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页岩气藏基质储渗空间为纳米尺度,超低含水饱和度,高黏土矿物含量,发育微裂缝,需经压裂改造投产,气体产出是一个多尺度、多种传质过程,但压裂液易产生滞留,影响气体产出。页岩渗透率为纳达西级,难以利用测量损害前后渗透率的传统方法评价页岩气层损害。采用四川露头页岩岩样和4种滑溜水压裂液体系,利用压力衰减法,结合水相渗吸实验和气驱水返排实验,评价了压裂液滤液对岩心尺度的损害程度,分析了页岩气藏工作液损害评价的指标,认为传统渗透能力恢复率或渗透率恢复率不能作为页岩气层损害评价的唯一指标。基于评价结果,结合目前部分压裂液返排率低的气井产量反而比较高的非常规现象分析,指出页岩压裂液诱发水相圈闭损害是一个动态过程,具有尺度性,在评价过程还要考虑滞留压裂液对气体传递的积极作用,压裂液作用及返排制度是未来5~10年值得研究的重点问题。
The matrix storage space for shale gas reservoirs is of nanoscale, ultra-low water saturation, high clay mineral content and micro-fractures, which need to be reformed and put into production. Gas production is a multi-scale and multi-mass transfer process. However, Fissures easy to produce retention, affecting the gas output. Shale permeability is Nadaxi grade, making it difficult to assess shale gas damage using traditional methods of measuring permeability before and after damage. Using outcrop shale rock samples and four kinds of slippery water fracturing fluid system in Sichuan, the damage degree of fracturing fluid filtrate on the core scale was evaluated by pressure decay method, combined with water phase imbibition experiment and gas flooding back flow experiment. Shale gas reservoir working fluid damage assessment indicators, that the conventional permeability recovery rate or permeability recovery rate can not be used as the only indicator of shale gas damage assessment. Based on the evaluation results and the unconventional phenomenon that the fracturing fluid has a low backflow rate at the current rate, the yield of gas wells is relatively high. It is pointed out that the trapping fluid induced by shale fracturing fluid is a dynamic process with scale. During the evaluation process But also consider the active role of the fracturing fluid on the gas transmission. The fracturing fluid and the return system are the key issues to be studied in the next 5 to 10 years.