Simulation of Drilled Cuttings Transport through an Inclined Wellbore by Using CFD

Introduction: Efficient transportation of cuttings is a vital factor for optimization of a good drilling operation. This study investigated the influence of a range of variables such as mud weight, cutting size, viscosity and circulation rate on cutting transport efficiency in an inclined well using CFD software. Problem statement: Poor hole cleaning may be responsible for up to 70% of all drilling problems such as: pipe sticking, premature bit wear, slow drilling rate, formation fracturing and high torque and drag consequently extending drilling time and increasing drilling cost. Objectives: The main objectives of this study are: to determine parameters those affecting the transport of drilled cuttings in inclined wells, to simulate a section of annulus with combination of drill pipe and casing to define the variables affecting drill cutting transportation and to develop a graphical correlation between cutting transport ratio to the annular velocity to illustrate the magnitude of the effect of different variables that influence hole cleaning in inclined wells. Approach: Throughout the study, two different methodologies were used which are analytical and simulation methods. In analytical method, two governing equations of motion, Continuity equation and Navier-Stokes equations are derived in accordance to the assumptions made. In simulation method a combination of casing-drill pipe annulus section was simulated and a model called „discrete phase model‟ was used to observe the transportation of cuttings in the annulus section of an inclined (45°) wellbore. Results: the simulation carried out to date had shown that an increase in mud weight slightly enhances cuttings transport as long as there is not an accompanying increase in viscosity, Size of drilled Cuttings the medium-sized cuttings are easier to transport than the smallest or the largest cuttings, the best way to pick up cuttings is with a low viscosity fluid in turbulent flow. And as ROP increases, the hydraulic requirements for effective cuttings transport increases. Conclusion: The main conclusion was that the model predictions exhibit good agreement with laboratory experimental results and observations, for the majority of the case