Determination of the permissible amount of carbon dioxide for placement in a geological structure

Abstract

Relevance. This article presents the results of a study assessing the capacity of geological structures for carbon dioxide (CO2) storage. The target storage formations are the productive reservoirs of depleted hydrocarbon fields. The key objective of the study is to determine the maximum allowable volume of CO2 that ensures secure and safe storage. The placement of CO2 in geological structures is relevant given the trend toward low-carbon energy and the need to reduce greenhouse gas emissions. This issue is related to various aspects: legislative requirements, technology, research, and economics. Underground CO2 placement is recognized as a key technology for reducing atmospheric emissions and is an important component of carbon dioxide capture and storage (CCS) projects. Carbon dioxide disposal projects in geological structures are regulated by international and Russian standards, with specific requirements for the geological conditions and characteristics of CO2-containing reservoirs to ensure long-term safe storage. Injection into depleted oil and/or gas reservoirs–after oil and gas resources have been extracted, these well-studied reservoirs represent the best solution for CO2 storage. Carbon dioxide can be stored in geological structures in gaseous, liquid, and supercritical states. The study of the prospects and risks of CO2 storage in geological structures shows that geological changes (rock movements) can cause carbon dioxide migration from the formation to less sealed rocks and then to the Earth’s surface. Therefore, determining the permissible amount of CO2 for disposal in a geological structure is a pressing issue. The aim of the study is to assess the suitability of geological structures for carbon dioxide (CO2) storage, taking into account various factors, criteria, and regulations. It also examines the criteria for selecting CO2 storage sites, methods for assessing storage potential, the risks associated with gas placement, and methods for calculating the permissible amount of CO2 for placement in a geological structure. Materials and Methods. To determine the permissible amount of CO2 for placement in a geological structure, theoretical methods are used that take into account structure selection criteria, methods such as quantitative assessment of storage potential; calculation of the required volume of CO2 injection; and assessment of the coefficient of gas dissolution in formation water. These methods allow for safe and long-term geological storage of CO2, minimizing risks to the environment, natural resources, and human health. Theoretical-level materials are used, including regulatory documents, calculation methods, rock requirements, and monitoring information. Results. The method – equation is proposed for determining the permissible amount of carbon dioxide for disposal in a geological structure, taking into account the conditions for its long-term safe storage. Several criteria are identified for evaluating potential geological structures for CO2 storage, taking into account changes in the compressibility coefficient of carbon dioxide.