Key Drilling Technology Of ZH-L-03 Coalbed Methane Directional Well In Jincheng Mining Area

With China’s adjustment of industrial structure and the need for green development,clean energy sources such as CBM（coal-bed methane）are increasingly popular.Jincheng Mining Area is an important production area of CBM in China.In order to satisfy the efficient,safe and economic extraction of coalbed methane resources in the area,it is of great significance to research the key technologies in the construction of CBM directional wells.Based on the ZH-L-03 CBM Directional Well Project in Jincheng Mining Area of China Coal Industry and Engineering Group Xi’an Research Institute Co.,Ltd.,this paper optimizes the well layout,wellbore structure and trajectory of the well through theoretical analysis and MATLAB simulation calculation Design;analyze the influence of various factors on the trajectory of the borehole,and further obtain the main factors affecting the stability of the trajectory in the study area;comprehensively study the formation conditions and the similar directional well migration rules to obtain the actual drilling trajectory during the deflection process The occurrence of the hole section was calculated by FLAC 3D numerical simulation to study the stress distribution,displacement vector and displacement cloud map of the stratum encountered,and the impact mechanism of the borehole trajectory was qualitatively evaluated.Based on the analysis of the trajectory control mechanism,the actual The technical conditions for the trajectory control of the sub-well sections were formulated for the construction situation;through theoretical analysis and on-site tests,the influence of the drilling fluid system on the stability of the borehole wall was analyzed,and the formulation and performance parameters were further selected to be suitable for the drilling fluid in the study area.The"straight-increasing-stabilizing"two-dimensional directional well is the best construction well type for coalbed methane extraction in the study area;well locations should be arranged in areas with high gas content and relatively simple structure;when the vertical depth of the deflection point is V₁=617.62m,the slope increase rate Kα=6.88°/30m,and the slope increase angleα=27.92°,at this time,the borehole trajectory is 1808.91m long and the shortest,which can achieve the purpose of optimizing the trajectory.Geological factors and technical factors will lead to a certain degree of deviation of drilling trajectory.As far as the study area is concerned,the soft and hard interbed composed of sandy mudstone and siltstone with a depth of 790m to 860m is the main factor affecting the stability of the borehole trajectory.In the directional tilting section,the drilling process will break the original in-situ stress balance,and the stress concentration area and plastic deformation area will appear in the contact area between the drill bit and the rock.When the drilling tool enters the soft rock,the rock strength of the hard rock is large,To prevent the change of inclination angle,resulting in the deviation of the drilling trajectory;based on the trajectory control mechanism,by optimizing the drilling equipment,drilling tool combination and drilling parameters,the construction can achieve high efficiency and meet design requirements.Various performance parameters of drilling fluid will affect the stability of the borehole wall.The parameters of drilling fluid density,pH value,sand content,viscosity and other parameters can achieve the purpose of efficient,safe and economical directional drilling construction.