1. School of Resource and Geosciences,China University of Mining and Technology,Xuzhou　 221116,China; 2. Key Laboratory of CBM Resources and Dy- namic Accumulation Process,Ministry of Education of China,China University of Mining and Technology,Xuzhou　 221008,China; 3. Guizhou Research Center of Shale Gas and CBM Engineering Technology,Guiyang　 550009,China

基于松河和织金区块16口煤层气井产出水样品的常规离子,微量元素,氢氧同位素测试,结合其地质背景、产能特征,对比分析了两区块产出水地球化学特征及其对产能的指示意义。研究表明:松河产出水Cl-,Na+质量浓度高度异常,水质为Na-Cl型,表明地层水受压裂液污染;织金产出水来自煤层,Na+和HCO-3富集,水质为Na-HCO3型,反映出较封闭的地下水环境。松河和织金产出水均表现出明显的D漂移特征,且松河区块煤中氢氧同位素组成较重。除Li元素外,松河产出水中大部分微量元素溶出量均大于织金。提出了更具普适意义的反映地层水环境的封闭性指数。封闭性指数和日产气量、累计产水量相关关系显著,中等封闭指数更有利于实现高产,可提取作为评价产能潜力的地化指标,并初步建立了基于HCO-3和Cl-质量浓度的产出水来源判识模板,划分出两个区域:低产井产出压裂液区和高产井产出煤层水区。

Based on the conventional ion,trace element and hydrogen and oxygen isotope test of 16 CBM wells pro- duced water in Songhe and Zhijin blocks,combined with its geological background and productivity characteristics,the geochemical characteristics of the two blocks’s produced water and significance to production capacity are compared and analyzed. Research shows that,the concentration of Cl- and Na+ in Songhe produced water is abnormally high and the water quality is Na-Cl,indicating that formation water is polluted by fracturing fluid. The water produced in Zhijin comes from coal seams,the Na+ and HCO- are enriched and the water quality is Na-HCO3 ,reflecting the relatively closed groundwater environment. Both the Songhe and Zhijin produced water show obvious D drift characteristics,and the higher content of hydrogen and oxygen in the coal of Songhe area lead to the heavier hydrogen and oxygen isotopic composition in the produced water. Except Li element,the dissolution of most trace elements in Songhe produced water are greater than that of Zhijin block. A more universal closeness index reflecting formation water environment is put forward. The correlation between the closeness index and daily output and accumulated water yield is significant,the medium closeness index is more conducive to achieving high yield,and it can be extracted as the geochemical index to evaluate productivity potential. The identification template of production water source based on HCO- and Cl- concen- tration is preliminarily established,and two zones are divided:low-yield wells producing fracturing fluid zone and high- yield wells producing coal seam water zone.

WU Congcong,YANG Zhaobiao,QIN Yong,et al. Geochemical comparison and its geological significance of CBM produced water in the Songhe and Zhijin blocks[J]. Journal of China Coal Society,2018,43(4):1058-1064.