富有机质页岩增产改造氧化液浸泡离子溶出行为

页岩储层富含有机质、黄铁矿等还原性组分，因而氧化溶蚀致裂是极具潜力成为一种新的页岩油气层增产改造技术。以往研究侧重于页岩氧化后孔隙结构及传质能力的变化，但对页岩氧化过程水溶液性质变化关注不多，而水溶液性质又与压裂液返排、黏土水化作用、水相圈闭损害缓解等密切相关。选取四川盆地龙马溪组富有机质页岩粉体样品，实验测试了页岩粉体样品与蒸馏水、不同浓度氧化液浸泡过程水溶液离子组成、pH、电导率和浊度等参数，精细描述了页岩氧化反应过程。实验结果表明，页岩氧化液浸泡时溶液中Fe³⁺、Ca^2+、Mg²⁺等离子的浓度大幅度增加、pH降低、电导率和浊度增加。分析认为，氧化液选择性溶解页岩中黄铁矿、有机质等还原性组分和(铁)白云石、方解石等碳酸盐矿物，释放出离子；或将矿物集合体分散成粒径更小的微粒，从微观层面上“破碎”页岩中部分矿物，形成溶蚀孔和微裂缝，有利于提高页岩渗透率；宜合理调控入井氧化液浓度和氧化处理时间，优化设计处理工艺；页岩氧化改造后的返排液处理，可沿用现行的页岩压裂返排液处理方法和工艺。

Ionic dissolution behaviors of organic shale soaked in oxidizing liquid for reservoirs stimulation

Shale reservoirs are rich in reductive contents such as organic matter and pyrite,thus corrosion and fracturing shale by oxidation can have great potential to be a new technology for shale reservoir stimulation.Previous studies focused more on the changes in pore structure and multi-scale seepage capacity of the shale after oxidation,and not much attention was paid to the changes in the properties of aqueous solution in the process of shale oxidation.However,the properties of aqueous solution have important influence on the returnedfracturing fluid,clay hydration,and relieving aqueous phase trapping damage.The organic matter-rich shale powder samples of Longmaxi Formation in Sichuan Basin were selected to conduct the experiment of immersion in oxidizing liquid with different concentrations and distilled water respectively,and the parameters of cationic composition,pH,Ec,and turbidity of aqueous solution were tested,and the oxidation process of shale was described in detail.In oxidation environment,the dissolved amount of Fe³⁺,Ca²⁺ and Mg^2+ions in the liquid increases sharply,the pH of the liquid is low,the Ec and turbidity increase.This paper draws the conclusion that the oxidation selectively dissolves the reductive contents such as pyrite,organic matters and the carbonate minerals such as (ankerite) dolomite and calcite in the shale,and releases ion,or disperses mineral aggregates into the size-smaller particles.Some of the shale minerals are “broken” at the microcosmic level,and dissolved pores and micro-cracks are formed,which will help improve the permeability of shale matrix.It is advisable to regulate and control the concentration of oxidizing liquid and the treatment time of oxidation,and optimum and design the treatment process.The flow-back fluid in oxidative stimulation can be dealt with the existing treating methods and technics of shale fracturing flow-back fluid.