超声激励低渗煤层甲烷增透机理

超声激励增透煤层是一种不受甲烷储层地质条件和气源特性限制,具有普遍应用价值的增采技术.但由于煤岩致密、裂隙发育,煤岩孔隙度存在多尺度效应,受储层介质尺度效应影响的增透促吸机理尚不明确.本文通过CT观测实验和渗透率测定实验,对超声波作用下煤样不同尺度裂隙发展规律进行了分析,对比测定超声作用煤样渗透率变化规律,建立了超声增透煤层甲烷渗透率的修正公式.研究结果表明:CT观测实验很好地证明了超声的机械震碎作用;在声场衰减范围内,煤体损伤和机械震碎作用明显;超声波作用后的煤层渗透率有平均135%～169%的提高.研究工作为超声激励增加煤层的渗透率提供了实验基础.

Mechanism of methane permeability enhance through ultrasonic irradiating on low permeable coal seam

Ultrasonic irradiation enhancement of coal seam methane is a kind of technology with general applicable value, which is not limited by reservoir geologic conditions and source gas characteristics. However, because of the reservoir densification, there exist scale effects such as matrix pore throat scale and the natural crack dimensions overlap, the reservoir medium permeability enhancement and extraction promotion mechanism is not clear. This article used CT observation experiment and permeability measurement experiment to analyze the rule of fracture development of different scales in coal samples under ultrasonic effect, compared the change of coal sample permeability by ultrasound effect, and established the modified formula of ultrasound enhancement of coal seam methane permeability. Research results show that: CT observation clearly proved the ultrasonic mechanical shattering effect; within the attenuation scope of ultrasound, coal body damage and mechanical shatter effect are obvious; permeability of coal seam increased 135%～169% on average by ultrasonic irradiation. Research work provides experimental basis for increasing the permeability of coal seam by ultrasonic irradiation.