The 15,OOO-psi BOP System for Floating Drilling

ABSTRACT Fifteen thousand PSI subsea drilling equipment is becoming a reality on a significant number of offshore floating drilling vessels. The earliest application used 11 inch and 13-5/8 inch bore BOP systems. However, the new emphasis has been placed on 18-3/4 inch systems and each of the various manufacturing suppliers is in various stages of design, manufacturing and testing. This application of extending present technology should not be taken lightly; rather the offshore industry should be concerned with the application and extend to the equipment manufacturers any pertinent information which will enhance the design and field application of the product. It has become obvious from SEDCO's experience with 15,000 PSI several areas of the system must be investigated and, in some cases, design changes made. These areas include :Methods of sealing components which are attached together and subjected to large bending moments such as ram presenters clamped to wellhead connectors and choke/kill valves clamped to BOP body outlets.Annular BOP requirements for 15,000 PSI ram presenters.Upper and, lower BOP frames and their interface.Choke/kill lines and their attachment to the riser.Surface choke/kill manifolds, especially the valve/choke arrangements and their operation. This paper will detail areas which should be of concern to the offshore industry relating to 15,000 PSI subsea drilling equipment and how SEDCO and the drilling industry have been working with various vendors to eliminate potential problems. INTRODUCTION The use of 15,000 PSI BOP Systems is becoming more common around the world, however, the percentage of 15 KSI subsea systems remains very low. This paper will address the subsea system used for a floating drilling vessel using 15,000 PSI Blowout Prevention equipment. The components to be discussed are shown in Figure 1, Figure 2 and Figure 3. This paper is not intended to be a guideline for 15 KSI subsea systems, rather, the information contained here has been accumulated from the result of work associated with upgrading or new construction of seven (7) 15,000 PSI systems in the past 18 months. Fifteen thousand PSI requirements extend beyond the equipment required to close in the pressure at the wellhead. If a well control situation should occur the choke/kill lines which bring the pressure to the surface to the choke/kill manifold have to be capable of handling the pressures while flowing liquid/gas. This will require special review of existing well control techniques to establish proper procedures for working in a well control situation with high pressure. Additionally, the design of casing strings to contain 15,000 PSI is of primary importance when planning a well where high pressure is expected. This paper will address only those components required to close in high pressure at the wellhead and the pressure containment equipment required to flow well bore fluids to the surface choke/kill manifold. Blowout Prevention Systems rated for 15, 000 PSI or greater have been used throughout the world for over 15 years. However, only a few of these in number have been adapted to subsea use. The present 15 KSI systems used for subsea applications are either 13-5/8 inch bore, 1.1 inch bore or smaller.