A Method for Optimizing Jet-Mill-Bit Hydraulics in Horizontal Drilling

Abstract

Summary Efficient cuttings transport is a major challenge in horizontal drilling; one can use a new type of jet-mill bit to overcome the challenge fundamentally. However, currently, there is no available method for optimizing jet-mill-bit hydraulics, which restricts the jet-mill bit from being widely used. In this paper, on the basis of the high-pressure water-jet comminution and jet-pump theory, a basic performance model of the jet-mill bit is developed. Then, the optimal parameter model for the jet-mill bit is presented according to the multivariable limitation theory; meanwhile, a method for optimizing jet-mill-bit hydraulics is also developed. With the method, one can determine the optimal jet-mill-bit hydraulics. Theoretical analysis and discussion show that the impact angle and the friction-loss coefficient are the key factors affecting the efficiency of the jet-mill bit; the impact angle is suggested to be set at approximately 70 ° and the optimal flow-rate ratio at appoximately 1.0; and the effect of rate of penetration (ROP, m/h) is not obvious, and one can ignore it. The optimal area ratio is almost not related to friction-loss coefficient and ROP, but it is related to the impact angle significantly. It provides drilling engineers a practical tool for determining the optimal jet-mill-bit hydraulics in horizontal drilling and promotes the jet-mill bit to be widely used.