四川某地页岩气开发中压裂液组分演化及其对地下水的影响

发布时间：2018-11-08 11:40

【摘要】：随着天然气需求增加,页岩气作为一种新型的非常规天然气资源,越来越受到关注。页岩气指赋存于以富含有机质页岩为主的储集岩系中的非常规天然气。我国页岩气开发起步较晚,开发过程中带来的环境影响及污染成因尚缺乏系统的研究。论文在总结前人研究成果的基础上,基于四川某页岩气开采区的实际条件和资料,进行了页岩气开采层水文地球化学模拟研究、返排液对地下水环境影响研究和返排液中典型有机物的淋溶迁移性评价,研究成果如下:(1)页岩气开采层水文地球化学过程模拟结果表明:深部水岩作用矿物溶解由快到慢依次为:碳酸盐矿物(方解石、白云石);长石矿物(钾长石、钠长石);黄铁矿;石英;粘土矿物(伊利石、蒙脱石、绿泥石、高岭石);溶液中的Ca~(2+)、Mg~(2+)、HCO3-、K~+、Fe(t)和Al~(3+)浓度由于矿物的溶解作用而不断增大,使溶液中TDS升高近4倍;不同页岩水岩作用后矿物溶解量与其脆性矿物(石英、长石和碳酸盐矿物之和)含量成正比。(2)高盐度、复杂成分的返排液对地下水环境影响分析结果显示:返排液在入渗包气带后,受到阳离子交换作用,使Na~+、K~+、Ba~(2+)和Al~(3+)阳离子浓度减小。流经包气带的返排液与地下水混合发生水岩作用,改变了地下水原有的水化学类型(由HCO3·Cl-Ca型变为Cl-Na型)。水岩作用使Na~+、K~+、HCO3-浓度增加,Ca~(2+)浓度减小。返排液回注后,随返排液回注的CO_2会增加回注层方解石的溶解。(3)在返排液所含的75种目标有机物的淋溶迁移性评价中,3种(1,1-环丙二甲醇、2-甲基-1-丁烯和2-甲基-2-丁烯,占总数的4%)对地下水危害较大的有机物淋溶迁移性强,15种淋溶迁移性中等,其余57种淋溶迁移性弱;对于所研究的有机物,其淋溶迁移性指数GUS与log Koc(有机碳-水分配系数的对数)关系式为:GUS=-1.62 log Koc+6.42。说明其主要受吸附作用的影响,且淋溶迁移性随着吸附性的增强而降低。
[Abstract]:With the increase of natural gas demand, shale gas, as a new unconventional natural gas resource, has attracted more and more attention. Shale gas refers to unconventional natural gas occurring in reservoir rock series mainly rich in organic matter shale. Shale gas development in China started late, and the environmental impact and pollution causes caused by the development process are still lack of systematic study. On the basis of summarizing the previous research results, based on the actual conditions and data of a shale gas mining area in Sichuan Province, the hydrogeochemical simulation of shale gas production layer is carried out. Study on the influence of reflux liquid on groundwater environment and the evaluation of leaching migration of typical organic matter in the reflux solution. The results are as follows: (1) the simulation results of hydrogeochemical process of shale gas mining show that the dissolution of deep water-rock minerals is in order from fast to slow: carbonate minerals (calcite dolomite); Keywords feldspar minerals (potassium feldspar albite); pyrite; quartz; clay minerals (Illite, montmorillonite, chlorite, kaolinite); The concentrations of Ca~ (2), Mg~ (2), HCO3-,K~, Fe (t) and Al~ (3) in the solution increased continuously because of the dissolution of minerals, and the TDS in the solution increased nearly 4 times. The mineral dissolution of different shale rocks is proportional to the content of brittle minerals (the sum of quartz, feldspar and carbonate minerals). (2) High salinity. The results of the analysis of the effects of the reflux of complex components on the groundwater environment show that the reflux fluid is subjected to cation exchange after infiltration into the aeration zone, which reduces the cations concentration of Na~, K ~, Ba~ (2) and Al~ (3). The mixing of reflux fluid and groundwater through the aeration zone changes the original hydrochemical type of groundwater (from HCO3 Cl-Ca type to Cl-Na type). The concentration of Na~, K ~, HCO3- increases and the concentration of Ca~ (2) decreases. After reinjection, the dissolution of calcite increased with the reinjection of CO_2. (3) in the evaluation of leaching mobility of 75 kinds of target organic compounds in the reflux solution, 3 (1 ~ (1) cyclopropanediol, 2-methyl-1-butene and 2-methyl-2-butene, accounting for 4% of the total, have strong leaching migration to organic compounds that are harmful to groundwater, 15 species have moderate leaching mobility, and the remaining 57 species have weak leaching migration. For the organic matter studied, the logarithmic relationship between the leaching mobility index (GUS) and the organic carbon-water partition coefficient of log Koc (is as follows: GUS=-1.62 log Koc 6.42. The results show that it is mainly affected by adsorption, and the leaching mobility decreases with the increase of adsorption.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE377;X741

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