体积压裂是页岩气有效开发的关键技术,其利用水力作用形成水力裂缝,沟通天然裂缝,实现缝网改造,但仍不能改善页岩基块渗透性,导致页岩气井存在改造有效期短、产量递减快等问题.通过分析页岩中有机质和黄铁矿等还原环境产物,测试有机质吸附能力,分析页岩有机质和黄铁矿氧化对气体传输能力的影响,探讨页岩氧化增渗的地质条件和工程可行性.研究结果表明:页岩普遍发育有机质和黄铁矿等易被氧化的还原环境产物;氧化页岩中有机质和黄铁矿可影响页岩气体的传输能力;有机质氧化后易形成有机酸,氧化后溶液pH值可低至3,从而溶蚀方解石等碳酸盐矿物;氧化已用于过热蒸汽钻井、消除滤饼、压裂液破胶、杀菌解堵、热采和增产处理等方面,为在工程应用过程中利用氧化改造页岩气层提供了重要经验.页岩气层氧化改造,可溶蚀有机质、黄铁矿和部分碳酸盐矿物,从而产生溶蚀孔缝,形成高温、高压环境,改变页岩气层的矿物组成、孔隙结构和吸附/解吸等特性,进而达到改造页岩气层的目的.%Stimulated reservoir volume fracturing is the key technology for effective development of shale gas,which uses hydraulic force to create hydraulic fracture and connect natural fracture.But it is not capable of increasing the permeability of shale matrix.As a result,some problems still exist in shale gas wells such as short valid period,fast production decline,etc.The products of reductive environment in shale deposition such as organic matter and pyrite were analyzed and the ad sorption ability of organic matter was measured.The effects of organic matter and pyrite oxidation on gas transmission were discussed,and the geological conditions and engineering feasibility of oxidative stimulation to increase shale permeability were analyzed.Results shows that shales generally have organic matter and pyrite and other reductive contents that can be easily oxidized.Oxidation of organic matter and pyrite in shale can affect shale gas transmission capacity.Organic acid can be generated after organic matter oxidization and its solution pH can be as low as 3 after the oxidization,which can dissolve calcite and other carbonate minerals.Oxidation has been used in superheated steam drilling,elimination of filter cake,fracturing fluid breaking glue,thermal recovery production processing,sterilization,etc.These applications provide important experience to engineering application of oxidative stimulation in shale gas reservoir.By using oxidation to stimulate organic-rich shale reservoir,the organic matter and pyrite and some carbonate minerals can be consumed,which brings about the formation of dissolution pore and seam and high temperature and high pressure environment.This can change the mineral composition,pore structure and adsorption/desorption characteristics of the shale reservoir.Therefore,the goal of reforming shale gas reservoir can be achieved.
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