Optimization Analysis Of Downhole Tool In Coiled Tubing Hydraulic Jet Fracturing

Coiled tubing hydraulic jet fracturing technology,as a new type of hydraulic fracturing technology,combines the characteristics of continuous pipe technology and hydraulic jet fracturing technology.It has the advantages of a short operation time,less tripping time,no need for mechanical packing,the ability to accomplish fracturing and hydraulic jet perforation at the same time,and a pipe string can be carried out for multi stage fracturing.Focusing on the downhole tool of the coiled tubing hydraulic jet fracturing process,the whole calculation models of spray nozzle,spray gun,single flow valve and tool string were established in this thesis.Some numerical simulation analyses were carried out for each calculation model,including analyses such as the solid-liquid two-phase flow field analysis,erosion wear analysis,flow characteristics analysis.Research on the optimization for key parameters of hydraulic jet fracturing tool was carried out.A variety of calculation models for the key structural parameters of hydraulic jet ring empty sand fracturing spray gun,such as nozzle diameter,nozzle structure and position distribution were chosen to be optimized using CFD methods.For sand jet,the performance of curve nozzle is better than that of conventional cone nozzle.Nozzle exit diameter is the key parameter that influences the jet flow,the influence on the impact force and the density of the jet is the opposite.Under the premise of satisfying the jet velocity,the outlet diameter should be increased.Meanwhile,the distribution distance of the nozzle on the spray gun is not an important parameter,which has little influence on the performance of the jet.Simulation and analysis of the dynamic characteristics of single flow valve under the reverse circulation was carried out.The relationship between the characteristics of the check valve opening and the flow rate under the reverse circulation,the relationship between the ratio of the nozzle and the flow rate of the valve,and the erosion wear of the check valve were studied.Under the reverse circulation condition,the inlet flow rate and the valve opening degree of the nozzle apply to nonlinear relation.Nozzle flow is smaller,and almost fixed,most of the flow reflux from the reverse flow valve.The internal wear of single flow valve concentrates on the end surface and the inner wall of the valve disc.For the end surface,the flow is increased,and erosion wear is increased,chamfer processing is recommended.The wear of the inner wall and the flow apply to parabolic relation.The conclusions obtained from this study will play an important guiding role in the design and construction for Party A.In particular,the theoretical basis and foundation for the design of a new type of curved nozzle designed by Party A was provided,and a reliable reference for the distance among the nozzles on the spray gun was put forward.According to the preferred displacement range,the wear of the check valve can be greatly reduced,and the service life of the tool can be greatly extended.