Abstract
Currently available secondary intervention systems may not successfully operate critical subsea blowout preventer (BOP) safety functions such as closing pipe rams, blind rams, and shear rams. Failure may occur because sufficient hydraulic power (pressure times flow rate) is not available to operate these functions quickly in a flowing well, causing failure of sealing elements. This paper describes current shortcomings and identifies a novel ROV-based intervention.
With numerous combinations of rams, bore pressures, bore flows, pipe sizes, and additional equipment inside the well, it is difficult to determine the right amount of hydraulic power required to meet closure times specified by the subsea industry and regulatory groups. This paper considers well conditions and determines the necessary power.
Neither current ROV hydraulic pumping interventions nor hydraulic accumulator interventions can provide the necessary combination of large amounts of flow and pressure for successful secondary operation of BOP safety functions. Also, because current intervention systems are not integrated with ROV systems, they require significant deployment time. Hydraulic accumulator intervention systems provide maximum power at the wrong time—at the beginning of the ram stroke instead of the end—and also have depth limitations.
Given the limitations of current hydraulic intervention systems, an ROV-based intervention system is being developed to reliably operate BOP safety functions. This intervention system, which is integrated with current work-class ROV electrical and hydraulic power functionality, uses novel power management designs.
