云南老厂雨旺区块煤层气井产出水化学特征

Hydrochemical Characteristics of Coalbed Methane Well in Yuwang Bolck,Laochang,Yunnan Province

基于云南老厂矿区雨旺区块煤层气地质条件和6口煤层气先导试验井产出水样品的常规离子测试,分析了区内煤层气井产出水化学特征、离子变化规律及其与产能的关系。结果表明:研究区煤系含水层自老厂背斜核部接受大气降水补给,整体称单斜向东南径流,并受次级褶皱和断层影响;煤层气井产出水阳离子以Na^(+)+K^(+)为主,Ca^(2^(+))、Mg^(2^(+))含量较低,阴离子以HCO_(3)^-和Cl^-为主,矿化度介于1465~5625 mg/L,水型主要为Na^-HCO_(3)·Cl和Na^-Cl·HCO_(3),与压裂液水型相似。溶滤作用在研究区内普遍存在,脱硫酸作用强度较大,阳离子交替吸附作用强度较小,脱碳酸作用较弱。综合分析煤层气井产出水化学特征和研究区产能特征可知:当前煤层气井主要产出压裂液,煤层本身产水较低,导致压降漏斗扩展范围较小,降压效果较差,煤层气解吸量较少,产能较低。

Based on the coalbed methane(CBM)geological conditions of Yuwang block,Laochang minging area,Yunnan Province,and the conventional ion measurement of the produced water by 6 pilot test CBM Wells,the chemical characteristics of the produced water,ion change rules and their relationship with productivity were analyzed.The results show that the coal measure aquifer in the study area receives meteoric water recharge from the core of Laochang anticline,presents a monoclinal southeast runoff and is affected by secondary fold and fault.The cation of CBM well produced water is mainly Na^(+)+K^(+),with low Ca^(2^(+))and Mg^(2^(+))contents.The anion are mainly HCO_(3)^-and Cl^-,and the salinity is between 1465 mg/L and 5625 mg/L.The water types are mainly Na^-HCO_(3)·Cl and Na^-Cl·HCO_(3),which are similar to the water type of fracturing fluid.Dissolution and filtration are common in the study area,the desulfurization acid is strong,cation alternate adsorption and decarbonization are weak.The characteristics of CBM produced water and the productivity of the research area were analyzed comprehensively.The results show that CBM wells mainly produce fracturing fluid now,which lead the water production of coal seam itself is low,leading to a small expansion range of pressure drop funnel,poor pressure reduction effect,and low coalbed methane desorption capacity and low productivity.