Analysis of Drilling Loads in Advanced Casing Design

Abstract

Casing design planning has during the last decades developed from manual calculations performed by the engineer himself, to the use of advanced simulation tools. The tools have become increasingly advanced, allowing the user to perform multiple complex calculations within shorter time. As the software developers allow limited insight into the applied algorithms and calculations it is difficult for the user to verify whether the results are in accordance with the required specifications for the well design. The thesis has evaluated one of the leading well planning simulation tools in terms of functionality, reliability and potential weaknesses. A theoretical study of relevant literature regarding drilling loads has formed the basis for the development of a dedicated calculation model. This model has been used in calculation of specific key loads for casing design in well planning. The results obtained from this model have been compared with the corresponding results of a selected industry leading simulation tool to identify which design theories it is based on and important matters the user should be aware of when applying the tool. Possible improvements have been observed in the way the software communicate with the user and also with respect to the applied algorithms. Some of the algorithms are not updated with the most recent theories and design philosophies and do not take into account the full range of conditions affecting the results. In calculations of buoyancy the forces relevant for well design are not fully implemented. An update is consequently recommended. Temperature effects are particularly important when drilling in high temperate environments. The model applied for calculation of the temperature profile is simplified with respect to both drilling and production loading cases. The program includes safety margins repeatedly in parameters used in the calculations. This imply the well to be over designed in terms of casing planning compared to specified requirements for safety margins. Based on the results of these studies the user is recommended to be critical with respect to the methods applied for the simulation of loads. The elimination of weaknesses in the software may enable more accurate calculations. This introduces possibilities for simplifications of the casing dimensions and accordingly reduces costs without compromising safety.