Performance Research And Design Improvements Of Air Hammer Used For Gas Drilling Horizontal Wells

Recent years,oil and gas reservoirs which are large-scale low abundance and difficult to use become more and more numerous.When confronted with these thin layer,multi-layer,dense and strong water sensitivity formations,it is a good solution to drill the reservoir by horizontal wells combined with gas drilling technology which is well protective of reservoir.This technology named gas drilling horizontal wells.When drilling horizontal wells using liquid we usually use positive displacement motor as down hole motors to increase slope lower slope or keep the slope.But the gas drilling technology is lack of such downhole motor,existing PDM motor design based on drilling fluid and conventional air hammer based on vertical design.Both can not be directly applied to gas drilling horizontal wells.Since the 1990s,in order to break this bottleneck.On one hand,domestic and foreign researchers tried to modified PDM motor to the one using air,on the other hand,them tried to modified conventional air hammer to someone can be used for horizontal wells and can used to directional drilling.After a series of studies there was a series of pneumatic PDM motor,however,the principle of PDM motor limited the use of PDM motor's drilling results when useing compressible gas as its driving fluid.Theoretical research and field application have proven that pneumatic PDM motor has the characteristics of small output torque and its rotate speed increased rapidly when the torque decreases.Meanwhile,horizontal well air hammer is also constantly evolving,there are some existing improved air hammer can be used for horizontal wells.But after on-site experiment,these existing horizontal wells air hammer appeared the situation of insufficient torque and easy to stuck.In order to solve the case of poor performance of these existing horizontal wells air hammers,firstly,we established a mathematical model of the working process of the air hammer,programed a mathematical simulation software,carried out air hammer multi-angle experiments,combined bench experiments to verify the accuracy of the mathematical model.Then we use the established simulation software,starting with the analysis of reciprocating mechanism and rotation mechanism,completed the analysis of the causes of performance degradation on the existing horizontal well air hammers.Finally,based on the analysis results,we propose a new type of horizontal well air hammer design.The established downhole air hammer work simulation software can simulate the true state of the downhole air hammer,and the results consistent with bench test results.The established performance measurement for air hammer is convenient and reliable.The proposed new horizontal well air hammer design is optimized based on the results of the studies in this paper,the performance of reciprocating piston vibration mechanism is improved 20%to 30%compared to the previous.And its rotation mechanism can use the time which the rotation torque is zero caused by drilling teeth rebound to rotate the air hammer.