钻井完井过程中煤层气储层伤害机理分析与控制措施

Formation Damage Factor Analysis and Control Measures for Coalbed Methane Reservoirs during Drilling Process

本文综述了中国煤层气储层具有低渗透率、低压力、低含水饱和度的特征,提出钻井完井过程中引起储层伤害的主要因素是应力敏感和水锁。为了防止储层伤害,钻进过程中应首先考虑使用空气钻井,其次考虑使用可循环泡沫钻井液和水包油可循环泡沫钻井液体系。对于水平井和定向井,可考虑使用玻璃漂珠钻井液体系,实现近平衡压力钻井。固井时应采用低密度、低滤失量和高强度水泥浆体系。

In China, stress sensitivity and water lock are the key factors in understanding and controlling drilling-sustained CBM reservoir damage. For formation damage control, low density and low filtration drilling fluid systems are required during the drilling process. For vertical wells air drilling is the best choice for a stable formation. For formations that have problems with water outlet and stabilization, normal and oil based recyclable micro-foam drilling fluids can be used. For horizontal wells and directional wells, Hollow Glass Sphere （HGS） drilling fluid systems can be selected to implement near balanced drilling. For ecementing, a low density/low fluid loss and high strength slurry should be adopted.