Research And Application On Surge Pressure For Extended Reach Well

In recent years,Extended reach well is widely used as a kind of economic and effective drilling method in our country.Because of the long layer soak time by drilling fluid,drill string torque and drag impact against the borehole wall seriously,it is a big problem in the process of drilling extended reach well for the wellbore to lose stability.Field drilling shows that wellbore unstability is closely related to the bottom-hole pressure control,most of the wellbore unstability problems occurred during the bottom-hole pressure fluctuation.Therefore,an expansion study on surge pressure state which in the process of drilling extended reach well,setting up prediction model of surge pressure for extended reach well,analyzing the influence factors and giving an available guidance to optimal design of drilling engineering and operation parameters adjusting and optimizing,reducing drilling accidents.This paper studied the difference between extended reach well and conventional well on bottom-hole pressure fluctuation,analyzing the advantages and shortages of steady-state analysis method,proposing an integrated method of using linear regression method,least square method and golden section method together to optimize the rheological mode.Forming a more accurate prediction mode by Herschel-Buckley fluid speed and flow distribution analysis in eccentric annular,in the meanwhile,giving the pressure solution on the basis of Herschel-Buckley rheological mode.Based on theoretical research,fully took most of the influence factors into account including drilling fluid properties,the velocity of drilling string,annular clearance and well depth,calculating and analyzing the influence factors on the basis of closure tube pipe running example,quantitatively described the influence degree of surge pressure on the condition of multiple factors by using principal component analysis and grey relational analysis.Last considering a test well,the author makes the optimization for the rate of tripping out and tripping in,the drilling fluid rheology properties and annular clearance in the field work,recommended reasonable range for borehole stability,which provides a reliable basis for the safety control in field drilling work.