Research On Working Mechanism Of Coal Wall Gas Well Wall Supporter

With the decrease of oil and gas, the energy crisis increases. Meanwhile, exploration and development at the coal gas, the shale gas and unconventional gas have become into the hot topic. Studies have been shown that the capacity of coal gas is equal with that of conventional natural gas in our country, whose value of development is important. At present, the horizontal well and multi-branch wells are main methods of developing coal gas. However, there are usual problems that are the drop of drill cuttings, borehole collapse, poor cementing quality and polluting coal on the development.To solve problems above, firstly, the coal sidewall supported device is designed according to similar packer. Secondly, the status of studing about the packer and borehole stability at home and abroad is explained in the paper. A method for determining in-situ stress and fracture criterion of rock are described and the better fracture criterion of rock is selected. Finally, the working process of the sidewall supported device is numerically simulated with finite element method.The main works are following.1. Friction coefficient of surface between rubber and wall was measured under different lubricating conditions.2. The tensile test was studied on the material and the strain-energy function of rubber material was ensured.3. The combined rubber tube was designed and its finite element model was established. The effects of mechanical performance in the process of sealing were analyzed under different main rubber tube lengths, shoulder widths and diameters of sealing strip.4. The analysis model of borehole stability was built and analyzed.The mechanical performance of sidewall supported device was analyzed by the material experiment and numerical simulation. The conclusions are following.1. The axial load and speed have small effect on the friction coefficient, but the lubricating conditions of contact surface have large effect on that.2. With the increase of hardness, the tensile ability, rupture strength, and modulus of elasticity for the rubber also decrease. Poisson's ratio is around 0.48. The mechanical properties of 42CrMo is better than that of 40Cr under 80?.3. With the increase of length, shoulder width and diameter of seal on main rubber tube, the zone of contact pressure increases between rubber and wall. The maximum contact pressure decreases with the increase of length, but it increases with the increase of shoulder width. The axial load has large effect on the process of setting.4. The borehole is stable when hole is located on the roof of coal seam and central on the coal seam, but it is not stable when hole is boundary between the roof of coal seam and coal seam. Under working, the borehole is stable, but it is not stable without working. With the increase of shoulder width and diameter of seal on main rubber tube, the coefficient of borehole stability increases first, then decreases.It act as the reference for the coal actual development of CBM through the research about working principle for the coal sidewall supported device.