煤层气储层损害机理及应对措施

针对山西沁水盆地南部中高阶煤储层,利用X射线衍射、溶剂抽提后质谱分析、扫描电镜、低温氮吸附和压汞法,测试了钻井液组分对煤岩有机分子结构、割理和基质孔隙的影响特征;开展了压力波动条件下,不同类型钻井液对煤储层应力敏感性、钻井液滤失量以及钻井液侵入后的储层损害的对比实验。分析认为减小煤层气储层损害需要综合考虑钻井液组分和钻井工程两方面因素,钻井液中淀粉类、纤维素类组分对煤岩的物理化学性质产生较大影响,压力波动是导致储层损害的主要推手。煤层气水平井钻井过程中,泡沫钻井液可以减少钻井液对煤储层的侵入量,清水钻井液侵入煤储层后的渗透率损害率最低,减小钻井压力波动是稳定井壁和保护储层重要工程措施。

Reservoir damage mechanism and protection measures for coal bed methane

The physical and chemical properties of high rank coal in Qinshui Basin under the action of single component of drilling fluid including permeability，organic macromolecular structure，matrix pore and cleat，et al，were comprehensively analyzed by the method of Xray diffraction，mass spectrometry analysis after solvent extraction，scanning electron microscope，low temperature nitrogen adsorption and mercury intrusion method.At the same time，stress sensitivity and invasion quantity in the pressure fluctuation，and reservoir damage after drilling fluid intrudes into coalbed were researched.Based on this work，the component of drilling fluid and drilling pressure are major factors for reservoir damage，starch and cellulose of drilling fluid will change the physical and chemical structure of coal，pressure fluctuation is main driving force.Foam drilling fluid can effectively avoid invading into reservoir，reservoir damage rate of water drilling fluid is the lowest after invasion，drilling pressure fluctuations should be reasonable controlled based on the purpose of borehole stability and protect reservoir.