Trajectory Prediction And Measurement Of Radial Jet Drilling Laterals

Radial jet drilling(RJD)is an unconventional drilling technology to drill multiple radial laterals with a diameter about 50 mm by using high-pressure liquid jet.With the advantages of technically friendly,economically friendly and environmentally friendly,it is a cost-effective alternative to bypass damage zones near the wellbore,re-stimulate the production of old wells and develop the unconventional reservoirs.However,due to the rock breaking method of liquid jet and the process feature of ultra-short turning in casing(90° in 150mm),traditional methods and downhole equipment cannot be applied to predict or measure the lateral trajectory.The unknown trajectory is a crucial limitation to further development and field application of RJD technology.Funded by National Natural Science Foundation,RJD trajectory predicting and measuring method were studied in this paper.Based on the numerical simulation,the influence rules of beddings and joints on rock damage were discussed.The existence of beddings and joints promotes the rock breaking among the updip area and the trajectory deflection to the normal direction of rock interface.The influence of interface can be accumulated.Based on the influence rules,prediction method of RJD trajectory was proposed by regarding the RJD trajectory as a motion trail of vector(transition and rotation).With the reckoned 2D trajectories of jetting vector in vertical plane and horizontal plane of formation obtained by the jetting direction,parameters(position coordinate,inclination and azimuth)of track point can be obtained.Furthermore,according to navigation technology,trajectory measuring method and tools of RJD laterals were developed.The measuring modules of tools of reentrance type and MWD type are respectively smaller than 20 mm and 22 mm in diameter,90 mm and 70 mm in length(including the joint),and more than 3 hours and48 hours continuous working life.The operation temperature of the tools could up to105? and 125?.Except the deterministic error calibration,auto-regressive moving average model?moving Kalman filter and band-pass filter were established to calibrate the random and environmental noise.Based on the process feature of RJD technology,reckoning algorithm and measuring process of RJD trajectory were proposed.Experiments results proved the reliability of measuring method and tools.The average errors of measured lateral length,inclination,azimuth,true vertical depth and horizontal length is 2.17%,1.96%,2.97%,12.24%,3.47% respectively.Results of field tests in Chong Qing proved the feasibility and reliability of the method and tools.Research results fill the gap of RJD trajectory obtaining method,provide the potential and feasible solutions,and contribute to the further applications of directional jet drilling techonology and RJD technology integrated with fracturing.