Numerical Simulation of the Effects of the Helical Angle on the Decaying Swirl Flow of the Hole Cleaning Device

Abstract

The application of the hole cleaning device in downhole is a new technology that can improve the problem of cuttings accumulation in the annulus and improve the hole cleaning effect of the wellbore during drilling. In this paper, the Reynolds Averaged Navier-Stokes model, together with the Realizable k-ε turbulence model, are used to perform transient simulations. The effects of rotational speed, blade shape, and helical angle on the initial swirl intensity and its decay behavior along the flow direction are studied. The swirl number, the initial swirl intensity, the decay rate, the tangential velocity distribution, and the variation of pressure are analyzed. The results indicate that the swirl number of the swirl flow exponentially decays along the flow direction. The straight blade and V-shaped blade have different swirl flow induction mechanisms. Under specific drilling parameters, the critical helical angle is determined for both types of blades. When the selection of the helical angle is close to the critical value, the swirl flow will be close to the axial flow, which is of little help in hole cleaning. Moreover, the rotation direction of swirl flow will change when the helical angle exceeds the critical value.It is widely used in many industries to promote particle transportation by inducing swirl flow in the pipe. Swirl flow is the flow form with velocity components in both axial and tangential directions. It has wide potential in many industrial applications [5][6][7][8]. A variety of methods can be used to enhance the swirling effect of the fluid in the tube, including the spiral wall [9], tangential inlet [10], and blades induction [11,12]. Therefore, the swirl flow can be induced in the annulus by installing a hole cleaning device on the drill pipe, which can effectively improve the hole cleaning effect in the annulus. It is an ideal hole cleaning method, and one of its most significant benefits is that the rotational energy of the blade comes from the drill pipe and no extra energy is needed for the blade.Since the 2000s, a variety of hole cleaning devices have been designed, field tests have been carried out successfully, and satisfactory results have been obtained. Swietlik [13,14] first proposed the design concept of the straight-blade type hole cleaning device and the V-shaped-blade type hole cleaning device. During the process of application, the device can stir the cuttings that were adhered to the wall of the wellbore, so that the deposited cuttings particles can start to migrate again, which can effectively improve the performance of hole cleaning. Rodman et al. [15] reported a blade-type hole cleaning device. Field experiment shows that it can effectively solve the problems of low hole cleaning efficiency and poor wellbore quality. Puymbroeck et al. [16] introduced a compound hole cleaning device with double helix blade small joints. Laboratory experiments and field tests show that the device has an excellent cleaning ability of cuttings bed; besides, it can improve the efficiency of hole cl...

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