This paper provides an overview of an engineering design methodology which uses a tubular design analysis validation software program that provides an analytical method for assessing tubing loads, design integrity, and buckling behavior under complex mechanical, fluid-pressure, and thermal-loading conditions. The design methodology is applied to complex wells (e.g., multizone, multistring completions, and intelligent completions). Tubing load evaluation cases for different operating phases are presented for two complex completion types viz. Intelligent Completion and Mutlizone Dual Completion.

Two (2) well study models are presented for discussion and evaluation of thermal and stress-loading analysis: the first model analyses a dual string completion, and the second model analyses an intelligent well completion. Thermal simulation is first performed followed by tubular stress modeling for tubular selection and design. Well models are focused to present tubing-design integrity analysis for multistring and intelligent completions with various anticipated operating loads during the life of the well. Analysis includes scenarios for simultaneous production/injection, commingled zonal flow control with multiposition interval control valves (ICV), and various other well-operating conditions.

Results show temperature/pressure changes for each simulated load scenario in the modeled wells. Also discussed are the impacts of well-operating temperature and pressure change on tubular axial loading, burst and collapse limitations, pipe movement and buckling potential, and resultant forces on completion packers in a multistring (dual completion) caused by tubular stress loading. Furthermore, tubular thermal and stress analysis is discussed for a multizone commingling intelligent well completion having multiposition ICVs with varying flow/injection rates. Results of thermal and stress modeling are evaluated to select and optimize the well completion design as well as identify well operating limits with respect to a set of combined ICV opening positions during commingled well operations.

Dynamic and complex offshore conditions can cause variations in operating temperatures and pressures in multistring and intelligent well completions in which design margins are slim because of production-casing diameter limitations. A detailed stress-loading analysis aided by thermal- and stress-analysis software provides methods for balancing completion design vs. risk. This process provides savings by optimizing well design to meet design integrity standards without being overdesigned.

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