煤层气在基质孔隙中解吸传递机理及产能预测

项目名称： 煤层气在基质孔隙中解吸传递机理及产能预测

项目编号： No.U1262113

项目类型： 联合基金项目

立项/批准年度： 2013

项目学科： 地球物理学和空间物理学

项目作者： 石军太

作者单位： 中国石油大学（北京）

项目金额： 40万元

中文摘要： 煤岩发育有裂隙和基质孔隙双重孔隙，其中基质孔隙尺寸很小，但比表面积极大，孔隙表面吸附着大量的甲烷气。目前普遍认为，基质孔隙中的吸附气解吸后，首先在浓度差的作用下扩散进入割理（裂隙），然后以气水两相渗流的方式流向井筒。然而，基于扩散-渗流模型进行气井产能预测时，与实际生产曲线存在较大的偏差。通过研究发现，目前煤层气扩散理论忽视了基质孔隙中水的存在，使得扩散模型选择不妥，进而基于分子扩散而建立的产气模型存在一定的问题。因此，本课题拟从基质孔隙内的原始气水分布入手，研究含水基质孔隙中解吸气的相态特征及动力学行为，建立一个更准确的传递模型，进而建立相应的产能预测模型，揭示煤层气产气规律。本课题的研究将为煤层气界提供一套更准确的产能预测方法，为煤层气的合理开发提供科学依据。

中文关键词： 煤层气；解吸；动力学；渗流；数值模拟

英文摘要： Coal seams are dual porosity media containing two systems of fractures and matrix pores. The size of matrix pores is very small while specific surface area is large; a large amount of natural gas is adsorbed on the pore surface. It is generally believed that after the adsorbed gas desorbs, the desorbed gas in matrix pores first diffuses into cleats (fractures) under the driving of concentration difference, and then flows to the wellbore in the form of gas-water tow-phase flow. However, it is found that, predicted gas production based on the diffusion mechanisms of desorbed gas through matrix pores greatly deviate the actual production data. Through the preliminary research it is found that the diffusion theory ignores the existence of water in matrix pores, which makes the diffusion model inapplicable, and the gas production model based on the molecular diffusion has some problems. Therefore, we intend to start our study on the initial distribution of gas and water in matrix pores, and then construct a more accurate transport model by studying the dynamics and phase characteristic of gas in water bearing matrix pores. Based on the more accurate transport model, a corresponding gas production prediction model is established, and the gas production rule of coal-bed methane (CBM) is obtained. Our study will provide

英文关键词： Coal-bed Methane；desorption；kinetic；percolation；numerical simulation