Abstract
Poor transport of cuttings in horizontal sections of small-bore well holes leads to high torque and increases the risk of the drill becoming stuck, reducing its service life and posing a threat to safe operation. Because the conventional cuttings transport method cannot effectively remove the cuttings bed, a transport method using pulsed drilling fluid based on a shunt relay mechanism is proposed. A three-layer numerical simulation model of cuttings transport in horizontal small-bore wells is established. Using both experiments and numerical simulations, the cuttings transport is studied in terms of the moving cuttings velocity, cuttings concentration, and distance of movement of the cuttings bed. By varying the pulsed drilling fluid velocity cycle, amplitude, and duty cycle at the annulus inlet, their effects on cuttings transport are analyzed, and the optimal pulse parameters are determined. The results show that the use of pulsed drilling fluid can effectively enhance the moving cutting velocity and transport distance of the cuttings bed, reduce the cuttings concentration, and improve wellbore cleaning.
Highlights
During the process of drilling a well hole, the differential effect of gravity causes the cuttings to settle more in the lower region of the borehole
The three-layer model considers the instability of the cuttings bed, the rolling and sliding characteristics of the cuttings, and the movement of the cuttings between the suspended layer and the uniform layer than the two-layer model
According to simulations based on the three-layer numerical model, when the height of the cuttings bed in the annulus exceeds a critical value, the movement distance of cuttings bed is reduced to the extent that the cleaning effect in the wellbore cannot reach its desired target
Summary
During the process of drilling a well hole, the differential effect of gravity causes the cuttings to settle more in the lower region of the borehole. According to simulations based on the three-layer numerical model, when the height of the cuttings bed in the annulus exceeds a critical value, the movement distance of cuttings bed is reduced to the extent that the cleaning effect in the wellbore cannot reach its desired target. In this paper, based on a shunt relay mechanism, a three-layer numerical model under pulsed fluid conditions is established Using both experiments and numerical simulations, this paper describes the transport of cuttings in horizontal well sections under pulsed drilling fluid conditions in terms of parameters, including the moving cuttings velocity, the cuttings concentration, and the distance moved by the cuttings bed. In the second section of the paper, based on actual onsite working conditions, a three-layer numerical simulation model of cuttings transport using a pulsed drilling fluid in the horizontal section of a narrow-bore hole is established. With the help of finite element software, the cuttings transport behavior for different values of the pulse parameters is analyzed by numerical simulation, and the optimal values of these parameters are obtained
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