Petrozuata - An Application of Multiphase-Metering Technology
Authors: Denney Dennis 
Published: February 2015

This article, written by Technology Editor Dennis Denney, contains highlights of paper SPE 89870, "Petrozuata - An Application of Multiphase-Metering Technology," by Luigi Bortolin, Petrozuata C.A.; Parviz Mehdizadeh, SPE, Production Technology Inc; and Gordon Stobie, SPE, ConocoPhillips, prepared for the 2004 SPE Annual Technical Conference and Exhibition, Houston, 26-29 September.

Previous applications of multiphase meters (MPMs) usually deployed only a few meters. Petrozuata, in Venezuela, installed an operation with 37 MPMs, and the system has been in use for more than 5 years. This paper describes the facility and the operations of the MPMs. The full-length paper details the difficulties experienced and the operational results from the extensive use of such measurement techniques.

Introduction

Petrozuata is a joint-venture strategic association owned by ConocoPhillips (50.1%) and Petróleos de Venezuela S.A. (PDVSA), the national oil company of Venezuela (49.9%). The project is a fully integrated crude-oil production and processing business, in the state of Anzoátegui, Venezuela. Although commercial operations began 12 April 2001, first production of the extra-heavy crude oil (EHCO) was in mid-1998. Petrozuata’s primary function is to produce EHCO from the Zuata region of the Orinoco oil belt, transport it to the Jose industrial complex on the north coast of Venezuela, upgrade it into 19 to 26.5°API synthetic crude, and market it along with 14°API oil and associated byproducts (e.g., liquified petroleum gas, sulfur, and petroleum coke).

The strategic association has a 35-year operating life, during which more than 750 wells will be drilled. The estimated recovery is approximately 1.6 billion bbl of EHCO. This facility uses a proprietary coking technology to upgrade heavy crude oil into lighter synthetic crude at a capacity of 120,000 BOPD. Currently, Petrozuata produces more than 125,000 B/D of EHCO.

Since 1997, Petrozuata has drilled more than 260 wells (currently, 195 active producers) in a 56,000-acre area of the Zuata region. A further 490 wells will be drilled during the next 30 years to drain the reservoir. The wells are clustered around 37 production pads.

Production is moved around the field by eleven 2,000-hp multiphase pumps (MPPs), with the EHCO diluted with naphtha. Within the field, the production is metered and allocated by use of 37 MPMs, one at each production pad, as shown in Fig. 1. The diluted crude is processed (degassed and dewatered) at a central processing facility, after which it is fiscally metered and pumped to the upgrader through a 125-mile-long 36-in.-diameter pipeline.

Heavy- and Extraheavy-Oil Production

Two of the major problems recognized early in the development of the Petrozuata field were the process issues posed by the oil viscosity and by gas/oil foam and oil/water emulsion. The diluent-based production scheme is effective for reducing the viscosity. As Fig. 2 shows, because fluid viscosity is inverse additive, a relatively small volume of diluent greatly reduces the mixed-fluid viscosity. Also, the day and night ambient-temperature variations have a significant effect on the fluid viscosity.

The original reservoir pressure was below the bubblepoint. Therefore, the oil was foamy at reservoir conditions.