Non-Integral Production Riser For Green Canyon Block 29 Development

Abstract

ABSTRACT The first floating production system has been installed in the Gulf of Mexico utilizing a unique, rigid, non-integral, self-supporting production riser with a titanium flex joint - at the base. The system allows simultaneous development drilling and well production to a modified semi-submersible moored in 1534 feet of Water. The riser, locked to a subsea template, provides individual access and surface control to each well and can remain connected during the life of the field including 100-year storm conditions. The riser terminates about 150 feet under the ocean surface and has flexible lines that act as jumpers to connect the riser to the vessel. The rigid riser is installed with conventional drilling-riser installation procedures using standard tubulars for production, annulus, oil and gas sales lines. All but the gas sales line down the center of the riser are free to move in guide tubes thus minimizing stresses from riser bending and from temperature/pressure changes. The riser provides only structural support for the tubulars, and during installation riser joints do not require pressure testing. Pressure-containing lines are run one at a time after the riser is in place, and each line can be indvidually pressure tested when installed. The system provides a cost-effective alternative for marginal fields in deepwater, while also allowing a shorter lead time to first production. SYSTEM DETAILS The Green Canyon Block 29 floating production system, located south of New Orleans in 1534 feet of water, is the first floating production system installed in the Gulf of Mexico. The system consists of a subsea template for 24 wells with connections for satellite trees and sales lines, a converted semisubmersible for production and drilling, and a selfsupporting production riser. The template is a space frame structure with integral plumbing for well production, annulus access, sales lines, tree control and satellite well connections. Twenty of 24 slots are used for template trees; the other four serve satellite wells. Connections for sales lines to a shallow-water platform are at one end of the template with an integral riser base at the other. The riser base consists of a hub profile centered between four radially located posts and four pile sleeves. Forty-nine vertical female receptacles surround the hub to provide production/annulus/oil-sales line connections to the riser. Within the central hub connection, at a slightly lower elevation than the others, is a vertical receptacle for the gas-sales line. Production and annulus lines are 2-7/8", 7500 psi. The oil-sales line is an 8", 2160 psi line and the gas-sales line a 12", 2160 psi line. The subsea trees, both satellite and template, are 3 × 1-13/16 wet, non-TFL completions with ROV override on the gate valves. Trees are controlled from the surface via two hydraulic control bundles, 7" in diameter, which are run through guides along the side of the riser after riser installation.