准南煤层中H2S的赋存状态及其水溶液对煤储层的酸化增渗机制

The coal reservoir with abnormal high H2S content commonly presents higher permeability in Junggar Basin. Therefore, the geological background of the enrichment of H2S would be studied in detail, the adsorbed H2S content of the coal can be measures from the isothermal adsorption tests, the dissoloved and free content of H2S under the situ strata condition with the physical and numerical simulation can be acquired, and the occurrence state of H2S can be raised. The acidification experiments of H2S solution with coal under situ strata condition would be launched, and the differences among the pore structure, pore types, fractures and permeability of coal at both the vertical stratification and horizontal stratification directions would also be discussed before and after the H2S solution acidification, the response characteristics between the coal and the H2S solution can be put forward. According to the detailed comparative analysis of the shape of the pores and fractures, the types of the organic and the content of inorganic mineral before and after the H2S solution acidification, the permeability enhancement mechanism of acidification with H2S solution on coal can be acquired. The research work can efficiently and safely guide the coal mining and predict the enrichment of coalbed methane with the abnormal H2S content in southern Junggar Basin, Xinjiang.

针对研究区煤层瓦斯中H2S异常偏高地区煤储层渗透性普遍较好的地质现象，在系统分析H2S富集区地质背景的基础上，实测煤层中吸附H2S的含量、物理模拟和数值模拟原位地层条件下煤系水中溶解H2S的含量及煤层中游离H2S的含量，揭示H2S在煤层中的赋存状态；物理模拟原位地层条件下煤储层与H2S水溶液的酸化反应过程，对比分析酸化前后煤储层孔隙结构、孔隙类型、裂隙特征及不同层理方向渗透率的变化规律，揭示煤岩体对H2S水溶液酸化处理的响应特征，探讨酸化处理对煤中孔隙和裂隙、有机质和无机矿物、不同类型无机矿物的影响规律，揭示H2S水溶液对煤储层的酸化增渗机制。研究对新疆准南H2S异常矿井的高效安全生产及煤层气有利区的预测具有理论和现实意义。

从地域、层域、赋存状态、煤阶、成因类型、浓度等方面系统分析了我国煤储层H2S异常区的分布特征；通过开展煤矿瓦斯现场解吸和残余气测定、煤层瓦斯和煤层气组分分析及煤层水中H2S浓度测试，揭示了准南煤田阜康矿区KL煤矿和CS煤层气井区吸附态及游离态H2S含量，KL煤矿煤层中H2S含量介于1.246×10-6~8.706×10-6m3/t，平均H2S含量为4.712×10-6m3/t，CS煤层气井区煤层中H2S含量介于1.702×10-6~36.584×10-6m3/t，平均H2S含量为13.570×10-6m3/t，煤层水中H2S含量介于0.05~30.16μg/L，平均含量为4.65μg/L，煤层水中H2S含量主要分布在0.05~0.24μg/L区间内；首次开展了饱和H2S水溶液酸化前后煤岩体孔渗特征的对比实验，对比研究了酸化前后孔隙度、不同层理方向渗透率、孔容、孔比表面积、孔径分布、孔隙分形特征等的变化规律，证实了H2S水溶液酸化作用对煤储层孔渗特征的改善作用，酸化后孔隙度增大且低阶煤的孔隙度增幅明显高于中阶煤，H2S水溶液酸化后煤样的渗透率明显增大且低阶煤的渗透率增幅明显高于中阶煤，平行层理方向的渗透率增幅明显高于垂直层理方向；探讨了H2S水溶液对碳酸盐矿物、黏土矿物等矿物的影响，揭示了H2S水溶液对煤储层的酸化增渗机制，一方面是酸化作用引起碳酸盐矿物与酸液发生溶蚀作用，导致充填于孔隙、裂隙中的方解石等碳酸盐矿物被溶蚀，从而使得空隙体积增大、连通性增强的正效应；另一方面是酸化作用导致煤中黏土矿物膨胀、分散形成的细小颗粒和黄铁矿反应生成的沉淀堵塞孔隙，造成空隙体积减小、连通性减小的负效应，低阶煤以正效应为主，中阶煤以负效应为主。