Study On Influences Of The Drilling Tools Rotating To Cuttings Removal In Building Inclined Section

The curve section cuttings are easier to deposit to the down sidewall under gravity then form cuttings bed. The cuttings bed existence has brought drilling many safety problems. Those problems include that high friction and torque, bit freezing, pump choking up, adhere sticking, failing to communicate drilling pressure to drill bit, can't explain wells direction change, drilling fluid leaking into the production formations and affect the ultimate recovery, drilling slow even jams borehole to cause borehole scrapped. Consequently, cuttings removal of building inclined section is the key point to ensure drilling security and improve cementing quality.The curve section drilling tools turn to down sidewall because of borehole bending. Drilling tools rotating changes the flow field distribution of annular width gap, increase annular drilling fluid turbulence scale, and make the cuttings in bed surface stir. With the drilling tools rotating direction migration, bring cuttings to high velocity area of annular and increase the probability of the cuttings are carried to wellhead by return drilling fluid. Thus, the study on influences of the drilling tools rotating to cuttings removal in building inclined section has an important meaning for carrying cuttings theory and engineering practice.Analyzing the annulus fluid mechanics in the paper, the circumferential velocity distribution model of annulus flow field considering drillstring rotation was established. The force acting on the cuttings was analyzed by liquid-solid two phase flow theory, According to startup condition and suspension condition of cutting transport The critical startup velocity model of cuttings particles flipping, climbing, slippage and suspension. The influence of drilling tools rotating to cuttings critical startup speed is analyzed. Through calculating, we find that: At 150RPM,the biggest effect rate to the wide annular tolerance is 38%, to the narrow annular tolerance is 47%;at last,in accordance with the critical toggle speed model of rock debris ,with the effect of drill rotating function to rock debris start and migration law at different eccentric annulus,describe the cuttings motion state of different position in annular, and a new method of evaluate borehole cleaning effect is proposed.