Viable Options for Managing Thermally Induced Wellhead Movement

Abstract Surface wellhead upward movements may be observed if high temperature fluid stream flows through a well tubing conduit resulting into thermal expansion in the unsupported tubular sections. This is often associated with flowing of high temperature gas injection, high rate high temperature producer or steam injection wells. Initial well design must anticipate these thermal loads and safely manage this movement to prevent damage to well or topside components through optimum pipe specifications, adequate cementing job design and topside flowline movement tolerance to allow predefined magnitude of wellhead movement. Over the well lifecycle, fatigue and degradation could result in increase in unsupported well sections resulting in an amplified thermal load impact. Therefore, periodic surveillance is critical to ensuring thermal loads remain within the safe operating envelope. This paper focuses on non-rig based options to managing wellhead movement to ensure safe well operations on a case study gas injector well A. Options evaluated include lock restraint design/installation, displacement of production annulus to insulating packer fluid and lastly defining a safe movement window. For this case study well A, multistring wellhead movement modelling was done using WELLCATTM. Result of analysis showed that a lock restraint option resulted in significant pipe compression and buckling potentially outside the design envelope. Thermal insulating fluids reduced thermal loads though marginal in this case study due to limited annular clearance. Last option considered was constraining injection temperature to ensure a safe wellhead movement margin that keeps pipe loads within design envelope. Implementing a systematic workflow to manage wellhead movement will enable operators adopt a balanced and fit-for-purpose strategy to minimize safety risk and maximize well service life.