Cuttings Transport Using Pulsed Drilling Fluid in the Horizontal Section of the Slim-Hole: An Experimental and Numerical Simulation Study

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.According to experimental investigations and numerical simulations of cuttings transport, this is subject to a number of variables, including cuttings size, drill pipe rotation, and drill pipe eccentricity. Drill pipe rotation will increase the transport efficiency of cuttings in a horizontal wellbore [14,15]. When the drill pipe eccentricity exceeds a certain value, the height of the cuttings bed increases sharply, resulting in high torque and the possibility of the drill becoming stuck [16]. If the drill pipe rotation speed is too high and the eccentricity is too large, the annulus pressure drop in a horizontal well will increase [17,18], enhancing the resistance and the torque generated in the liquid-solid mixture [19]. Large cuttings size will reduce the transport efficiency and is not conducive to wellbore cleaning [20][21][22][23]. The higher the apparent viscosity of the drilling fluid, the better is the transport performance of the cuttings at low drilling fluid velocities, but the greater is the pressure loss [24][25][26].The conventional method for cuttings transport uses a constant drilling fluid flow rate. 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. To improve transport, a method with pulsed drilling fluid has been proposed. This provides a continuous impact on the cuttings by changing the flow rate of the drilling fluid. Pulsed jet drilling technology can effectively increase the drilling speed [27], and so downhole drilling tools using pulsed jets are equipped with variable-frequency pulse jet generators [28] and spiral pressure intensifiers [29]. Field experiments have shown that the use of pulsed drilling fluid reduces the effect of chipping and increases the effi...

Analysis of Multi-Phase Mixed Slurry Horizontal Section Migration Efficiency in Natural Gas Hydrate Drilling and Production Method Based on Double-Layer Continuous Pipe and Double Gradient Drilling

“…When the flow velocity is large enough, under the influence of fluid-lift and radial pulsation, the exchange of momentum and mass occurs simultaneously among the layers of solid particles. Finally, the solid particles enter the state of suspension and migration, as shown in Figure 4 [16][17][18]. When the DDG method are used, the solid particles such as NGH and sediment are transported in inner pipe of double-layer continuous pipe in the horizontal section.…”

Fundamentals and Physical Principles for Drilled Cuttings Transport—Cuttings Bed Sedimentation and Erosion

“…Effective erosion of the cuttings-bed has major influence on the cleaning efficiency, it has been demonstrated that loose and porous cuttings-beds are easier to clean as single cuttings particles can move freely into the bed, on the other hand, well consolidated cuttings-bed are more complex to clean as the cuttings particles are embedded into the bed and there are not loose particles to move [51]. It has been shown [21,27,55] that to disturb the cuttings at rest and erode the cuttings bed, it is necessary to reach the critical velocity, and it was discussed, that smaller cuttings particles are easier to erode from the cuttings bed.…”

Investigation: Cutting Transport Mechanism in Inclined Well Section under Pulsed Drilling Fluid Action

“…The pulse parameters set under the experimental conditions in th in Table 2 [40]. As shown in Figure 10, with the same q and pulse am…”

“…The pulse parameters set under the experimental conditions in this study are listed in Table 2 [40]. As shown in Figure 10, with the same q and pulse amplitude ratio, the cuttings bed movement distance decreases as the pulse period increases.…”