Numerical Simulation of Downhole Particle Flow in Horizontal Well with PDC Bit

In the deep shale gas horizontal well drilling, the low cutting carrying efficiency often lead to the problem of bit ball. To address the problem, the CFD-DEM coupling method is used to simulate the horizontal well flow field between PDC bit and bottomhole. The cutting movements in the bottomhole flow field under different conditions are studied. It is proposed to evaluate the cutting carrying performance of the flow field between PDC bit and bottomhole by using the cutting retention volume and cutting carrying ratio. The results show that in the bottomhole near PDC bit, smaller drilling fluid flow rate results in greater cutting channeling in the core area of PDC bit. The channeling of drilling fluid is mainly related to the hydraulic structure of the drill bit, but has nothing to do with the flow rate. In the annular, smaller drilling fluid flow rate leads to more dominant gravity effect. Gravity is the main factor of cutting bed forming at the bottomhole. The force by the rotating body can bring the cuttings from the low velocity flow layer to the high velocity flow layer, thus gives the cuttings the axial movement energy, which was carried to the wellhead with high-velocity drilling fluid. The drilling fluid flow rate and rotation will affect the cutting retention volume and cuttings carrying ratio. The study results can provide references for the study of cutting carrying near PDC bit in horizontal wells.