柿庄北深煤层压裂伤害机理及低伤害压裂液评价

我国煤层气地质资源量达36.81×108m3,仅次于俄罗斯和加拿大,其中1 000~2 000 m的煤层气地质资源量占总资源量的61.2%。深煤层煤层气的开发是今后煤层气开发的必然趋势。水力压裂是深煤层煤层气工业开采的主要增产措施。在分析柿庄北深煤层的工程地质特征时发现,深煤层具有低孔隙度、低渗透率、高变质程度和高含气量的特点,在压裂改造时易受工作液体的伤害。因此,针对煤岩主要的伤害类型,对比分析压裂液伤害前后的煤岩电镜扫描结果,研究深煤层煤岩的伤害机理。通过研究得出,相对浅煤层而言,深煤层主要的伤害是吸附伤害和微粒堵塞。最后,根据深煤层岩心的伤害评价方法,在实验室内分别优选出低伤害活性水和泡沫压裂液两种体系,伤害评价结果显示优选的活性水和泡沫压裂液对深煤层的伤害率相对常规压裂液低,可在一定程度上改善煤层气储层压裂效果。

Fracturing damage mechanisms of deep coal seams and assessments of low damage fracturing fluids: the deep coal seam in the north of Shizhuang on the Qinshui basin

The amount of coalbed methane (CBM) in China is 36.81×10₈m₃, next only to Russia and Canada, while the resource between 1000 and 2000m makes up 61.2% of the total amount. In the future, the exploitation, which needs hydraulic fracturing as the major stimulation, of CBM in deep coal seams is an inevitable trend. Deep coal seams which are more damaged in the fracturing have the features of low porosity, low permeability, high metamorphic grade and high gas content. Therefore, aiming the damage types of coals, the results of scanning electron microscope (SEM) for coals are analyzed comparatively, and the damage mechanisms of deep coal seams are studied. Compared with shallow coal seams, adsorption and particle plugging are major damages for deep ones by studying. Finally, according to the damage evaluation method of cores, the two systems of low damage active water and foam fracturing fluid are selected in the lab, and experimental results show that the damage from them is lower than that from common fluids, which can improve the fracturing effect of CBM reservoirs to some extent.