Offshore Heavy Oil in Campos Basin: The Petrobras Experience
Authors: Capeleiro Pinto A.C. , Branco C.C.M. , de Matos J.S. , Vieira P.M. , Guedes S. da Silva , Pedroso C. , Coelho A.C. Decnop , Ceciliano M.M. 
Published: October 2008

Significant volumes of heavy and high viscosity oil have been discovered in the Campos and Santos Basins, offshore Brazil, and its economical production is a challenge for the oil industry.

New production technologies are required for the economic development of offshore heavy oil reservoirs. Long horizontal or multilateral wells, produced with high power ESPs, hydraulic pumps or submarine multiphase pumps, could partially compensate the decrease in productivity caused by the high oil viscosity. The flow assurance could be improved with insulated or heated flowlines or, alternatively, with the use of water as the continuous phase. The heavy oil processing in a Floating Production Unit is not straightforward, and new separation technologies, as well as the feasibility of the heavy oil transportation with emulsified water, should be investigated. The existence of light oil reserves in neighboring reservoirs, even in small volumes, would be an important issue for the commercial feasibility of the heavy oil area.

The Petrobras experience with offshore heavy oil fields in the Campos Basin shows that some can be economically produced. However, the economic feasibility is controlled by factors such as: reservoir characteristics; water depth; possibility of blend with light oil; oil acidity and contaminants; price scenario; fiscal regime; availability of new production technologies; transportation, refining and marketability of the heavy oil.

The recently created Petrobras Heavy Oil Technological Program " PROPES " is in charge of the development, together with universities, service companies and the industry, of new technologies for the offshore heavy oil fields. The main objective of all this work is to set the basis for the economical development of the significant volumes of heavy oil already discovered offshore Brazil.

This paper presents the main research and development topics of the Petrobras Heavy Oil Program, as well as the key production technologies for the target fields. Additionally, the results of some well tests and Extended Well Tests (EWT) in heavy oil reservoirs in the Campos Basin are presented and discussed.

Introduction

In the Campos and Santos Basins, heavy oil is being generically defined as any oil that is heavier or more viscous than the Marlim Field oil. The Marlim Field (ref. 1), located in the Campos Basin under water depths from 650 m to 1,100 m, in operation since 1991, currently produces around 98,000 m3/d (620,000 bpd) of a 19°to 22° API crude. The Marlim live oil viscosity is between 4 and 8 cP and the dead oil viscosity is between 400 and 500 cP at 20° C.

The industry reference for offshore heavy oil production isthe Captain Field, located in shallow water in the North Sea, operated by ChevronTexaco (refs. 2-5). The Captain oil viscosity at reservoir conditions is about 90 cP (refs. 2-5), much higher than the Marlim oil viscosity. However, at surface conditions, the viscosities of both oils are quite similar. As some of the offshore heavy oils recently found offshore Brazil are more viscous than the Marlim and Captain crudes, at surface conditions, the production process will be much more challenging.