New Generation Control System for 20 KSI Subsea BOP

Abstract

Description of the Material This paper describes the reasoning and methods used to design, develop, andtest a 7500 psi differential pressure Subsea BOP Control System. This systemintroduces the necessary upgrades and enhancements to existing control systemsfor application on the very demanding 20,000 psi Subsea Ram BOP Stacks. ManyDrilling Contractors are requiring additional features on 20 ksi BOP Systemssuch as additional Ram Cavities and larger Shear Ram Operators which requiresignificant additional control fluid at higher pressure. The 7500 psi controlfluid supply requires fewer accumulators and delivers greater usable fluid thanconventional 5000 psi systems. Application The BOP Control System is enhanced to supply 7500 psi differential pressurefrom the surface supply to the accumulators on the Lower BOP Stack. The surfacehydraulic power unit, HPU, and accumulators supply the diverter and othersurface requirements and supplies the subsea BOP through the riser conduit(s)and hot line. The rigid conduit manifold distributes the 7500 psi hydraulicsupply between the LMRP accumulators, redundant pods, and lower BOPaccumulators. 7500 psi to 5000 psi step down regulators supply fluid to podmanifolds and Lower BOP Stack functions. Results, Observations and Conclusions Development of the key components of the 7500 psi system include, surface HPU, various sizes of regulators, SPM function valves, check valves, shuttle valves, and isolation valves. Development of these components has proven the newGeneration of 7500 psi BOP Control System is a viable solution for the newgeneration of 20,000 psi (20 ksi) BOP Systems. Significance of Subject Matter The 7500 psi control system supply allows Emergency Systems such as the Casingand Blind Shear Rams capable of shearing pipe at demands approaching 5000 psiwhich would be prohibited by 5000 psi systems. The 7500 psi Control Systemgreatly reduces the number of accumulators needed for surface and subsea highpressure control fluid storage when compared to 5000 psi control systems. Background The industry has been drilling high pressure and high temperature (HPHT) wellson the shelf and in deepwater Gulf of Mexico (GoM) to true vertical depths ofover 30,000 feet over the last decade. The reservoir pressures exceed20,000–25,000 psi and temperatures can exceed 300°F. The mudline shut-inpressures for some of these wells approach, and in some cases exceed 15,000psi. To date, deepwater Mobil Offshore Drilling Units (MODU's) have not had thewell pressure containment equipment to complete wells where the anticipatedwellhead pressures approach or exceed 15,000 psi.