Field experience has shown that conventional ESP completions can be successfully used in directional wellbores, provided the ESP assembly does not have to pass through regions of high wellbore curvature during installation, and is landed and operated in a relatively straight section of the wellbore. A common "rule-of-thumb" in the industry is that standard ESP assemblies can tolerate up to 3°/100 ft of well curvature during installation without suffering permanent damage. However, if one would adhere strictly to this "rule-of-thumb" guideline, ESP's would be restricted to relatively straight wellbores. Furthermore, the overall curvature of the system and the curvature and stress experienced by each component, are functions of numerous parameters, including the inner diameter, hole angle, azimuth and curvature of the wellbore, and the outer diameter, length, material properties, weight and stiffness of the ESP components. Changes to any of these parameters may have a dramatic impact on the response of the system. Therefore, to be able to consider ESP's for higher curvature wells, more elaborate, reliable method is required to predict localized curvatures, and components were at risk of becoming damaged, and assist in optimizing and making improvements in ESP system designs.

To address this need, a new computer program, ESP-BEND, was developed as part of the first phase of a project initiated by Wood-Group ESP and jointly funded by Wood Group-ESP and C-FER. A series of laboratory tests were conducted on a full-scale ESP assembly to benchmark the theoretical model and to assist in establishing the curvature limits of the components.

To run a simulation in ESP-BEND, the user inputs the directional survey of the well and assembles the ESP system from a database of components. The program determines the trajectory of the wellbore, and locates the region with maximum dogleg. An iterative Finite Element Analysis (FEA) model is used to determine the contact points and forces between the ESP system and the well casing, as well as the curvature, deflection and stress indicators along the length of the system. The results are presented in tabular and graphical format and the user is warned if the calculated parameters have exceeded the set limits.

Contact: Todd Zahacy, Senior Consultant, Exploration & Production

Tel: 780.450.8989 x240