Patent ID: 8459285
Filing Date: 2013-06-11
Classification: E21B,F17D,G05D,Y10T

Abstract:
1. A method of mitigating slug formation in a multiphase fluid stream that is flowing through a conduit wherein the conduit comprises a first portion and a second portion which is upwardly inclined to the first portion and wherein the multiphase fluid stream comprises a gaseous phase and a liquid phase, the method comprising the steps of: (a) determining the pressure in the conduit upstream of a slugging zone; (b) determining the pressure in the conduit downstream of the slugging zone; (c) determining the actual pressure difference across the slugging zone by subtracting the downstream pressure from step (b) from the upstream pressure from step (a); (d) optionally, subtracting the frictional pressure drop across the slugging zone to obtain a value for the true hydrostatic head within the slugging zone; (e) using the actual pressure difference or the true hydrostatic head to determine the liquid hold-up or mixture density within the slugging zone; (f) determining the error between a target pressure difference and the actual pressure difference or between a target true hydrostatic head and the actual true hydrostatic head or between a target liquid hold-up and the actual liquid hold-up or between a target mixture density and the actual mixture density; (g) producing a signal comprising a first component which is proportional to the error and a second component which is proportional to the rate of change of the error over time; and (h) using the signal produced in step (g) to control the position of an adjustable choke valve located downstream of the slugging zone so as to stabilize variations arising in the actual pressure difference, actual true hydrostatic head, actual liquid hold-up or actual mixture density over time.