基于RFPA数值模拟的煤层水力压裂技术研究

Study on hydraulic fracturing technology of coal seam based on RFPA numerical simulation

瓦斯灾害严重制约着煤炭工业的发展,为了保障煤矿安全生产,利用水力压裂技术对煤层瓦斯进行抽排。采用理论分析与RFPA数值模拟的研究方法,研究了不同侧应力系数对水力压裂的拓展规律以及裂纹拓展长度分析。研究得出:当λ<1时(垂直地应力大于水平地应力),裂隙的拓展方向为垂直方向;当λ=1时(垂直地应力与水平地应力相近),裂隙的拓展方向杂乱无章;当λ>1时(垂直地应力小于水平地应力),裂隙的拓展方向为水平方向;随着地应力差值的逐渐增大,起裂压力逐渐变小,因此可以提前对压裂钻孔进行预处理,使得钻孔应力重新分布,来达到降低起裂压力的目的。

Gas disaster severely restricts the development of the coal industry,in order to ensure the safe production of coal mines,hydraulic fracturing technology was adopted to extract gas from coal seams.The theoretical analysis and RFPA numerical simulation method were used to study the law of expansion of hydraulic fracturing with different lateral stress coefficients and the analysis of crack propagation length.The study found that: When λ < 1( vertical stress is greater than horizontal stress),the direction of development of fissure is horizontal vertical; When λ = 1( the vertical stress is close to the horizontal ground stress),the direction of fracture development is chaotic; When λ > 1( vertical stress is less than horizontal ground stress),the direction of development of fissure is horizontal; With the gradual increase of ground stress,the initiation pressure gradually becomes smaller,so it can pre-treatment of fractured boreholes is carried out in advance so that the stress of the borehole is redistributed to achieve the purpose of reducing the initiation pressure.