Roncador Field Development - The Impact of Fluid Properties
Authors: Minami Kazuioshi , Cardoso Carlos A.B.R. , Bezerra Maria C.M. , Melo Aglairton P. 
Published: October 2008

The impact of produced fluid properties on the strategy for developing the giant Roncador Field is described in the present work. Potential problems associated with wax, hydrates, scales and corrosion were identified as the most troublesome ones to be dealt with, during the conceptual design phase of this ultra-deep water, 4,920 to 6,560 ft (1,500 to 2,000 m), field development.

The current system layout resulted from adjusting to and compromising among several technological limits imposed by the following areas: mooring, pipeline laying, artificial lift and flow assurance.

The characteristics of the produced fluids have indicated that the engineering design had to carefully take into account the potential problems associated with them. In the initial design of Roncador Phase I development, their impact on the economics was considerable, but they were gradually worked out through modification in the design as the fluid property data were gathered.

Introduction

The giant Roncador Field was discovered in October 1996 through the wildcat well RJS-436 drilled in 6,079 ft (1,853 m) ultra-deep waters. It is located in the northern part of the Campos Basin, 77.7 mi. (125 km) off the Rio de Janeiro State Coast(1,2). The field covers 51 sq. mi. (132 km2) and water depths from 4,920 to 6,560 ft (1,500 to 2000 m). During the formation evaluation tests of its main upper cretaceous (Maastrichtian) reservoirs the well yielded the much needed light crude oil (31 API grade) as compared to other oils from this basin.

The size of the field and the quality of the crude found in Roncador have led the Company to start its development as fast as possible.

Designing a new system to produce from this record breaking depths presented challenges of its own, but others would have to be faced. To accelerate the production start-up, a new development strategy was adopted, in which the project was divided into three phases(3,4). Phase I was to be implemented in parallel with the appraisal phase, following the decision to use the P-36 FPU, a Floating Production Unit based on a semi-semisubmersible, and P-47 FSO, a Floating Storage and Offloading tanker, both under construction for another development project. As a result, a subsea production system was to be used.

This posed a challenge to the design team, as the FPU and FSO were designed for a different scenario: shallower water, lower flowrates and heavier crude. In addition, the reservoir and fluid property information of the newly discovered field was not sufficient to allow a sound engineering design. Therefore, the adaptation of the FPU and FSO, and the definition of the subsea arrangement had to be performed while information from appraisal and extension wells was still being gathered. Available data in early 1998 indicated that the reservoir structure in this field was far more complex than anticipated. The Southwestern portion of the field held a much heavier oil reservoir (18° API), while in the Northern part, the water-oil contact was found at different elevation from the contact seen in the RJS-436.