Abstract

The Peregrino field is located in Campos Basin approximately 85 km offshore from Cabo Frio in Brazil. The oil in Peregrino is heavy with a gravity of 14° API. First phase of field development will be accomplished by two drilling capable wellhead platforms tied back to a central FPSO. A Total of 30 producer and 7 water injector wells are planned for this phase.

One of the most critical factors in offshore operations is physical space. Flow allocation devices like test separators can be bulky due to the large capacities required to operate with heavy oil. These and the gear required for their control and efficient operation like heaters can be among the most space consuming equipment onboard. Multiphase flow meters are also available for flow allocation purposes; however its accuracy is highly impacted by heavy oils. The slow gas flashing out of heavy oils affects the representativeness of necessary pressure-volume-temperature (PVT) characterization.

Downhole Venturi meters were other alternative considered when deciding about the flow allocation method for Peregrino. These were initially left behind basically due to two factors; the economical impact related with a single unit required per well and the limited data available regarding its uncertainty with viscous oil. The changing oil/water conditions in Peregrino can be a challenge from a viscosity modeling point of view. Therefore a decision was made in favor of the flow allocation based in Electric Submersible Pumps (ESPs) performance. This technique has been used with success in wells with very high water cuts but it's a novel approach in viscous oil.

Improving the accuracy of this approach required multiple tests with the submersible pump models selected for Peregrino field. The tests were performed in a high viscosity flow loop in Claremore and covered a wide range of viscosities and speeds. This paper outlines the test results and presents the principles of flow allocation in Peregrino.

Introduction

Statoil is currently developing the Peregrino field in offshore Brazil (see Figure 1). The Peregrino project is the company's largest internationally operated field and biggest project outside of Norway to date. This is a large scale project with an estimated 2.5 billion barrels of oil. First Oil production started in March 2011. The field is located in Campos Basin approximately 85 km offshore from Cabo Frio in Brazil at 100 m water depth. It consists of two wellhead platforms tied back to a central FPSO (see Figure 2). Thirty horizontal oil producing wells are planned to be drilled from the platforms during the first development phase.

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