Optimization of hydraulic jet perforation tools for horizontal wells in broken soft and low permeability coal seams
Aiming at the harm of pulverized coal production in horizontal wells in broken soft and low permeability coal seams,a new concept of hydraulic jet perforation and fracturing was proposed,to enhance coal seam permeability and reduce pulverized coal.The process was comprised hydraulic jet perforation,high-pressure jet,annulus fracturing and hydraulic jet perforation cleaning.Through the comparison of cost and process,drag tubing hydraulic sand blasting perforation fracturing was selected,and the process and key tools were optimized.Firstly,the integrated cemented carbide conical convergent nozzle was optimized to prevent reverse erosion damage,to maintain a jet pressure of 16.5～25.8 MPa when the displacement was 2.0～2.5 m3/min.Secondly,the ejector body was optimized,to effectively shoot through the casing and cement plug,and shoot into the rock to a certain depth.The supporting integrated string successfully completed the construction of 8-stage fracturing and 8-stage supplementary perforation of coalbed methane U-shaped horizontal well.The perforation time of each section was more than 15 min,and fully displaced the backflow pulverized coal.After three years of operation,the gas production is still more than 3500 m3/d,which shows that the optimized process has achieved the transformation effect of broken soft and low permeability coal seams.Compared with coiled tubing staged fracturing technology,the single-stage fracturing operation cost through hydraulic jet fracturing by dragging tubing has been reduced by 28.5%.
broken and soft coal seam with low permeabilityhorizontal wellhydraulic jet perforationfracturing
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