Importance of Thermal/Stress Loading Analysis for Tubulars in HPHT Wells

Abstract

The upstream oil and gas industry is experiencing increased interest in exploration and production from complex, hostile, and deeper geologic horizons that are classified as high-pressure/high-temperature (HPHT) wells. As a result, well completion planning and design has become increasingly more critical and challenging due to uncertainties that might occur during various operational scenarios in the well's lifecycle that could result from high pressure and temperature changes.The cost of typical tubing completion equipment may represent 15 to 25% of the overall well cost. High operating temperatures and pressures can cause the well to operate with significant pipe movement and high axial loads at the packer and tubing. For wells where design margins can be slim, a detailed and robust stress-loading analysis coupled with the aid of modern thermal/stress analytical software provides the opportunity to balance tubular equipment design versus risk. Proper application of this loading analysis can generate significant savings on tubular costs by optimizing the tubing design so that it will meet a company's design standards without being overdesigned.This paper provides an overview of an engineering design methodology that can be followed for tubular equipment sizing and selection for use in complex wells. A typical list of reservoir and well parameters that is required to set up the well model for thermal and stress-loading analysis is presented. The importance of estimated thermal simulation is highlighted for tubular selection and design. Furthermore, a full well casing and tubing design integrity analysis is performed on a complex, high rate, HPHT example well with various anticipated operating loads that include stimulation, production, and enhanced oil recovery (EOR) flooding during the life of the well. Results showing changes in temperature and pressures during well operating scenarios and impact of resultant temperature changes on tubular stress loading are presented. Sensitivity analysis is then performed with applied landing forces on the completion for further discussion on limitations on well operating conditions during the well life cycle.