韩城地区煤层气成因类型及微生物开发潜力

Coalbed methane generation and microbial-development potential in Hancheng Block

为重新梳理韩城地区煤层气气体地球化学特征,预测低产煤层气井微生物开发的潜力区,通过煤层气和煤层产出水样品采集、煤层气气体组分和稳定同位素组成测试及微生物多样性分析,判识煤层气的成因类型,计算煤层赋存热成因气和生物成因气的相对含量,讨论适合低产煤层气井微生物开发的潜力区。结果表明:韩城地区太原组煤层气气体组分以甲烷为主,平均含量为94.78%;煤层气气体类型是以热成因气为主并含有少量次生生物成因气的混合成因气,其中次生生物成因气占比为4.79%~28.28%;煤层产出水中优势古菌种属为Methanobacterium和Methanothrix,二者之和平均占比达45.45%。基于低产井煤层埋深、构造条件、水化学条件、储层温度和古菌群落结构等关键因素,认为韩城地区中部和南部井区是有利于煤层气生物实现增产目的的潜力区。

The geochemical characteristics of coal-bed methane(CBM)in Hancheng block are explored to predict the potential areas of microbial development in low-yield CBM wells.In this paper,the gas origin of CBM in this area were identified by collecting gas and water samples,testing the gas composition and stable isotope composition of CBM and analyzing the microbial diversity,and the relative contents of thermogenic gas and biogenic gas in the coal seam were calculated quantitatively,with the potential areas examined suitable for microbial exploitation of low-yield CBM wells in the study area.The results show that methane is the main gas component in Taiyuan Formation of Hancheng Block,with an average content of 94.78%;the gas genetic types in this area,mainly thermogenic gases,contain a small amount of secondary biogenic gases,of which the proportion of secondary biogenic gases is 4.79%~28.28%;the dominant archaea in the coalbed-produced water in this area were Methanobacterium and Methanothrix,the average proportion of which was 45.45%.Based on the analysis of key factors such as the depth of coal seam,structural conditions,hydrochemical conditions,reservoir temperature and archaeal community structure of low-producing wells,it is concluded that the central and southern well areas of Hancheng Block are the potential areas conducive to the implementation of CBM bioengineering and the improvement of gas production.