硬脆性泥页岩微裂缝封堵可视化模拟试验与评价

为了揭示钻井液对硬脆性泥页岩微裂缝的封堵机理，利用自行研制的可视化微裂缝封堵能力评价仪，采用单一和复合封堵材料，以相同时间内的滤失量和承压能力为标准，并结合观察缝内封堵状况，对7种缝宽的模拟微裂缝进行了封堵效果评价。数据处理分析认为，滤失量与封堵压差不是线性关系；缝宽对应于封堵材料粒径分布曲线上的D50~D58时封堵效果较好；封堵效果不随刚性封堵颗粒质量分数增加而提高；可变形溶胀微粒质量分数为0.5%~0.7%时，封堵效果最好；封堵试验表明，封堵的位置有3种，其中在缝内喉道处形成的封堵层相对较致密，承压能力相对较强。研究表明，硬脆性泥页岩微裂缝封堵模拟试验评价方法是可行的，能够对微裂缝封堵机理进行深化研究。 

Visualization Sealing Simulation Test and Evaluation of Hard Brittle Shale Microfracture

In order to understand the sealing mechanism of microfracture in hard and brittle shale,a series of tests have been conducted using the newly developed visual microfracture sealing evaluation instrument.Many kinds of LCMs had been evaluated in the test,including single and combined LCM.Filter loss and sealing pressure were used as the criterion of sealing capacity.Based on the sealing capacity criterion and visible fracture sealing condition,seven simulated fractures with different apertures were evaluated in this article.The results showed that filter loss and sealing pressure difference did not have a linear relationship. Maximum LCM performance could be achieved when fracture aperture was equal to D50-D58 of the LCMs.Better performance would not be achieved with the increment of rigid LCM concentration.The optimum mass fraction range of deformable sealing particles was 0.5%-0.7%.Three different seal locations had been observed in the fracture,and the best sealing performance was achieved when the seal formed in the middle of the fracture.The research results showed that the hard and brittle shale microfracture sealing simulation method was feasible,and it was useful to the further study of the sealing mechanism of microfracture.