Research And Safety Analysis Of Coal Rock Fracturing In The Near Wellbore Of Coalbed Methane Wells

At the present stage,coal rock fracturing technology has become the main technical measures of coal-bed gas stimulation.With the continuous deepening of domestic and foreign experts,fracturing technology is constantly improving and innovation.According to the characteristics of coal rock Fan Zhuang block,negative pressure reaming technology was used,in which the slotted screens were used for barefoot well completion and the coal rock was fractured by the gas injection pressurization.In this paper,the process parameters of coal rock fracturing were studied,and the whole process was analyzed and evaluated,which can provide theoretical basis for practical work.The mechanism and process of negative pressure reaming technology was first studied in this paper,in this technology,slotted screens were used for barefoot well completion and the coal rock was fractured by the gas injection pressurization,which can cause fracture zone and crack propagation region.Slotted screens play a vital role in the operation of coal rock fracturing,so the stress condition and failure mode of slotted screens were analyzed in the whole process,at the same time,the finite element model was established,and the stress distribution of the screens with different parameters were studied,which can ensure them work safely and effectively.In order to study the effect of coal rock fragmentation,coal rock reservoir-slotted screen three-dimensional finite element model was established using ANSYS software,stress distribution and fracture zone distribution of coal rock under different injection pressure,slot length and hole diameter was studied,in order to determine the optimal construction parameters.In this paper,risk identification and analysis of the whole operation system was carried on,and a risk evaluation index system was established,then the risk factors were quantified by using fuzzy mathematics and expert experience,the weight distribution of the risk factors in the evaluation system were determined using AHP and expert opinion.finally the comprehensive evaluation model of risk assessment was constructed by fuzzy comprehensive evaluation method,and the risk level of coal rock fracturing was obtained by solving the model.Through the safety analysis of the operation process,the risk factors and weak links in the operation can be found out,so as to put forward the corresponding measures to eliminate and control them.