The Co-Saline Storage Method: Advanced Modeling to Accelerate Offshore CCS
Authors: Kelly Rose , Gabriel Creason, C. , MacKenzie Mark-Moser , Julia Mulhern , Scott Pantaleone , Daniel Tetteh , Lucy Romeo 
Published: May 2024

Abstract
Offshore locations present significant potential for geologic carbon storage (GCS). Key differences and benefits over onshore GCS include locations distal from population centers and abundant, high-quality reservoirs. Yet, offshore GCS projects also face major logistical challenges, such as metocean conditions and more costly operations. Co-saline storage is a proposed concept to defray costs and risks to candidate offshore GCS operations, while leveraging advanced U.S. Department of Energy (DOE), peer-reviewed models to support and expedite implementation.
Assessing for co-saline storage potential involves applying custom GCS risk and resource models to identify and quantify opportunities for safe carbon dioxide (CO2) injection into saline reservoirs while concurrently producing from nearby petroleum reservoirs. Co-saline storage allows for reuse of existing infrastructure, data, and project knowledge associated with hydrocarbon production.
Offshore GCS efforts to date have focused on either enhanced oil recovery (EOR) or dedicated saline storage. This paper shows how the use of artificial intelligence-informed models, optimized for offshore GCS and infrastructure risk evaluation, can identify co-saline storage prospects and offer economic and operational benefits for offshore GCS.
Over the last decade there have been advances in analytical capabilities that combine geo-data science, artificial intelligence, and domain science methods in multi-modeling approaches to improve evaluation and forecasting of risks and resource potential in offshore systems. These peer-reviewed technologies have been integrated into a workflow to assist with identification of locations with existing hydrocarbon production that are suitable candidates for co-saline storage. When used together with commercial data and tools, this geo-data science method can be used by industry and regulators to assess where and potentially how best to configure platforms, wells, and reservoirs to enable CO2 injection into stacked saline reservoirs while producing from existing hydrocarbon plays. This enables strategic reuse of existing infrastructure to defray costs and enable long-term CO2 storage in favorable offshore geologic settings. Ultimately, the co-saline storage approach provides users and stakeholders with data and science-based analyses to inform safe regulatory and operational decisions related to offshore GCS systems.
Decarbonization will require a range of approaches to meet domestic and international climate and operational goals. Existing projects and efforts have focused on single-approach efforts (e.g. EOR, pure saline-storage) to demonstrating the economic and operational viability of offshore GCS. This paper offers a strategic modeling approach for assessing co-saline storage potential (Figure 1). The approach incorporates existing offshore infrastructure and economic benefits from ongoing hydrocarbon production and plays to identify safe and viable GCS locations.
Figure 1 Conceptual diagrams of co-saline storage concept for offshore system. A) Concept for a single borehole implementation, B) shematic of multiple reservoir co-saline injection concept, and C) shows a multi-lateral co-saline concept. Shown are key elements of the co-saline storage model, i) continuing production from existing petroleum reservoir, ii) injection of CO2 into a separate, additional saline reservoir, shown overlying in the diagram, iii) avoidance of key leakage pathways such as faults or pathways, iv) sealing elements such as salt or shale diapers, confining lithofacies bounding saline reservoir, and v) reuse of existing production infrastructure to enable co-saline injection.