Hydraulic Drag Reducing And Hydraulic Parameter Optimization Of Window Radial Horizontal Drilling Technology

The window radial drilling technology is a typical application of water jets to enhance the oil production,especially effective for reservoirs with low porosity and low permeability.Unlike conventional method,this new technology uses hydraulic power to penetrate through the formation and the drill string is generally small-diameter coiled tubing and high-pressure hose.Thus,a large amount of hydraulic power is wasted when the drilling fluid is flowing through the pipe because of the high flow resistance.This will cut down the hydraulic power out of the drilling bit.The equipment costs will rise substantially to increase the surface pump pressure so that the drilling bit can get enough hydraulic power.To address this problem,this paper proposes a method to reduce the hydraulic power loss along the drill string by adding drag reducer into the drilling fluid.Firstly,the normally used high pressure hose with inner diameter of 8mm is taken as the subject for study on the basis of the analysis of drag reduction mechanism of different kinds of drag reducers.The numerical simulation method is used to study the relationship between the hydraulic power loss along the path and the length of hose,swept volume and fluid viscosity.The results indicate that compared with pure water,viscoelastic fluid can greatly reduce the hydraulic energy loss.When the discharge volume is 60L/min and the fluid viscosity of 13.5cp,it has the hydraulic power loss along the path and drag reduction efficiency is up to 51.4%.This work provides a foundation for laboratory test of the optimization of drag reduction agent.Secondly,according to the theory analysis and numerical simulation results,four kinds of drag reduction agents are preliminary selected: polyacrylamide(PAM),poly ethylene oxide(PEO),the Gemini viscoelastic quaternary ammonium surfactant and the extreme pressure lubricant HY-202.Hydraulic energy loss along the path is tested with inner diameter of 8mm and 16 mm nylon hose and diameter of 14.6mm coiled tubing under different concentration of reduction agents and discharge conditions.The results are compared to the fluid of pure water under the same conditions,which shows that the power losses of fluid with the reduction agents are all lower than the pure water.In addition,when concentration of the surfactant drag reducing agent Gemini viscoelastic quaternary ammonium surfactant is 1.5%,not only the drag reduction rate can reach 64.49%,at the same time it shows better anti shear performance.This is the ideal reduction agent to be used in radial drilling operation.Finally,the optimization design of hydraulic parameters in the new radial drilling technology is conducted and computation program is compiled to calculate the hydraulic power loss along the path.It can provide a reference for the field application.