Subsea wells use Annular Pressure Build-up (APB) mitigation devices to ensure well integrity. Type I mitigation techniques control APB by reducing radial heat loss from the production tubing to the wellbore. Type II techniques work by controlling the stiffness (psi/°F) of an annulus by modifying its contents and boundaries. Though the physics of APB mitigation is well understood, the reliability of a mitigation strategy or its interaction with other parts of the wellbore is not always quantifiable. This is partly due to lack of a unified approach to analyze mitigation strategies, and partly due to lack of downhole data after well completion. Simply stated, the engineer is hard pressed to find computational-predictive methods to assess alternative scenarios and strategies within the framework of the design basis during the life of the well. In this light, our paper presents a quantitative approach to design the currently used APB mitigation strategies, i.e., rupture disks, syntactic foams, nitrified spacers, and Vacuum Insulated Tubing (VIT). In each case, the design is linked to the notion of “allowable APB” in an annulus, which in turn, is tied to the design of the casing strings, and thus to wellbore integrity. Based on an extensive survey of published literature and patents, we also review APB mitigation techniques that have been used less frequently or awaiting proof of concept/field trial.

Summary Subsea wells use annular-pressure-buildup (APB) mitigation devices to ensure well integrity. We define mitigation techniques that control APB by reducing lateral heat loss from the production tubing to the wellbore as Type I techniques. Mitigation techniques that control the stiffness (psi/°F) of an annulus by modifying its contents and boundaries are defined as Type II techniques. Although the physics of APB mitigation is well-understood, the reliability of a mitigation strategy or its interaction with other parts of the wellbore is not always quantifiable. This is partly because of the lack of a unified approach to analyze mitigation strategies, and partly because of the lack of downhole data after well completion. Simply stated, the engineer is hard-pressed to find computational-predictive methods to assess alternative scenarios and strategies within the framework of the design basis during the life of the well. In this light, our paper presents a quantitative approach to design the currently used APB mitigation strategies: rupture disks, syntactic foams, nitrified spacers, and vacuum-insulated tubing (VIT). In each case, the design is linked to the notion of “allowable APB” in an annulus, which in turn is tied to the design of the casing strings, and thus to wellbore integrity. We also review APB mitigation techniques that have been used less frequently or are awaiting proof of concept/field trial.

This paper explores a market solution for Operators’ companies to compound their investments in wells, fields, and infrastructure in a low carbon world by applying improved well design, drilling and completion technologies that are adapted to a new generation of geothermal energy production systems. The paper frames challenges posed to the upstream industry by the movement to a low carbon economy, including the climate transition risks related to societal, regulatory, and capital allocation trends. It then examines the technical challenges and solutions related to repurposing oil and gas fields and wells for geothermal energy production and makes high-level recommendations for Operators interested in accessing this new market for geothermal energy - as well as satisfying Environmental, Social and Corporate Governance (ESG) investors.