川西南筇竹寺组页岩盐敏性实验评价新方法

孔喉致密、黏土矿物含量高使得页岩气层具有严重的潜在盐敏性损害特征。用现行行业标准(SY/T 5358—2010)评价页岩盐敏性时,存在对实验设备要求高、测试流程长、实验误差大等问题。提出气测渗透率法评价页岩盐敏性,通过比较岩心经液体污染前后气体渗透率变化来反映盐敏性。该方法不需计算岩心出口端流量,从而解决了页岩液体渗透率过低而引起的测试周期长、实验误差大等常规评价问题。此外,行业标准法实验采用液体为实验介质,而气体渗透能力是影响页岩气层产能的主要参数,因此气测渗透率法更符合气层生产实际。盐敏性实验研究结果表明,该储层盐敏指数为74.51~82.80,盐敏性强,施工过程中应尽量避免或者减少碱敏损害。同时该实验方法为后续以气测渗透率为中心的流体敏感性实验评价打下了基础。

A new experimental method to evaluate salt sensitivity of shale from Qiongzhusi formation

Dense pore throats and high content of clay minerals cause serious potential sensitivity damage to shale gas reservoirs. However, during industry standard method experiments, big errors appear since it is hard to measure the liquid flow for the ultra-low liquid permeability and ultra-slow movement of liquid in shale cores. A new way based on gas permeability method is raised in this article to evaluate liquid sensitivity of shale. It is not necessary to measure fluid flow rate at outlet of the core holder, which reduce test period and experimental error caused by ultra-low fluid permeability. Besides, liquid is adopted during industrial standard tests, while gas method conforms more to the fact. Experimental results indicate that salt sensitivity of shales from Qiongzhusi formation is strong, and the experimental method lays foundation to evaluate other fluid sensitivity on the basis of gas permeability.