Using Continuous Circulation Technology to Improve Drilling Efficiency and Mitigate Downhole Problems

Since drilling of the first oil well over a century ago, fluid circulation must be stopped every time drill pipe connection. Circulation stopping represents one of the main reasons for typical drilling problems related to wellbore pressure. A continuous circulation technology is an innovative drilling method used to maintain the circulation of drilling fluid into the well during making and breaking drill pipe connections. The system contains a manifold connected to drill string that enables safe diversion, and subs installed at the top of each drill pipe stand, providing two independent flows. It can optimize drilling operations and overcome wellbore issues caused by interruption of fluid. This thesis highlights the importance of continuous circulation technology by investigating wellbore issues caused by interruptions of circulation. It showed the advantages of utilizing this technology to improve overall drilling performances in terms of enhanced well control and safety, preventing significant drilling problems from occurring, minimizes annular pressure fluctuations, quality of drilling, saving rig time and reducing drilling operations cost, and improves well production. Potential applications of this technology are also presented, particularly in drilling environments with narrow drilling windows, depleted formations, deep-water wells, extended reach drilling, and high-pressure high-temperature wells. Furthermore, it presents the proposed solutions to mitigate downhole problems in the X- oil field, Iraq, by utilizing the continuous circulation method. The simulations were created based on developing MATLAB codes to make hydraulic calculations and report the wellbore pressure changes that induced by the movement of the drill string for conventional drilling method and continuous circulation system (CCS). The simulation was further implemented for the drill pipe connections scenario to calculate the frictional pressure loss and required pressure to break the gel strength. Moreover, an annular pressure window was simulated for making a comparison between conventional drilling and CCS methods. Results show that downhole pressure variations are significantly reduced, and drilling operations are required a smaller pressure window when using CCS.