煤层压裂开采与治理区域瓦斯的基本问题

由于煤层的矿物成分、结构体系、瓦斯的吸附解吸效应等导致含瓦斯煤层水压致裂复杂,煤层压裂治理区域瓦斯技术目前整体上还处于起步阶段。提出了煤层水压(流压)致裂治理区域瓦斯的理论、技术与装备等基本问题框架。在分析煤层物理化学特性的基础上,初步给出了煤层压裂的力学机制与裂缝基本空间形态。分析了含瓦斯煤层水压致裂的物理化学作用、结构改造增透、应力扰动效应、驱赶瓦斯效应、水锁效应等作用。以孔隙压力梯度作用机制为切入点,深入研究煤岩层压裂的细观破裂机理、应力扰动效应与评价方法、体积致裂机制、驱赶瓦斯效应、支撑剂在裂缝网络的运移规律与压嵌特性、排采规律等理论问题。针对驱赶瓦斯效应扬长避短,使含瓦斯煤层压裂上升至压裂驱赶层次。提出了需要深入研究的技术安全性评价、工艺技术、合理泵注排量、压裂裂缝扩展及其效应监测、适用条件与规范等技术问题。研制了井下压裂治理区域瓦斯的致裂封孔系统、分析软件与测控系统等成套装备。

Basic problems of hydraulic fracturing for mining and control zone gas in coal seams

The mineral composition,structural system and gas adsorption and desorption effects result in the complexity of hydraulic fracturing in gassy coal seam.The technology of coal seam hydraulic fracturing for regional gas control is still at its initial stage at present.Basic framework of theory,technology and equipment of coal seam hydraulic (fluid) fracturing for regional gas control was proposed.Based on the analysis of physical and chemical property of coal seam,mechanic mechanism of coal seam hydraulic fracturing and the basic spatial morphology of hydraulic fracture were preliminarily given.The effects of physical and chemical process,structural transformation,permeability increasing,stress disturbance,displacement methane and water lock of hydraulic fracturing were analyzed.Took the pore pressure gradient as entry point,intensive study should be conducted on the theoretical problems of coal seam hydraulic fracturing.The theoretical problems include the mesoscopic fracture mechanism,the stress disturbance effect and evaluation methodology,the mechanism of volume fracturing mechanism,the displacement methane effect,the migration law and embedding property of the proppant,and the drainage and mining law.As for the displacement methane effect,its advantages should be used and its disadvantages should be by passed to upgrade hydraulic fracturing for gassy coal seam to hydraulic fracturing displacement methane level.Technical problems such as technology security evaluation criteria,technology,reasonable pumping flow,monitoring of the hydraulic fracture propagation and its effect,application condition and standard require deep-going researches.A set equipment of hole sealing system,analysis software and measurement and control system were developed for underground coal seam hydraulic fracturing for regional gas control.