松软低透气性煤层井下水力压裂工艺技术研究

Study on Underground Hydraulic Fracturing Technology for Soft Coal Seam with Low Permeability

为了研究松软低透气性煤层井下水力压裂的施工工艺及技术,以淮南矿业集团潘一矿东井为工程背景,首先根据建立的松软低透气性煤层压裂裂缝尺寸计算模型,分析得出煤体的弹性模量、泊松比是影响压裂裂缝尺寸及决定裂缝形态产状的主要因素;通过分析计算压裂煤体裂缝缝内净压力,研究了压裂泵注压力的影响因素。理论计算得出试验区域煤层起裂压力为24.3 MPa,设计泵注压力30.2 MPa;现场压裂试验与计算压力误差仅为3.3%,证实了理论计算方法的可行性。试验结果表明,水力压裂影响半径达40 m,压裂后煤层透气性及抽采效果大幅提高,瓦斯治理成本大幅降低。

In order to study the underground hydraulic fracturing technology of soft coal seam with low permeability, based on the site conditions of Panyi East Coal Mine of Huainan Mining Group, it was obtained from the analysis that the elastic modulus and Poisson′s ratio of coal were the main factors affecting the fracturing crack size and deciding the crack occurrence form according to the established fracturing crack size calculation model of the soft coal seam with low permeability; and through the analysis and calculation of the net pressure in coal fractures, the affecting factors on the fracturing pump injection pressure were also studied. It was obtained by theoretical calculation that the coal seam' s fracturing initial pressure was 24. 3 MPa in the test area and the designed pump injection pressure was 30. 2 MPa;the pressure error between fracturing test and calculation was only 3. 3%, which confirmed the feasibility of the theoretical calculation method. The field test results showed that the influence radius of hydraulic fracturing was as large as 40 m, and after fracturing the gas permeability of the coal seam and gas drainage effect were significantly improved, and the gas control cost was also greatly reduced.