College of Geoscience and Surveying Engineering, China University of Mining and Technology (Bejing) Coalbed
Methane Pilot Exploitation Test Base, CNPC

基于煤层孔隙结构是影响煤层气吸附及渗流的重要因素,为了揭示高压注水过程中煤孔隙结构的变化规律。采用核磁共振试验、渗透率试验及显微镜观测微裂隙方法,从微观上研究高压注水对煤孔隙结构的影响,为研究煤层气水力压裂技术提供微观层次的理论依据。通过核磁共振试验得知经高压注水后单位体积（1 cm3）煤各孔隙类型孔隙体积都得到增大,其中中孔孔隙体积平均增大0.73×10-3cm3,增量最小;小孔孔隙体积平均增大8.79×10-3cm3,增量最大。通过光学显微镜观测得知高压注水有利于裂隙连通、产生新裂隙及增大裂隙宽度,从而使煤渗透率比高压注水前增大146%560%。通过煤渗透率测试得知微孔和小孔主要起吸附及解吸作用,对煤的渗透性基本没有贡献,大孔对煤的渗透率贡献最大,是煤渗流及运移的主要通道,中孔次之。

During high-pressure water injection process on coal seam, change laws of pore structure of coal seam were revealed, while the pore structure of coal s eam was an important influential factor to the gas adsorption and seepage of coal seam. With the methods of nuclear magnetic resonance experiment, permeability exp eriment and observing microfissuring through light microscope, the influence of high-pressure water injection on pore structure of coal seam was researched in micro pe rspective, which provided theoretical basis for high-pressure water injection technology of coal seam in micro perspective. It can be found from nuclear magnetic resona nce experiment that all pore volumes of different pore types of unit volume coal( 1 cm3) increase after high-pressure water injection, the mesopore has the smallest inc rement with the pore volume increasing by 0.73x 10-3cm3 averagely and the small-pore has the biggest increment with the pore volume increasing by 8.79x 10-3cm3 av eragely. Meanwhile, light microscope observation showed that the high pressure water injection was favorable for crack connection, new fractures forming and crack wi dth increasing, so as to increase the permeability of coal for 146% ~ 560%. Based on permeability analysis of the coal, it was concluded that large pore, which was the main methane flow path, was the major control factor of permeability and the secondary control factor was mesopore. The microspore and small pore contribute lttle to permeability and their main effects were adsorption and desorption of methane.

国家科技重大专项资助项目(2011ZX05061)；重庆市国土与房屋管理局科研资助项目(Dyy5095012010016)；