Abstract

An original completion riser system, the so-called Drill Pipe Riser (DPR) has been developed which sharply decreases both subsea tree and tubing hanger running time. In addition, the cost of the system, including maintenance costs, is very low compared with conventional completion riser systems. The system is composed, basically, of drill pipes, control pod, surface control system, and control umbilical, which provides both annulus access and pod electro-hydraulic multiplexed control. An existing type of gas tight drill pipe has been adopted in order to minimize costs while improving reliability. Riser and connection analysis and tests have been conducted to verify DPR performance in water depths up to 2000m (6562'). This system has been designed to overcome problems associated with conventional completion risers which are very expensive, time consuming and require much space on rig deck. These problems increase with water depth and beyond 1000 m are very difficult to cope with. In other words, the deeper the water depth, the better becomes the DPR, compared with conventional risers. The paper describes the operational experience with the DPR from subsea completions in Roncador field, which have been performed at water depths ranging from 1500 to 1877m (6158'), the new world record. The paper also describes the development of a 2500 m (8202') Drill Pipe Riser, based on the operational experience of the 2000m one.

Introduction

Roncador, a giant field in the northern area of Campos Basin, was dicovered in October 1996 at water depths that range from 1500 to 2000 m. In January, 1998 another wildcat, RJS- 513, confirmed the extension of the reservoir and the existence of oil in the sothwestern portion of the reservoir. The exploitation of Roncador field is planned to be developed in three phases. The first one is underway in parallel with the appraisal phase in order to accelerate the production start-up of the permanent system. Phase 1 shall exploit the northern and the southeastern portions of the field and comprises 21 subsea production and 5 injection wells. The wells will be connected to the production unit by flexible/rigid flowlines and flexible risers. Phases 2 and 3 developments depend on more information from the reservoir and the conceptual studies will begin in early 2001. Petrobras decision to develop Roncador field just after the discovery was based on the success of its exploratory drilling, the improvement of 3D seismic technology and the result of the Technological Capability Program to produce oil and gas in ultra deepwater fields. Specifically, one of the major technological bottle necks associated with ultradeepwater subsea completions is the completion riser. The development of a completion riser for 2000 m was part of the forementioned program which had to be accelerated in order to meet Roncador field development schedule. Two systems were then developed. The first one, the Early Production Riser, which was installed by the SEILLEAN a Dynamically positioned FPSO which was connected to a single well, equipped with a special Subsea tree, through the EPR. This system has been successfully operating since January 1999.

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