低透煤层化学改性增透技术研究现状及展望

我国煤储层的赋存特征概括为微孔隙、强吸附、低渗透，这些赋存特征严重抑制了煤层气的开采，在此基础上，储层改造技术被广泛提出。针对低透气性煤层，国内外学者提出水力压裂、水力割缝、预裂爆破等储层增透技术，这些技术均存在增透范围小、裂隙闭合快、水锁效应等问题。有学者提出采用化学方法改造煤层，利用化学试剂改变煤层理化性质继而达到促进煤层气解吸、渗流的目的。化学储层改造方法主要包括煤层酸化、氧化、萃取、电化学处理，酸化增透即通过酸液溶蚀煤中矿物质，从而疏通孔裂隙、增大渗透率；氧化增透则是利用氧化剂腐蚀煤层割理表面或溶解部分煤基质来增加煤层割理孔径；萃取增透则使用有机溶剂提取煤体中的有机小分子，疏通孔隙；电化学处理就是通过电化学反应使得煤结构发生变化、产生气体和煤体温度升高，瓦斯运移通道增大。回顾国内外低透气性煤层化学改性增透技术的研究进展，从酸化、氧化、萃取、电化学处理4个层面深入分析了煤层化学改性的增透机理，阐释了目前化学储层改造技术所面临问题与未来的发展趋势。

Research status and prospect of chemical modification and permeability enhancement technology for low permeability coal seam

The occurrence characteristics of coal reservoirs in China are summarized as micropores,strong adsorption and low permeability.These occurrence characteristics seriously inhibit the exploitation of coalbed methane.On this basis,reservoir reconstruction technology is widely proposed.Aiming at low permeability coal seam,scholars at home and abroad put forward reservoir permeability enhancement technologies such as hydraulic fracturing,hydraulic cutting and presplitting blasting.These technologies have some problems,such as small permeability enhancement range,fast fracture closure and water lock effect.Some scholars put forward to use chemical method to transform coal seam,that is to use chemical reagent to change physical and chemical properties of coal seam,so as to promote desorption and seepage of coalbed methane.Chemical reservoir modification methods mainly include coal seam acidification,oxidation,extraction and electrochemical treatment.Acidizing and permeability enhancement means that acid solution can dissolve minerals in coal,so as to dredge pores and fissures and increase permeability;Oxidation and permeability enhancement is to increase the pore size of coal cleat by using oxidant to corrode the surface of coal cleat or dissolve part of coal matrix;in addition,organic solvents are used to extract small organic molecules in coal to dredge pores;electrochemical treatment is to change the coal structure,produce gas and increase the temperature of coal body,and increase the gas migration channel through electrochemical reaction.This paper reviews the research progress of chemical modification of low permeability coal seam at home and abroad,analyzes the mechanism of chemical modification of coal seam from four aspects of acidification,oxidation,extraction and electrochemical treatment,and explains the problems and future development trend of chemical reservoir modification technology.