Flow Assurance Study for CO₂ Transport and Injection in Offshore O&G Depleted Reservoirs

A major obstacle to the widespread implementation of carbon capture and storage (CCS) is the efficient transportation of carbon dioxide (CO2). The most economical and secure way to move large volumes of CO2 across long distances is through pipelines. Although CCS technology has advanced to the point of commercial deployment and underground reservoirs are recognized as a secure storage solution, CO2 transportation systems are still a challenging issue and have a lot of operational risks associated with it. For instance, ambient and geometrical conditions surrounding the pipeline can alter the flow of CO2, while proper insulation of the pipeline is also crucial for maintaining CO2 flow and preventing major heat losses. In this context, the current thesis developed a case study that aims to design a complete CO2 injection system and assess the pressure profiles in a CO2 pipeline while monitoring the critical variables influencing transportation, like ambient conditions and pipeline insulation. Specifically, different ambient conditions and pipeline geometries were evaluated to determine their impact on transportation stability, and the minimum insulation thickness necessary to ensure safe CO2 flow was also considered. Regarding the transportation pipeline design, a 16-in pipeline was found suitable to transport CO2 at a mass flow rate of 47 kg/s without exceeding the erosional velocity. The injection tubing was designed to have a 6.6-in diameter to provide sufficient back pressure, and the control valve opening diameter was chosen to be 2.2 in to maintain the required back pressure. These design parameters ensure the safe flow of CO2 for 10 h without phase changes, during which 47 kg/s is injected into the reservoir, as simulated using the OLGA multiphase software package by Schlumberger. The results of the case study showed that the coldest ambient conditions provided the most stable flow, while higher ambient temperatures (30 °C) could introduce two-phase flow risks.