Study Of Technology And Key Equipment Design Of Snubbing In CBM Wells

This thesis is combined with the National Science and Technology Project "the study of efficient production technology of CBM wells in Liulin model zone"(NO.2011ZX05062-004)and National Natural Science Foundation(NO.51174224).According to the problems in the workover operation of CBM wells and the demand of CBM reservoir and production technology,the snubbing technology and key equipment for CBM wells was designed,and the production technology and equipment of CBM wells were improved.Based on the analysis of domestic and international status of snubbing technology and equipment used in oilfield and the reservoir characteristic and operation demand of CBM,reasons why the snubbing technology and equipment in oilfield could not be used in CBM wells were given;the snubbing technology of CBM wells was proposed,this technology could finish workover operation rapidly and efficiently without well kill or unloading,which was helpful to the production recovery and high production after operation.After that,the whole scheme of snubbing system of CBM was designed and its operating principle was introduced.The snubbing technology of CBM was designed,the key of this technology was adopting air driven annular blowout preventer to avoid the damage to CBM wells.Meanwhile,the tubing collar could pass the preventer without stop,which was helpful to the improvement of operation efficiency and the recovery of production after operation.In order to meet the demand of operation mentioned above,the structure scheme of air driven annular preventer was proposed innovatively,this preventer used air as the power to control off and on,the compressibility of air allowed the direct pass of tubing collar,which improved the sealing property and efficiency of preventer significantly;the maximum working pressure,drift diameter,working force of rubber core,and the position of balance point were identified;the structure design and check of core components was operated,the calculation results showed the core components of preventer satisfy the operation demand.In order to finish the operation,the hydraulic cylinder of snubbing in system and traveling slip were designed,and the calculation of design and check was operated;based on the demand of hydraulic cylinder and traveling slip,the hydraulic control system was designed.Finally,the CBM snubbing system was consummated,and its working efficiency was assessed based on the technology proposed above.The results showed that the CBM snubbing system can finish the operation in stipulated time,the efficiency can meet the working demand.Without well kill or unloading,the snubbing technology and equipment designed in this paper can finish snubbing operation in CBM wells with the help of workover vehicle.The problems,including reservoir damage,low efficiency and high cost etc.,can be solved,which is of great significance to improve the benefit and commercial production of CBM.