沁水盆地樊庄区块煤系水分布及其对排采效果的影响

Distribution of Coal Measures Water in Fanzhuang Block of Qinshui Basin and Its Impact on Drainage Effect

樊庄区块为高煤阶煤层气田具有典型代表性的区块之一,精细化表征煤系水的分布特征,分析其控气作用,对于指导类似区块煤层气开发意义重大。据此,采用数理统计、回归分析及数据拟合的方法,建立了煤层及砂岩的测井识别特征,构建了含水量计算模型,探究了煤系水分布与排采效果之间的关系。研究表明:研究区3#煤层测井识别特征为高电阻率(853.86~5 968.9Ω·m),低体积密度(1.26~1.49 g/cm^(3)),低自然伽马(18.4~60.51API);砂岩含水层测井识别特征为低电阻率(70~316.2Ω·m),高体积密度(2.51~2.68g/cm^(3)),低自然伽马(56.4~116.19API);研究区纵向上岩性以煤、泥岩、砂岩及砂质泥岩为主,横向上煤层分布稳定,砂岩含水层分布不均匀,井控水量区域差异性大;研究区煤层分布较为稳定,在不考虑二次压裂影响的情况下,将累计产水量1 200m^(3)作为煤层是否接受外来水源补给的界线;煤层气井开发过程中,在构造及沉积条件相似的情况下,煤系水的来源越广泛、规模越大,则煤层气井见气时间越久、排水降压阶段持续时间愈长,产水量越高、产气量越低。

The Fanzhuang block is one of the typical representative blocks of high coal rank coalbed gas fields.Fine characterization of the distribution characteristics of coal measures water and analysis of its gas control effect are of great significance for guiding the development of coalbed methane in similar blocks.Based on this,mathematical statistics,regression analysis,and data fitting methods were used to establish the logging identification characteristics of coal seams and sandstones,construct a water content calculation model,and explore the relationship between the distribution of coal bearing water and the drainage effect.Research has shown that the logging identification characteristics of the 3#coal seam in the study area are high resistivity(853.86~5968.9Ω·m),low bulk density(1.26~1.49 g/cm^(3)),and low natural gamma(18.4~60.51API).The logging identification characteristics of sandstone aquifers are low resistivity(70~316.2Ω·m),high bulk density(2.51~2.68g/cm^(3)),and low natural gamma(56.4~116.19API).The vertical lithology of the research area is mainly coal,mudstone,sandstone,and sandy mudstone.The horizontal distribution of coal seams is stable.The distribution of sandstone aquifers is uneven,and there are significant regional differences in well control water volume.The distribution of coal seams in the research area is relatively stable.Without considering the impact of secondary fracturing,the cumulative water production will be 1200 m^(3) as the boundary line for whether coal seams receive external water supply.In the development process of coalbed methane wells,under similar structural and sedimentary conditions,the wider and larger the source and scale of coalbed water,the longer the gas occurrence time,the longer the duration of drainage and pressure reduction stage,and the higher the water production and lower the gas production.