝的固相颗粒在裂缝中充当胶结物，极大地降低了裂缝的渗流能力，导致储层产能降低。

Drill-in Fluid Damage will Strenghthen the Stress Sensitivity of Tight Sands

The stress sensitivity is an important reason to cause formation damage in tight sands reservoir. Many scholars have studied the stress sensitivity in matrix rocks and fractured rocks, few people studied the stress sensitivity of fractured tight sands after damaged by the drilling and completion fluids. By means of contrast experimentation, the core samples with the working fluid intrusion and the regular undamaged core samples are selected, and then the SCM-I HPHT core test system is used to appraise stress sensitivity by increasing and reducing the stress. The result is that the stress sensitivity of the core samples already damaged by working fluid is obviously strengthened. For undamaged core samples, the average stress sensitivity is 0.43, the stress sensitivity is of a medium level; for the core samples with the working fluid intrusion, the average stress sensitivity is 0.66, the stress sensitivity is from medium to serious level. From the stress models of the core samples, it shows solid particles invaded into the fracture will act as cementing matter when the stress increases,which can reduce the fracture percolation ability and result in production decrease.