Natural Gas Industry B (Aug 2021)
Design and test of a cuttings bed remover for horizontal wells
Abstract
Cuttings accumulation in horizontal drilling of a shale gas well is one of the main reasons for high drilling torque and drag and serious backing pressure and consequently influencing the rate of penetration (ROP), so inhibiting the generation of a cuttings bed and keeping the hole clean is an important prerequisite to ensure the smooth and safe drilling of horizontal section. In order to improve the hole cleaning efficiency of horizontal sections, this paper studied the decay laws of helical flow induced by helix angles and rotation speed of a newly developed cuttings bed remover with V-shaped blades for horizontal wells and their influences on the resuspension distribution of cuttings particles by virtue of the CFD numerical simulation method and Euler–Euler binary-fluid model, combined with the theory of particle dynamics. Then, the parameters such as blade rotation speed and blade helix angle were optimized. And the following research results were obtained. First, with the increase of the rotation speed, cuttings deposit at the bottom of the annulus deflects to a certain degree. And the higher the rotation speed, the more obvious the deflection. Second, annulus pressure drop loss increases with the increase of the helix angle. And this phenomenon is more obvious when the helix angle is larger. Third, the field test results in Well Changning H25-7 of the southern Sichuan Basin show that after the application of the newly developed cuttings bed remover for horizontal wells, the drilling friction is decreased by 33 %, the tripping is smooth without sticking. And in the process of its application, no complex downhole accident happened. Obviously, it provides good hole cleaning to ensure the safe and smooth implementation of the later casing running operation. In conclusion, this newly developed cuttings bed remover can satisfy the demand of cutting bed cleaning and drilling cost reduction and efficiency improvement of horizontal wells, so it is worth popularizing and applying. What's more, it provides guidance and reference for the design of similar cuttings bed removers.
