Hydraulic Parameters Optimization Of Conductor Jetting Technology In Deepwater Drilling

Conductor jetting technology is one of the indispensable technologies for shallow layer drilling in deep water and how to conduct this process safely and efficiently is one of the most concerned problems in engineering.In this paper,the optimization method of the hydraulic parameters such as the displacement,the extension of the bit and the nozzle angle has been studied.This paper proposed the Optimization methods of the displacement,the extension of bit and nozzle angle considering specific factors,like the cuttings carrying capacity,drilling speed meeting the carrying requirements,wellbore stability,hydraulic opening diameter,jetting depth and others.Then,this work established the hydraulic parameters optimization model based on the jetting theory and simulated the jetting process by ABAQUS to study the influence of different factors on the hydraulic opening diameter and jetting depth.At last,the laboratory experiments were adopted to verify the influence law of the displacement,the extension of bit and nozzle angle on the soil mass.The results show that:the volume of broken rock is proportional to the square of the displacement,and the carrying capacity is proportional to the displacement.The relationship between the volume of rock breaking and nozzle angle in unit time is?35?V^1-cos?when other parameters are constant.The data analysis of the experiment and the reference indicates that the calculation model of critical extension value of bit can play a guiding role in the design of the extension of bit.The influence of different variants on the stress field and displacement field of the soil mass has been obtained by the numerical simulation of ABAQUS software and the simulation results show that the distance between the maximum position of the stress field and displacement field and pipe shoe becomes larger with the increase of the extension of bit.Based on the analysis of the velocity and displacement obtained by indoor simulation experiment,method for determining reasonable displacement range has been obtained under the experimental conditions and reasonable displacement range is 6.06L/min⁴2L/min,the reasonable displacement range of 36in pipe is 10.3L/s⁷0L/s?In this paper,the reasonable displacement range is obtained under the study of the target soil layer and experimental conditions.The spot displacement range need to be determined according to the specific soil layer data;?based on the similarity principle.According to the experimental results,the relationship between the speed and the extension of bit was obtained,and there are two significant changes in the velocity,the drilling speed begins to increase rapidly when the extension of bit increase to?35?H₂,while the drilling speed begins to increase slowly until it no longer increases when the extension of bit increases to?35?H₁.The results of numerical simulation and experiment show that nozzle angle has important influence on the drilling speed and optimized nozzle angle is 45°⁶0°taking into account the stability of wellface.