海相页岩压裂液低返排率成因

发布时间：2018-01-15 21:38

本文关键词：海相页岩压裂液低返排率成因　出处：《天然气工业》2017年07期 　论文类型：期刊论文

【摘要】：为了研究压裂液与页岩作用以及滞留机理,以中国南方海相页岩昭通、长宁和威远区块的岩心为样品,从吸附、膨胀、溶出孔、溶出液矿化度及离子组成等实验研究入手,揭示水在页岩中的赋存状态及高矿化度来源,模拟计算了水的滞留及矿化度增加机理。扫描电镜显示页岩中含有黏土矿物质形成的大量微裂缝,超声浸泡页岩矿物溶出率介于0.5%~0.7%,离子组成与地层水一致,取样岩心黏土矿物含量介于18%~20%,主要为绿泥石、伊利石和少量伊/蒙混层,没有蒙脱石(SS)层,XRD及红外光谱验证压裂液不会进入黏土矿物层间,不会引起页岩膨胀,压裂液滞留主要为压裂新形成的页岩微裂缝表面吸附作用的结果,吸附饱和速度与孔径成正比,为逐步渗透。结论认为,压裂液对页岩的逐级萃取及纳米缝隙对离子排斥是返排后期矿化度急剧增加的主要原因,气藏形成时甲烷携液作用也是可能的原因。结合实验及现场数据,分析了9口井压裂液返排率与产气量数据,结果表明相同区块总体趋势为返排率越低,微裂缝越发达、体积改造效果越好、产气量越大。
[Abstract]:In order to study the interaction between fracturing fluid and shale and retention mechanism, the cores of marine shale Zhaotong, Changning and Weiyuan blocks in southern China were taken as samples from adsorption, expansion and dissolution pore. In order to reveal the occurrence of water in shale and the source of high salinity, the salinity and ion composition of dissolution solution were studied. The mechanism of water retention and salinity increase was simulated and calculated. SEM showed that there were a large number of micro-cracks formed by clay minerals in shale, and the dissolution rate of shale minerals in ultrasonic immersion was between 0.5% and 0.7%. The composition of ions is consistent with that of formation water, and the content of clay in the core is between 18% and 20%, mainly chlorite, Illite and a small amount of Illite / montmorillonite layer without montmorillonite / montmorillonite (SS) layer. XRD and infrared spectra verify that the fracturing fluid will not enter the clay mineral interlayer and will not cause shale expansion. The main result of the fracturing fluid retention is the adsorption on the surface of the new fracturing shale microfracture. The adsorption saturation velocity is proportional to pore size and is a gradual permeation. Conclusion it is concluded that the gradual extraction of shale by fracturing fluid and the exclusion of ions by nanometer gap are the main reasons for the sharp increase of salinity in the late stage of reflux. Combined with experiments and field data, the data of fracturing fluid recovery and gas production in 9 wells are analyzed. The results show that the general trend of the same block is the lower the return rate. The more developed the microcracks, the better the volume transformation effect and the greater the gas production.
【作者单位】：中国石油勘探开发研究院;天津科技大学;
【基金】：国家重点基础研究发展计划(973计划)项目“中国南方海相页岩气高效开发的基础研究”(编号:2013CB228000)
【分类号】：TE357.12
【正文快照】： 压裂为页岩体积改造的常规方法,但返排率不高,一般介于10%~60%[1-3],大量液体滞留在储层内,页岩为致密储层,均质性差,陈志鹏等[4]对昭通龙马溪组页岩进行分析后,认为该区域形成储层超压的原因是富含有机质页岩生烃增压、深埋和盆地构造挤压、剥蚀卸载以及致密的封盖围岩。蒲泊

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