Multiphase Flow Modeling of Surface Equipment in Managed Pressure Drilling Operations

Abstract

Surface equipment for Managed Pressure Drilling operations handles a multiphase mixture of drilling mud, cuttings and reservoir fluid influx. It is mandatory for safe MPD operations that surface equipment be able to handle pressure surges, pressure drops as well as any phase change of the fluid without causing any safety issues. In MPD operations, the surface choke is a key surface manifold component through which the fluid passes before entering the measurement gauges or solids control processing. Depending on choke position and flow conditions, part of the fluid can change phase from liquid to gas as it flows through the chokes resulting in formation of a gaseous phase that can be problematic for the downstream flow measurement devices and equipment integrity. A detailed analysis of the phase transition of the fluid in the surface equipment is necessary that can elucidate design modifications to ensure accurate measurements for safe and efficient drilling operations.In this work, multiphase fluid flow is analyzed numerically using 3-D computational fluid dynamics (CFD) and a 1-D hydraulics network solver to understand the effects of choke positions on the overall pressure drop, pressure surges and onset of phase transformation to ensure surface equipment safety. 1-D hydraulics network results are validated against the 3-D CFD software as well as against experimental studies. Based on extensive numerical 1-D studies, look-up tables and charts were developed that help field personnel design the best surface equipment configuration, determine associated pressure drop and guard against the possibility of phase transformation.