沁水盆地原始水动力场类型及其对煤层气排采的影响

Original Hydrodynamic Patterns and Their Influence on Coalbed Methane Drainage in Qinshui Basin

水动力场研究在煤层气勘探开发中具有重要作用。本文首先讨论了基于煤层气井排采资料的水动力场研究方法,在分析沁水盆地柿庄区块原始水动力场特点的基础上,结合前人在盆地其他区块水动力场的研究成果,分析了沁水盆地原始水动力场的类型,进而探讨了水动力场类型对煤层气排采的控制作用。研究表明:沁水盆地自边缘向腹部依次存在重力驱动型、滞流型和压实驱动型三种类型的区域原始水动力场;重力驱动型和滞流型水动力场具备煤层气保存条件,含气量高,煤层气排采效果相对较好,而压实驱动型水动力场虽具备一定的保存条件,但因地层压力较高,煤层气井排水降压困难,产气效果较差;无论是在重力驱动型还是滞流型的区域水动力场中,局部的低势汇聚区具备煤层气保存和排采的有利条件,煤层气开发效果一般较好。在未来煤层气勘探开发过程中,应将重力流驱型或滞流型水动力场所在区域中的局部低势汇聚区作为煤层气开发的甜点区。

Objectives： Qinshui basin is one of main coalbed methane basins in China, where the studies on hydrogeology patterns are relative weak now, due to lack of data. This paper aims to discuss the hydrodynamic patterns and their influence on coalbed methane drainage in Qinshui basin.Method： Based on the former research results and analysis of coalbed methane （CBM） well performance data acquired in recent years in Shizhuang CBM block, this paper discussed firstly hydrodynamics study method through well performance data interpretation. The characteristics of hydrodynamics in Qinshui basin were then discussed and the knowledge about hydrodynamics in the basin were extended, and finally the types of hydrodynamics and their control on CBM development in different CBM blocks were analyzed in Qinshui Basin.Results： There are three types of regional hydrodynamics including the gravity driven flows, stagnant flows and compaction driven flows from the edge to the central of Qinshui basin. Gravity driven flows and stagnant flows are beneficial to coalbed methane development. As for compaction driven flows, however, is harmful to coalbed methane development since its high reservoir pressure leading to inefficient depressurization of CBM wells. Conclusions： Whatever the hydrodynamics type is gravity driven flows or compaction driven flows, the local converged area with good condition for preserving and draining has a favorite development result. In the process of CBM exploration and development in the future, in order to maximize production and benefits, the local converged area should be sweet spot of CBM development.