The shift towards drilling more complex and challenging wells is continuing in the oil & gas industry. Designing such complex wells with narrow error margins requires advanced well planning tools that account for transient phenomena such as the influx of gas during drilling operations. However, most of the available drilling hydraulics software packages currently do not account for advanced well control modeling options when deploying new drilling techniques such as Managed Pressure Drilling (MPD).
In this paper, we present a novel multi-phase modeling tool that can be deployed in combination with suitable hydraulic models for MPD well control. Its underlying model preserves the transient multi-phase flow behavior of liquid and gas in the well without overly complicating calculation requirements. It is based on coupled conservation equations of mass, momentum, and energy in association with appropriate closure relationships. Several numerical schemes have been utilized to optimize the accuracy and computational efficiency of the software. Furthermore, a user-friendly graphical user interface has been developed for ease of building the simulation cases.
The proposed approach can handle many complexities which occur during a MPD well control incident such as handling multiple influxes from one or several formations, dynamic well control, automated choke control, sudden pump start-up/shut-down, non-Newtonian drilling fluids, arbitrary wellbore path (including directional and horizontal wells), area discontinuity, etc. In addition, this tool can be used to develop and can be used in conjunction with advanced choke control algorithms for MPD. The validity of the software was verified against experimental data from a test well in which a gas kick was induced in a non-Newtonian drilling fluid. The kick was circulated out using the dynamic well control method, which is usually applied during the constant bottom-hole pressure technique of MPD. Parameters such as casing pressure, flow rate in / out of the well, and pit gain were recorded and compared to the simulation results. Excellent agreement was observed between the experimental and simulation results justifying the application of this tool to real-world drilling scenarios.
It will be shown that the new tool can accurately estimate parameters such as maximum casing pressure, annular pressure profile, kick tolerance, flow out, pit gain, gas rising velocity, etc. during MPD operations. Applying advanced numerical schemes makes this tool fast, robust, and efficient. As such, it has the potential to improve well control in general and during MPD operations, thereby enhancing rig safety and reducing non-productive time associated with well control-related trouble events.