四川筠连煤层气井产出水地球化学特征及地质意义  

Geochemical characteristics and geological significance of produced water from coalbed methane wells in Junlian,Sichuan

作　　者：顾俊雨 杨兆彪[1,2] 田文广[3] 韩永胜 刘常青 梁宇辉 卢本举 李存磊 彭丽莎 王海晨 GU Junyu;YANG Zhaobiao;TIAN Wenguang;HAN Yongsheng;LIU Changqing;LIANG Yuhui;LU Benju;LI Cunlei;PENG Lisha;WANG Haichen(Key Laboratory of Coalbed Methane Resources and Reservoir Formation Process,Ministry of Education,China University of Mining and Technology,Xuzhou 221008,China;School of Resources and Geosciences,China University of Mining and Technology,Xuzhou 221116,China;Research Institute of Petroleum Exploration and Development-Langfang Branch,Langfang 065007,China;PetroChina Zhejiang Oilfield Company,Hangzhou 310023,China)

机构地区：[1]中国矿业大学煤层气资源与成藏过程教育部重点实验室,江苏徐州221008 [2]中国矿业大学资源与地球科学学院,江苏徐州221116 [3]中国石油勘探开发研究院,河北廊坊065007 [4]中国石油浙江油田公司,浙江杭州310023

出　　处：《煤炭学报》2025年第3期1647-1658,共12页Journal of China Coal Society

基　　金：国家自然科学基金资助项目(42272195,42130802);中国石油天然气股份有限公司“十四五”前瞻性基础性重大科技资助项目(2021DJ2303)。

摘　　要：煤层气井排采水地球化学特征包含着丰富的地层水来源信息,可反映煤层气保存条件,对煤层气富集机理和勘探开发研究具有重要意义。以四川盆地南缘筠连区块9组19口典型煤层气井为研究对象,开展了产出水常规离子、微量元素、氢氧同位素实验测试,并结合产出水常规离子随排采时间变化规律探讨煤层气井产出水的来源。结果表明:筠连区块煤层气井产出水中Na^(+)+K^(+)含量超过90%,溶解性固体(TDS)总质量浓度为1203~143099 mg/L,Cl^(-)质量浓度为709~SO_(4)^(2) HCO_(3)^(-)85700 mg/L,质量浓度为12~3614 mg/L,质量浓度为24~516 mg/L,具有“高TDS、SO_(4)^(2) HCO_(3)^(-) SO_(4)^(2)高Cl^(-)、高、低”的特征。在10 a排采期间,Cl^(-)表现为波动性下降,前期含量较为HCO_(3)^(-)稳定,约为20~25 mEq/L,在排采1500 d左右开始出现波动,含量最低。筠连煤层气井产出水主要存在海相成因的原始沉积水、大气降水补给的渗入水与混合水3种类型,产出水变化在时间与空间尺度上均显示了一个大气降水渗入到原始沉积水的混合过程。随着大气降水的渗入,产出水水型由Ca/Mg-Cl型先转变为Na-SO4型,再转变为Na-HCO3型;微量元素含量逐步减少,其中Sr与B元素对产出水来源的敏感性较高;产出水氢氧同位素值逐渐减小,氢氧同位素拟合线也逐渐向大气降水线靠近。多种地球化学指标均显示处于宽缓向斜轴部的G1-2井封闭性较好,产出水主要为海相沉积水,而处于向斜翼部的G3井封闭性较差,来源主要为大气降水,其余井介于二者之间,为古海水与大气降水的混合水。The geochemical characterization of coalbed methane(CBM)well drainage water contains rich information on the source of formation water,which can reflect the conditions of CBM preservation,and is of great significance to the study of CBM enrichment mechanisms and exploration and development.Taking 19 typical CBM wells in 9 groups of the Junlian block at the southern margin of the Sichuan Basin as the research objects,experimental tests of conventional ions,trace elements,hydrogen and oxygen isotopes of produced water were carried out,and the source of produced water in CBM wells was discussed in combination with the variation law of produced water conventional ions with drainage time.The results show that the Na^(+)+K^(+)ratio in the produced water of coalbed methane wells in Junlian block is more than 90%,SO_(4)^(2) HCO_(3)^(-)and the TDS is 1203~143099 mg/L,the Cl^(-)is 709~85700 mg/L,the is 12~3614 mg/L,and the is 24~SO_(4)^(2) HCO_(3)^(-)4516 mg/L,which is unique characteristics of“high TDS,high Cl^(-),high,and low”.During the ten-year dis-SO_(4)^(2)charge period,Cl^(-)showed a fluctuating decrease;was more stable at about 20-25 mEq/L in the early stage and HCO_(3)^(-)began to fluctuate around 1500 d;and was the lowest.There are mainly three types of produced water in Junlian CBM wells:primary sedimentary water of marine origin,infiltrated water recharged by atmospheric precipitation,and mixed water,and the change of produced water shows a mixing process from infiltration of atmospheric precipitation to primary sedimentary water in both time and space scales.With the infiltration of atmospheric precipitation,the water type of produced water changes from Ca/Mg-Cl type to Na-SO_(4) type and then to Na-HCO_(3) type;the content of trace elements decreases gradually,among which Sr and B elements are more sensitive to the source of the produced water;the hydrox-ide isotope value of the produced water decreases gradually,and the hydroxide isotope fitting line is gradually close to the meteoric water line.Various

关 键 词：川南筠连 煤层气 产出水 地球化学特征 地质意义 

分 类 号：P618.1[天文地球—矿床学] P592[天文地球—地质学]