摘要
煤层气开发实践表明,产水量过高的煤层气井普遍存在低产气甚至不产气的现象,这成为煤层气开发低效的重要原因。为了分析异常高产水的主控因素,以沁水盆地柿庄南区块煤层气井为研究对象,基于区内大量的煤层气井生产资料,通过单因素方差分析及非线性拟合方法,确定了异常高产水的量化指标,并分析了不同因素控制下的异常高产水成因,探讨了相应的解决对策。研究结果表明:对于沁水盆地柿庄南区块排采时间已达8 a的高煤阶煤层气直井,异常高产水的量化指标为平均产水量大于3.22 m^(3)/d;区内煤储层上部砂岩含水层的发育是异常高产水的先决条件,复杂构造地质背景下的异常高产水现象更为普遍,北部断层和陷落柱附近发育密集程度不同的天然裂缝,异常高产水的高风险区为分别距离断层和陷落柱600,900 m范围内。在中南部弱构造活动区,水力压裂裂缝和局部水动力场成为异常高产水的主控因素,局部洼陷内煤层海拔越低,裂缝规模和高度越大,越容易导致异常高产水,且发育垂直或高角度倾斜剪切裂缝的煤层气井异常高产水的风险更高。因此,以远离断层和陷落柱等复杂构造为原则来布井,兼顾含水层发育特征与压裂裂缝规模的适应性,尤其是在局部洼陷内煤层海拔相对低点,控制煤层气井压裂裂缝规模以防沟通含水层,从而避免异常高产水导致煤层气井开发低效。
The operation of coalbed methane(CBM)shows that the phenomenon of low or even no gas production is common in CBM wells with high water production,which has become an important reason for the low efficiency of CBM development.In order to analyze the main controlling factors of abnormally high water production,taking the CBM wells in the Shizhuangnan Block of Qinshui Basin as the research object,based on a large number of production data of the CBM wells in the study area,the quantitative index of abnormally high water production was determined through a single factor variance analysis and non-linear fitting method.Moreover,the causes of abnormally high water production under the control of different factors were analyzed,and the corresponding countermeasures were discussed.The results show that the quantitative index of abnormally high water production is that the average water production is more than 3.22 m^(3)/d for the high rank CBM vertical well with 8-year drainage time in the Shizhuangnan Block in Qinshui Basin.The sandstone aquiferin the upper part of coal reservoir is a prerequisite for high water production.The abnormally high water production phenomenon is more common under a complex structural geological background.Natural fractures are developed near the fault and collapse column and the high risk areas are within 600 m and 900 m from fault and collapse column.In the weak tectonic activity area,the fractures caused by hydraulic fracturing and local hydrodynamic field become the main control factors.The lower the coal seam elevation in local sub-sag and the larger the fracture scale and height,the easier it is to lead to abnormally high water production.Also,the risk of CBM wells with vertical or high angle inclined shear fractures is higher.Therefore,the well location should be arranged according to the principle of keeping away from complex structures such as faults and collapse columns.In addition,it needs to consider the adaptability between aquifer development characteristics and fracturing fracture scale,especially it needs to control the fracturing fracture scale of CBM wells at the relative low elevation of coal seam in local sub-sags in order to prevent the communication with aquifer,so as to avoid the inefficient development of CBM wells.
作者
王凯峰
唐书恒
张松航
杨宁
郗兆栋
张迁
王敬宇
WANG Kaifeng;TANG Shuheng;ZHANG Songhang;YANG Ning;XI Zhaodong;ZHANG Qian;WANG Jingyu(School of Energy Resources,China University of Geosciences-Beijing,Beijing 100083,China;Key Laboratory of Marine Reservoir Evolution and Hydrocarbon Enrichment Mechanism,Ministry of Education,Beijing 100083,China;Beijing Key Laboratory of Unconventional Natural Gas Geological Evaluation and Development Engineering,Beijing 100083,China;Huadian Coal Industry Group Co.,Ltd.,Beijing 100035,China)
出处
《煤炭学报》
EI
CAS
CSCD
北大核心
2021年第S02期849-861,共13页
Journal of China Coal Society
基金
NSFC-山西煤基低碳联合基金重点资助项目(U1910205)
国家自然科学基金资助项目(41772159,41872178)
关键词
沁水盆地
高煤阶
煤层气
异常高产水
水力压裂
局部洼陷
Qinshui Basin
high rank
coalbed methane
abnormally high water production
hydraulic fracturing
local sub-sag
