Analysis of drilled wells on the Norwegian Continental Shelf (NCS)

Abstract

Safe drilling operations are a result of integrated geo-mechanical engineering and drillstring mechanical engineering. Torque and drag modeling is used by the oil and gas industry in all phases of drilling a well: Planning, operational and post-operation evaluations. There is an increase in the number of designer wells drilled with complicated wellpaths and extended reach. Good modeling is important to predict the drillstring operational window (ie. buckling or yielding of the drill string) and geo-mechanical well program (i.e collapse and fracture). For this the knowledge of mechanics and hydraulics is important. However, from literature study, and monitoring of real-time data, it is observed that the models do not perfectly capture measured data. Therefore, in order for the model to be reliable, it is important that it is frequently calibrated against high quality real-time field data. A post-run analysis of a drilling operation is useful for determining friction factors and corrections needed to be made to other parameters in order to calibrate the model. When many wells in the same field have been analyzed it is possible to systematically use historic results and data for prediction use and for use in well planning. A post-run analysis of a recently drilled well in the North Sea is presented in detail in the thesis. In order for the results of such an analysis to be reliable, there has to be a systematic process for performing the analysis.