Simplified Hydraulics Model Used for Intelligent Estimation of Downhole Pressure for a Managed-Pressure-Drilling Control System

Abstract

An essential part of an automated managed-pressure-drilling (MPD) control system is the hydraulics model, which, in many cases, is the limiting factor for achievable accuracy of the system. Much effort, therefore, has been put into developing advanced hydraulics models that capture all aspects of the drilling-fluid hydraulics. However, a main drawback is the resulting complexity of these models, which require expert knowledge to set up and calibrate, making it a high-end solution.In practice, much of the complexity does not contribute to improvement of the overall accuracy of the pressure estimate simply because conditions in the well change during MPD operations and there are not enough measurements to keep all of the parameters of an advanced model calibrated.We will demonstrate that a simplified hydraulics model based on basic fluid dynamics is able to capture the dominating hydraulics of an MPD system. Furthermore, we will demonstrate that, by applying algorithms for online parameter estimation similar to those used in advanced control systems in the automotive and aerospace industry, the model can be calibrated automatically by use of existing measurements to achieve a level of accuracy comparable with that of a calibrated advanced hydraulics model. The results are demonstrated using field data from MPD operations in the North Sea and dedicated experiments obtained at a full-scale drilling rig in Stavanger.

Fault diagnosis of downhole drilling incidents using adaptive observers and statistical change detection

“…The process model [29] is a simplified hydraulics single-phase model with two control volumes connected with a momentum balance at the drilling bit. This model has been verified for offshore MPD commissioning tests, and is suitable for control and detection purposes where unknown parameters can be estimated.…”

Early Pack-Off Diagnosis in Drilling Using an Adaptive Observer and Statistical Change Detection

“…The model is a simplified hydraulics model (Kaasa et al, 2012) for managed pressure drilling, given by dp…”

Design and Comparison of Constrained MPC With PID Controller for Heave Disturbance Attenuation in Offshore Managed Pressure Drilling Systems

“… Effective bulk modulus. A bulk modulus is used because the degree of mechanical compliance of casing, pipe, hoses, and other components is uncertain and also it is impossible to predict the amount of gas pockets, bubbles, or breathing of the well (Kaasa et al (2012)). …”

“…There are several studies about different aspects of MPD modeling (e.g. see Landet et al (2012aLandet et al ( , 2013; Petersen et al (2008); Mahdianfar et al (2013); Kaasa et al (2012)). Estimation and control design in MPD has been investigated by several researchers (e.g.…”

“…Estimation and control design in MPD has been investigated by several researchers (e.g. see Kaasa et al(2012); Nygaard et al (2007c); Breyholtz et al (2010); ; Zhou and Nygaard (2011); Godhavn et al (2011)). These studies are mainly focused on pressure control during drilling from a fixed platform without any heave motion.…”