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Description of the Material This paper describes how the Subsea Safety Critical Systems can be enhanced toprovide greater shearing pressure and volume for the Shear Rams when being usedby the Emergency Disconnect System, EDS, Deadman System, or Autoshear System. Utilizing accumulators which can be charged to 7500 psi differential pressureallows shearing pressures to approach the full working pressure of 5000 psi forthe Shear Ram Operators. Also discussed is the development of the 7500 to 5000psi stepdown regulator and other critical system components and how this systemcan be economically installed on existing Subsea Blowout Preventer (BOP)Systems. Application Some Drilling Contractors presently use 6000 to 7500 psi rated accumulators onthe BOP Stack in order to precharge on the surface to greater than 5000 psi. However, with surface Hydraulic Pressure Units (HPU), rated for 5000 psi, theycannot take advantage of the full working pressure of the accumulators. Thesubsea accumulators can be supplied with 7500 psi by several means. This paperaddresses the use of a hot line or subsea intensifier to supply the fluidpressure to the subsea accumulators. The key to having 7500 psi stored in thesubsea accumulators is to have a 7500 to 5000 psi step down regulator and othercritical components rated for 7500 psi. Results, Observations and Conclusions The 7500 to 5000 psi regulator and critical complimentary control componentshave been designed, developed, and tested for hot line use. The Isolation andDump Sub-Plate Mounted (SPM) valves have been qualified for 7500 psi serviceand the 7500 psi check valves are in the qualification process. The subseaintensifier is under testing and the results will be presented at thepresentation. Significance of Subject Matter The well construction designs for wells presently required by regulatoryrequirements are requiring larger, thicker wall, and higher yield casingstrings as well as drill pipe used in drilling and landing strings. Thesegreater strength requirements are requiring greater shearing pressures for thehigh pressure Shear Rams. Utilizing 7500 psi supply allows shear pressures togo as high as 5000 psi with a reasonable number of accumulators to supply thefluid. Background The goal of a rig's safety critical emergency system is the ability to shearpipe and safely seal the well when circumstances dictate. Two important aspects of Safety Critical BOP Systems are:BOP Components and ArrangementControl System Design, Operating Philosophy and Dedication ofAccumulators
Successful Surface BOP drilling operations from moored semisubmersible drilling rigs of Transocean Sedco Forex Inc. have been progressively developed in deepwater regions offshore Indonesia since 1996. These techniques developed specifically for environmentally benign areas have illustrated significant commercial advantages over traditional methods using subsea BOP and low-pressure riser systems. As a result of these proven potential cost savings, significant effort is being focused on developing of similar Surface BOP and highpressure riser systems suitable for offshore floating drilling applications in more moderate operating environments typical of the Gulf of Mexico, West Africa, Brazil and the Mediterranean.Current industry design guidelines and standards applicable to MODU's are specific to the traditional subsea BOP and lowpressure riser drilling systems. Efforts to develop alternative deepwater Surface BOP technology suitable for moderate environment MODU application have resulted in a requirement for a rational design basis to be established. Development of this technology within the industry is currently fragmented between several groups and an industrycoordinated effort to standardize the design basis and guidelines has yet to evolve.The guidelines presented in this paper evolved from the procedures, equipment, and operational experiences obtained during the successful deepwater Surface BOP drilling operations for the past five years. This experience, combined with various applicable industry deepwater procedures and guidelines is used to develop a methodology to move this technology into moderate operating environments. Further refinements have resulted from HAZOPs, risk analysis and detailed system design along with sound engineering and operational judgement. Implementing the resulting design basis may produce a higher initial capital and operational cost than the benign environment configuration, however, this method achieves or exceeds safety and operational risk factors benchmarked by conventional deepwater drilling operations in moderate environments. The following moderate environment guidelines herein detailed will continue to evolve as the technology advances, but, the established basis of safety to personnel and the environment should remain consistent.
TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractDrilling industry technology is advancing rapidly. Drillers are encountering downhole pressures over 20,000 psi and temperatures over 450°F. These high pressure high temperature (HPHT) conditions require drilling and completion equipment that is beyond the scope of today's API specifications.API specifications 6A 1 , 16A 2 , 16C 3 , and 17D 4 address the design and design verification methods for drilling equipment. These specifications currently reference the ASME Boiler and Pressure Vessel Code, Section VIII, Division 2 5 (ASME VIII-2) as one of the primary design verification methodologies. API specifications first referenced ASME VIII-2 as a design verification methodology nearly 20 years ago, because it was the best available at that time. This is called the "ASME Method".The ASME Section VIII, Division 3 6 (ASME VIII-3) was developed to give the requirements for the construction of high pressure vessels. ASME VIII-3 was first issued in 1997 and is intended to be used in place of ASME VIII-2 for high pressure vessels, generally in excess of 10,000 psi.The design of drilling and completion equipment should be done using first principles. The authors propose that the designs for 15,000 psi or higher service should be verified using the rules from ASME VIII-3. A significant difference between the two design verification methods is that the user specifies the loading criteria for the performance-based ASME VIII-3. ASME VIII-3 requires cyclic load (fatigue or fracture mechanics) analysis and has limitations in materials, fabrication and inspections, and testing requirements that specifically apply to thick-walled pressure vessels. This paper discusses how the performance-based code methods of ASME VIII-3 can be integrated into API specifications for HPHT drilling and completion equipment.
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.
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