Well Engineering and Injection Regularity in CO₂ Storage Wells

Publication Overview

This project focuses on collecting industry experience on the drilling, completion, regularity and interventions of CO₂ wells. The aim for the report was to compare methodologies and techniques used for handling CO₂ compared with those required for hydrocarbon extraction. This has allowed for a comparison to be made to the research already conducted on CO₂ well integrity and monitoring techniques. The study will investigate whether conditions experienced during CO₂ handling operations were predicted from modelling and experimental work and the effectiveness of linked risk assessments.

Publication Summary

• The aim of this report is to highlight the key differences, and well engineering implications, for handling CO₂ in EOR and deep saline storage locations. These options are compared with conventional oil and gas wells. Best practice for CO₂ operations and the current understanding on handling CO₂ are also covered in detail.
• The ability to inject CO₂ regularly needs to be addressed in the planning stages of storage projects to assess future well performance. For wells exposed to formations containing supercritical CO₂ it is important to identify the procedures and equipment that have to be tailored for the specific characteristics of CO₂ (as opposed to hydrocarbon gas, oil or water).
• Industry experience with CO₂ EOR wells (both for CO₂ continuous injection as well as for CO₂-WAG) shows that new CO₂ injection wells can be suitably designed to allow well integrity to be maintained in the long-term. Concerns from cement degradation and corrosion can be suitably addressed in the design and construction of these wells. Industry experience also indicates that CO₂ storage injection wells can also maintain wellbore integrity if designed, constructed, operated and monitored as per current state-of-the-art design specifications and regulatory requirements.
• Risks from legacy wellbores can also be adequately addressed as long as sound engineering practices and compliance with current and more stringent regulatory requirements are complied with.
• The handling and managing CO₂ wellbore operations safely is well established from CO₂ EOR projects. Initial industry concerns about CO₂ injection, especially during the water alternating-gas (WAG) process in terms of controlling the higher mobility gas; water blocking, corrosion, production concerns, oil recovery, and loss of injectivity have been addressed with careful planning and design along with good management practices.
• Although there are a number of common areas between CO₂ EOR and CO₂ storage wells, the differences can be grouped under five broad categories: (1) operational, (2) objectives and economics, including CO₂ supply, demand and purity, (3) legal and regularity, (4) long-term monitoring requirements, and (5) industry’s experience. There are no specific technological barriers or challenges per se in converting or adapting a pure CO₂ EOR operation into a concurrent or exclusive CO₂ storage operation.
• The costs associated with CO₂ EOR and CO₂ storage projects are site and situation specific. In general, oil prices have by far the larger impact on the economic viability of a CO₂ EOR project, with the second largest impact being the cost of CO₂