四川盆地威远返排液元素地球化学特征及排放处理建议  

Geochemical characteristics of the elements in hydraulic fracturing flowback water from the Weiyuan shale gas development area in Sichuan Basin,China

作　　者：倪云燕[1,2] 姚立邈 廖凤蓉 高金亮 陈建平[1,2] 隋建立[3] 张蒂嘉[1,2] NI Yun-yan;YAO Li-miao;LIAO Feng-rong;GAO Jin-liang;CHEN Jian-ping;SUI Jian-li;ZHANG Di-jia(Key Laboratory of Petroleum Geochemistry,China National Petroleum Corporation,Beijing 100083,China;PetroChina Research Institute of Petroleum Exploration&Development,Beijing 100083,China;Institution of Geology,China Earthquake Administration,Beijing 100029,China)

机构地区：[1]中国石油天然气股份有限公司油气地球化学重点实验室,北京100083 [2]中国石油勘探开发研究院,北京100083 [3]中国地震局地质研究所,北京100029

出　　处：《天然气地球科学》2021年第4期492-509,共18页Natural Gas Geoscience

基　　金：国家重点研发课题(编号:2019YFC1805505);中国石油天然气股份有限公司直属院所基础研究和战略储备技术研究基金项目(编号:2017D-5008-08)联合资助。

摘　　要：水力压裂技术是页岩气开发的核心技术之一,大规模水力压裂技术可能会带来大量压裂返排液,而压裂返排液存在污染地下水和地表水等风险。综合对比分析四川盆地威远页岩气开发区压裂返排液与盆地内不同层系地层水地球化学特征,结果表明:威远页岩气返排液具有高矿化度、高含金属离子的特点,但与地层水相比,返排液中钠(7334 mg/L,n=63)、钙(297 mg/L,n=62)、锶(73.07 mg/L,n=64)、镁(32.1 mg/L,n=42)、钡(153.12 mg/L,n=64)、锰(1.83 mg/L,n=35)、锂(17.53 mg/L,n=64)、溴(72 mg/L,n=70)、氯(12578 mg/L,n=70)等含量基本上都是低于地层水,但硼含量(38.2 mg/L,n=64)与二叠系和三叠系地层水相近,低于震旦系和寒武系地层水。返排液B/Cl值、Li/Cl值和Na/Cl值基本都高于地层水,但Ca/Cl值和Br/Cl值则低于地层水。返排液、压裂注入液、寒武系地层水的溴氯含量具有很好的线性相关性(R2=0.9673),表明威远页岩气开发区返排液为压裂注入液与滞留在志留系页岩中的地层水的混合产物,且该地层卤水与寒武系相近。由于白云岩化作用,地层水具有富钙贫镁的特征,因此,返排液也具有富钙贫镁的特征。与生活饮用水卫生标准(GB 5749—2006)相比,返排液钠、氯、硼、钡、锰、铁、铊、SO42-等含量以及矿化度远高于前者,对环境具有潜在影响,不宜直接排放。威远返排液的处理主要采用循环利用方法,如果在循环利用之前能够根据返排液主微量元素的化学组成进行针对性前期处理,则可降低返排液复杂成分可能对页岩气产量与开采难度的影响,从而大大提高该方法的可行性。页岩气压裂返排液与常规地层水元素化学组成的差异性及其潜在环境风险的研究,为压裂返排液的处理与污染防控提供了重要的科学依据。Hydraulic fracturing technology is one of the core technologies of shale gas development.Large-scale hydraulic fracturing technology may bring a large amount of flowback water(including both flowback water and produced water),and flowback water has the risk of polluting groundwater and surface water.In this paper,the geochemical characteristics of flowback water from Weiyuan shale gas development area and formation water from different strata in Sichuan Basin are analyzed.The results show,flowback water in Weiyuan is characterized by high TDS and high content of heavy metal.However,compared to formation water,the contents of Na(7334 mg/L,n=63),Ca(297 mg/L,n=62),Sr(73.07 mg/L,n=64),Mg(32.1 mg/L,n=42),Ba(153.12 mg/L,n=64),Mn(1.83 mg/L,n=35),Li(17.53 mg/L,n=64),Br(72 mg/L,n=70),and Cl(12578 mg/L,n=70)in flowback water are basically lower than that of formation water.While the content of B(38.2 mg/L,n=64)in flowback water is similar to that of the Permian and Triassic formation water,but lower than that of the Sinian and Cambrian formation water.The ratio of B/Cl,Li/Cl and Na/Cl of flowback water is higher than that of formation water,but the ratio of Ca/Cl and Br/Cl of flowback water is lower than that of formation water.The flowback water,hydraulic fracturing fluid and Cambrian formation water has very good linear dependence between the contents of Br and Cl(R2=0.9673),which implies that flowback water was a mixture of the hydraulic fracturing fluid and the saline formation water retained in Silurian shale and the brine in this formation is similar to that in the Cambrian.Because of the dolomitization,formation water has the characteristic of enriched in calcium and depleted in magnesium,therefore,the flowback water also has such characteristic.Compared with the standards for drinking water quality(GB 5749-2006),the contents of sodium,chlorine,boron,barium,manganese,iron,thallium,SO42-and TDS of flowback water,are much higher than that of the former,which have potential impact on the environment and cannot be direc

关 键 词：返排液 地层水 页岩气 威远 四川盆地 环境影响 

分 类 号：TE122.113[石油与天然气工程—油气勘探]