煤层气单井产量影响因素分析

ANALYSIS ON PRODUCTION-AFFECTING FACT-ORS OF SINGLE WELL FOR COALBED GAS

煤层气主要以吸附状态赋存在煤岩基质中,只有当储层压力降低后才可以从基质中解吸出来,煤岩 裂隙或割理中多被水充满,而裂隙与割理是煤层中的主要运移通道,煤层气需要通过排水(裂隙或割理)降压(煤岩 储层)方式才得以采出,故煤层气的产量受煤岩性质、压力水平和两相渗流特征等多种因素的影响。文章分析认 为,影响煤层气井单井产量的主要因素包括煤岩渗透率、孔隙度、吸附能力、含气量、临界解吸压力、相对渗透率等; 为提高煤层气井单井产量,必须通过洞穴完井、压裂改造或水平井等方式,改善井底渗流条件,有效地降低井底流 压,扩大压力波及范围,增加有效解吸区,扩展两相渗流区范围。为实现煤层气的规模开发,必须深化认识储层特 征,结合地质实际,选择合适的开发技术。

Coal-bed gas exists in the coal matrix mainly as adsorption state. It can't discharge by desorption until the reservoir pressure drops. Most of fractures and cleats in coal rocks are filled by water. The fractures and cleats are the main migration channels of coalbed gas. Coal-bed gas can't be exploited until water draining and pressure dropping. So, the production of coalbed gas is affected by many factors such as the property of coal rocks, the pressure level and the features of bi-phase percolation etc. The article thinks the main factors to affect the production of a single well for coal-bed gas include permeability, porosity, adsorption ability, gas content, critical desorption pressure, and relative permeability etc. To improve the production of a single well for coal-bed gas, it is necessary to improve the per colation conditions of bottom hole, reduce the production pressure of bottom hole effectively, expand the range of pressure sweep, increase the effective desorption zones, and expand the range of bi-phase percolation region by the way of cave completion, fracturing stimulation, or horizontal drilling etc. To realize the commercial development of coal-bed gas, it is necessary to understand the features of the reservoirs deeply, and select the proper exploiting techniques according to the geological conditions.