Surface Facility Concept Selection for Optimal Carbon Dioxide Injection Using Integrated Modeling Approach

In 2020, the International Energy Agency identified that carbon capture and storage (CCS) is a must to reach net-zero emissions. Multiple players in the exploration and production industry are currently evaluating the possibility of converting oil and gas assets into CCS systems. For example, Gassnova studied a flexible CCS chain which uses carbon dioxide (CO2) ships to transport CO2 from multiple sources to a single storage hub in 2016. In their study, they investigated technical feasibility for three different boosting options and three different tank pressures (low, medium, and high) of CO2 ships. This study focuses on a CCS system that utilizes liquefied CO2 carriers using low tank pressure to transport one million tons of CO2 to an onshore processing facility annually. Since the collected CO2 features a very low temperature (-50 ºC) and low pressure (7 bara), CO2 should be heated and compressed to meet required pipeline inlet conditions. This study proposes three different boosting concepts (liquid, gas, and liquid-gas) for its onshore process facility. To evaluate the proposed concepts, an integrated modeling approach is used in this study. The integrated asset modeling approach couples subsurface and surface models to consider interactions between each condition. This approach has proven that an integrated model provides a more precise representation of the oil and gas production systems, compared to studying the asset independently in standalone subsurface or surface models. A concept selection study of CCS systems can also benefit from this integrated modeling approach via rigorous modeling of the injection system from a CO2 source to the storage site. In this report, an integrated model from the surface injection facility to CO2 injection wells is developed to rigorously evaluate three distinct boosting concepts. Under the given conditions, the liquid concept is identified as the most energy-efficient option for the CCS system in this study. A key finding is that heat exchangers are major contributors to total energy consumption, underscoring the importance of heating over pressure boosting. Following the selection of the optimal boosting option, an optimization study is conducted using the developed integrated model to minimize the energy consumption of the onshore facility throughout the entire injection period. The outlet temperature of onshore facility is sensitized at different lifetimes to ensure optimal operating conditions while ensuring the dense phase flow in the CO2 transportation system. The optimization study reveals that lowering the discharge temperature of the surface injection facility, particularly to 15 ºC in the late life scenario, can reduce energy consumption by 33%. This highlights the potential for optimizing operational conditions to improve system efficiency while meeting design criteria. Simulation results in this study prove that the integrated model can be used to optimize the design and operation of a CO2 injection facility rigorously by calculating CO2 flow hydraulics in CO2 pipelines and the CO2 injection characteristics of reservoirs. The integrated model also demonstrates that it reduces effort days for modeling work as the required facility outlet pressure is updated and it is passed automatically to the facility model whenever operating condition is changed. This eliminates the necessity of manual model update and human error.