Introducing and Defining Riser Gas Tolerance

Abstract The presence of gas in deepwater marine risers poses significant risks. Introduction of RGH/MPD equipment, along with improved understanding of riser gas behavior, has led to a reconsideration of methods to mitigate such risks. Using conventional diverter practices, any sizeable amount of gas in the riser cannot be considered tolerable, given the need to protect the rig and the environment. The use of RGH/MPD equipment allows for safe handling of significant quantities of gas in the riser. Riser Gas Tolerance (RGT) quantifies such ability. RGT emphasizes controlled, pre-planned responses to manageable gas events, minimizing reliance on emergency discharges and diverters, which have shown limitations and environmental downsides. Implementing Riser Gas Handling (RGH) capabilities requires equipment that includes riser top seals, flow outlets equipped with a choke for pressure control, and mud-gas separators. With simplified calculation of surface pressures caused by gas migration using principles, worst-case scenarios can be estimated and pressures managed effectively within the existing RGH equipment limits. This methodology supports standardized planning. The IADC provides tools, such as an RGT worksheet, to facilitate calculations and integrate RGT into risk management processes. The adoption of RGH systems enhances the industry's ability to tolerate and safely manage riser gas events while reducing environmental and operational risks.