Managed Pressure Drilling (MPD)
addresses a multitude of technical problems encountered in carbonate reservoirs of numerous oil fields. The solid cuttings transport flowrate, stability and cost of cuttings transport from the carbonate rock formation towards the surface must be monitored accurately, because drilling safety and efficiency is of paramount importance. A profound understanding of the effect of the geometry and rheology on the pressure profile along the wellbore is essential, so appropriate rheological models (Rooki et al., 2012) of the drilling fluids (derived from viscometric studies) must be used toward technically relevant and numerically reliable CFD modeling studies.
Drilling fluids perform several simultaneous tasks during MPD, offering hydrostatic pressure, cooling the bit, transporting cuttings to surface, maintaining wellbore stability and preventing contamination of the formation. Thus, they must possess acceptable stability in terms of density and rheology over a range of external conditions. Industrial demand is trending towards advanced drilling fluids with tailor-made properties, which can alleviate problems as they arise. Current high-performance requirements foster the development of smart drilling fluids, which are stable at downhole conditions, can perform the required tasks and have a much lower environmental footprint.
Computational Fluid Dynamics (CFD) modeling of cuttings transport during MPD drilling operations can potentially have a strong impact on exploring numerically the attainable envelope of MPD drilling operations, and it has been attempted in very few cases (Nakagawa et al., 1999; Li & Kuru, 2003; Rooki et al., 2013). Research studies for gas-solid-liquid flows (the fundamental cuttings transport mechanism) have been published in the past, but most are not concerned with the elucidation of flow patterns and cuttings distributions, particularly for smart drilling fluids. Modern commercial and/or open-source CFD codes can tackle these problems successfully, yielding detailed state variable (pressure, slip velocity, solids loading) profiles as a function of drilling configuration and pipe position. This paper aims to present relevant case studies for non-Newtonian (e.g. Herschel-Bulkley) drilling fluids, which can be very efficient in MPD implementations.
1. Li, Y., Kuru E., Numerical modeling of cuttings transport with foam in horizontal wells, Journal of Canadian Petroleum Technology 42: 54-61 (2003).
2. Nakagawa E.Y., Silva V., Boas M.B.V., Silva P.R.C., Shayegi S., Comparison of aerated fluids/foam drilling hydraulics simulators against field data, SPE Paper 54319 presented at the SPE Asia Pacific Oil and Gas Conference and Exhibition, Jakarta, Indonesia (1999).
3. Rooki, R., Doulati Ardejani, F., Moradzadeh, A., Mirzaei, H., Kelessidis, V.C., Maglione, R., Nourozi, M., Optimal determination of rheological parameters for Herschel–Bulkley drilling fluids using genetic algorithms, Korea Australia Rheology Journal 24: 163-170 (2012).
4. Rooki, R., Doulati Ardejani, F., Moradzadeh, A., Norouzi, M., Simulation of cuttings transport with foam in deviated wellbores using computational fluid dynamics, Journal of Petroleum Exploration & Production Technology 3(3): 1-11 (2013).