Study and analysis on coal structure features during drilling operation and well wall stability

in order to study the cal stoucture features aifected to the stablity of the wll ore in seam,based on the GSl quantzed coal structure in combination with the sit logging information,with he regressive analysis on the principle compostion.the space ditoibuted mutiple egressions model of the coal structue was establshed.Acording to the Hoek-Brown strengh theory.based on the CSl uantiativ featues of the coal structure a new evaleation methodof the well all eailly in seam was proided. Eased on the rlling in Shihuang Suth Block of Qirshui Basin as a case,the pressure of the sean well ll olpsed was caculated.The resuits showed with the appliction of the method,the fiting between the well all cllapsed pressure and well diameter cure was 75 % and the evaluation results were relable.The more broken of the cal structure the higher cllapsed pressure of th wel all would be and thepoor sablityofthe we all .ould be.The dcominan cal structurewould be the major control factor of the single well wall stability.