Formation of Underwater Cuttings Piles in Offshore Drilling

Abstract

Abstract Discharge of drill cuttings to seabed can significantly reduce offshore drilling cost. However, formation of cuttings piles on seabed near the rig site can present problems for drilling and production operations. When the problem is likely to occur in the areas of low current velocity, the cuttings are not discharged to seabed but ground and injected to formation, or transported to onshore for disposal, which increases drilling cost. It is highly desired to have an accurate method to predict the location and configuration of the cuttings piles in the design stage of well drilling. This paper presents a solution to the problem. Starting from Newton's second law of motion, a mathematical model has been developed in this study to predict the location, configuration, and characteristics of cuttings piles. Factors considered include water depth, current velocity, cuttings properties (size distribution, density, and sphericity), and water properties (density and viscosity). This mathematical model has been computerized. It provides well planners a useful tool for predicting the characteristics of cuttings piles during drilling. Application of the tool can reduce cost of drilling through better handling of drill cuttings such as discharging to water versus injecting into formation.