The Fundamental Characteristics on Particle Size Distribution of Drilling Rock-Cuttings

Abstract

The properties of particle size distribution of rock cuttings and its shape characteristics are the most important parameters to petroleum drilling engineering. The samples of rock drill-cuttings are collected from 7 wells within the depths of 3500 m in Liaohe Oilfield of China. The particle size distribution laws of these rock samples with the average diameter over 74 μm are analyzed. The result shows that the drill cuttings feature obvious sheet shape and the size distribution curve of the particles is mainly related to the formation rocks and drilling bits. While drilling at the well depths of between 0 and 2000m by the cone bits, particle size distribution of drill cuttings has a form of approximately power function, the probability particle diameter being 8.50～9.27 mm. Drilling at the depths of between 2000 and 2800 m by the cone bits, the size distribution of cuttings has a form of nearly function, the probability particle diameter being 3.04～4.67 mm. Drilling at the depths under 2800m by PDC bits, the size distribution has a form of nearly the Rayleigh distribution, the probability rock diameter being 0.91～0.94 mm.