Lifetime Tubular Design: Combining Effects of Corrosion and Mechanical Wear

Abstract

Abstract During the lifetime of an oil/gas well, wellbore tubular structure might be subject to combined damage caused by both corrosion and mechanical wear. Therefore, it is necessary to conduct detailed stress analyses including these factors at the stage of tubular design. An integrated well construction workflow was established for life-time well design. The temperatures and casing/tubing loads were obtained through numerical simulations of operations such drilling, stimulation, and production. All these simulations were accomplished using commercial software tools, including a thermal flow simulator and stress analyzer. On one hand, a commercial casing-wear simulator was used to predict the cumulative wear amount. On the other hand, a corrosion simulator was employed to predict pipe metal losses during each operation. The total amount of corrosion loss and mechanical loss were then compared against the maximum allowable wear for a safety check of the design. The corrosion simulator was implemented in a computer program and integrated with the aforementioned commercial software of thermal flow and stress analysis. In a plot of maximum allowable wear versus depth, the curves of predicted wear, predicted corrosion, and predicted total metal loss are superimposed with the maximum allowable wear. This plot gives a straightforward and clear picture of the overall lifetime safety of the design. A field case was studied with those integrated simulations. The production casing internal wear and internal/external corrosion were simulated. The predicted wear and corrosion data were in good agreement with the measured results. Further predictions provide rationales for future maintenance/workover operations. Corrosion simulation and casing wear simulation were coupled with wellbore thermal flow analysis and stress analyses, helping proactively prevent tubular failure during the lifetime of the well. It is therefore valuable to include the integrated workflow during the wellbore tubular design where both corrosion and wear are involved.