Upper Marine Riser Package

Abstract

ABSTRACT A new integrated riser tensioning system is presented. The system unitizes upper riser components into a compact package, and uses the slip joint as the support structure for the riser tensioning cylinders. The system is called the Upper Marine Riser Package (UMRP). The system components, advantages, and potential applications are discussed. INTRODUCTION In offshore drilling operations, the riser system is the communicating link between the vessel and the subsea wellhead. The riser has very little inherent structural stability. Its ability to resist environmental loading is derived from applied tension. Conventionally, riser tension is maintained through tensioners that are connected by wire rope over sheaves to a tensioning ring (Figure 1). The tensioning ring bears against .a hub on the top of the slip joint outer barrel. The flexibility of the wire rope minimizes the effects of yaw that would otherwise be transmitted to the riser. The slip joint compensates for the heave of the vessel; its inner barrel moves in and out of its outer barrel. It is attached to the vessel usually by a flexible joint. The conventional system features a load path from the tensioner framework/derrick through wire ropes, over sheaves attached to the substructure, to the slip joint tensioning ring. The Upper Marine Riser Package (UMRP) is a new integrated riser tensioning system that uses the slip joint as the support structure for the riser tensioning cylinders (Figure 2). The UMRP is the unitized upper portion of the riser string, including the riser tensioners. The load path of this system starts at the self-tensioning slip joint, and is transferred to the rig substructure through the upper flex joint and the diverter assembly. THE UMRP SYSTEM The UMRP includes the diverter assembly, upper flex joint, self-tensioning slip joint, and riser rotation bearing joint (Figure 3). The major component of the system is the modular self-tensioning slip joint. It consists of an arrangement of hydraulic cylinders mounted around a standard slip joint. The lower end of the self-tensioning slip joint is attached to the riser with a riser rotation bearing joint, and its upper end is flanged to the upper flex joint. The flow diverter which is connected to the top of the flex joint completes the package. The UMRP design accomplishes the following objectives:Saves space on the vesselEliminates sheaves and wirelines typical of traditional riser tensioner systemsDepending on the vessel, the UMRP can lower the vessel?s center of gravitySimplifies running the slip joint, and establishing the riser tensionersProvides for faster and safer riser system deployment The system weighs less than a conventional tensioner system with a comparable tension capacity. The UMRP has been designed for a maximum of 1.5 million lbs. tension at 3000 psi pressure, and will pass through a standard 49–1/2 inch rotary table. When running this system, the marine riser joints are run using conventional riser running techniques. After the riser joints are run, the rotation bearing joint is run and landed in the spider.