超临界CO_2压裂煤岩储层增产煤层气应用发展前景

超临界CO_2压裂作为新兴渗透率强化技术以其对煤岩储层独特的物理化学力学特性改造,以及对储层近乎零损伤的特点受到了研究者的广泛关注。本文通过分析对比不同压裂介质作用下煤岩体的起裂压力与时间、裂缝扩展规律及渗透率变化,结果发现,水力压裂的裂缝扩展形式单一;液态CO_2压裂的衍生裂隙发育程度不高;超临界CO_2压裂形成的层理裂隙与衍生裂隙复杂程度高。特别地,超临界CO_2压裂煤体起裂压力比水力压裂低约39.48%,起裂时间是水力压裂的1.2倍以上,渗透率变化量是水力压裂的3倍左右。总体而言,超临界CO_2对煤储层的物理化学及力学特性的改造,为煤储层致裂增渗、增产煤层气理论与技术取得突破性进展提供了新思路与方法。

Application development prospects of supercritical CO2 fracturing to increase coalbed methane production

Supercritical CO2 fracturing, as a new permeability enhancement technology, has been widely concerned by researchers because of its unique physical, chemical and mechanical properties of coal reservoir and its near zero damage to the reservoir. In this paper, the fracture initiation pressure and time, fracture propagation rule and permeability change of coal and rock mass under the action of different fracturing media are analyzed and compared. It is found that the fracture propagation form of hydraulic fracturing is single; the development degree of derivative fracture of liquid CO2 fracturing is not high; the complexity of bedding fracture and derivative fracture formed by supercritical CO2 fracturing is high. Especially, the initiation pressure of supercritical CO2 fracturing coal is about 39.48% lower than that of hydraulic fracturing. The initiation time is more than 1.2 times that of hydraulic fracturing, and the change of permeability is about three times of that of hydraulic fracturing. Generally speaking, the transformation of the physical, chemical and mechanical properties of coal reservoirs by supercritical CO2 provides new ideas and methods for the breakthrough in the theory and technology of fracture and permeability enhancement and coalbed methane production.