Brownfield modifications to convert existing gas production facilities for CCS operations

Abstract

In recent years, traditional oil and gas operators have found novel means of extending the life of their assets and deferring onerous decommissioning costs by converting their facilities from gas production into carbon dioxide (CO₂) injection. While the task of designing for CO₂ may sound simple, CO₂ injection works in counter-intuitive ways, with previously established heuristics derived from years of experience in gas condensate systems being quickly challenged as potentially dangerous. The world of designing CO₂ systems is back-to-front compared with hydrocarbons; it isn’t simply a case of a change in flow direction. Some of the design challenges explored in this paper include: large density variability in CO₂ systems where a small change in the ambient temperature can significantly impact the pressure of a shut-in system; optimal pressure ratings of the vents and drains systems and how previous safety margins may be unsafe; pipeline hydraulic modelling focussed on new areas outside of the traditional suite of analysis, such as assurance of the supercritical phase; understanding liquid water dropout being more of a concern than hydrate formation; injection wells counter-intuitively flowing from low pressure to high pressure; whether to vent CO₂ above or below an offshore platform; and optimal liquefied CO₂ storage vessel conditions and safeguarding.