Modelling and estimation for return mud flow during drilling

Abstract

Oil drilling is performed to retrieve gas and petroleum from reservoirs that can be kilometers down the earth surface. During a drilling operation, drilling fluid is pumped into the well to remove cuttings and maintain a stable pressure. A multitude of models that describe the dynamics of the drill fluid through the bottom side of the drilling operation have been developed through the years. However, there is a lack of models that describe the topside flow loop. This is the case since the flow of mud through the return line has traditionally been directly measured using paddle and Coriolis meters. With an increase in demand of accuracy and an interest to avoid the use of Coriolis meters to reduce costs, the interest in alternative ways to describe the drill fluid circulation through the system has increase. One of which is with the use of mathematical models. In this project, a model for the drain back to the active pit was developed and tested for various operational scenarios as well as giving description for the different parts of the topside flow loop. In addition to this, model based estimation of flow using a Venturi channel was tested and compared with the traditional method using Bernoulli’s equation, as this can be an alternative way to measure the discharge from a return line. The results of the comparison were similar using the experimental data available.