Understanding Drill-Cuttings Transportation in Deviated and Horizontal Wells

Abstract

Abstract Hole cleaning problems are usually encountered at various stages of drilling a well and when not properly managed could results in incidents that may cause oil companies millions of dollars in revenue. There are direct, indirect cost and hidden costs borne by both the oil producing and oil services companies. Efficient cuttings transportation and hole cleaning while drilling are necessary for proper optimization of a drilling operation. In inclined and horizontal drilling, hole cleaning issues are common and complex problems. This paper aims to explore the impact of various drilling parameters and how they affect the required flow velocity and flow rate required for effective cuttings transport and by association the equivalent circulating density. Cuttings transportation is a phenomenon which is a vital consideration of a good drilling program. Ineffective removal of cuttings can result in several problems, such as bit wear, slow drilling rate, increased ECD (which can lead to formation fracturing), high torque, drag, and in the worst case, the drill pipe can get stuck. If not handled properly, this could result in side tracking or complete loss of well. Cuttings transport is controlled by many variables such as well inclination, angle, hole and drill-pipe diameter, rotation speed of drill pipe, drill-pipe eccentricity, rate of penetration, cuttings characteristics like cuttings size and porosity of bed and drilling fluids characteristics like flow rate, fluid velocity, flow regime, mud type and non - Newtonian mud rheology. The key factors for optimizing hole cleaning are a good well plan, the right drilling fluid properties, and good drilling experience. The direct benefit of this paper is that it facilitates the detection of potential stuck pipe situations and directs the interception of these incidents before they occur. To further aid the users of these principles, there is a chart specifically designed to enable field personnel estimate the possibility of problematic equivalent circulating density and avoid getting stuck using the well parameters available to them before running in hole with the bottom hole assembly to determine the stuck-probability and mitigation methods. The field personnel is offered an opportunity to avoid hole cleaning challenges and potential stuck pipe problems before they occur. We are therefore able to review the drilling program with the information deduced from the chart to be sure all findings have been taken into consideration before drilling commences.