Updated Design Methods for HPHT Equipment

Abstract

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.