Abstract

This paper describes the successful experience obtained in using electro-submersible pumps (ESP) in the production of abrasive and corrosive fluids. The study covers 60 wells operated by the Consorcio equiped with ESP's in Oritupano-Leona field, States of Anzoategui and Monagas, East Venezuela.

The influence of the reservoir on the pump run life is reviewed. Currently, 46% of the total oil is produced through ESP's, the first instaled in 1996. Most of the failures are related to sand production and corrosion. Since the start of this program, pulling jobs due to ESP's failures have been significantly reduced, due to practices that increase the run life of the pumps, including:

  1. a start-up procedure to reduce fines production

  2. an exhaustive, teamwork based, study of the failures

  3. the use of special abrasion / corrosion resistant materials

All of these factors combined have allowed to optimize the application of ESP's in this field. Details of the various methodologies used to achieve the optimization of the ESP system in Oritupano and Leona fields are presented.

Introduction

The Oritupano-Leona block is located in East Venezuela and covers part of the Anzoategui and Monagas States (Figure 1). Within the block, Oritupano and Leona fields are located. The block was assigned by PDVSA (Venezuela State Oil Company) to the Consorcio Perez Companc-UPR-Corod in 1994.

In the two fields there are about 60 wells equipped with ESP's. The first pump was installed in November 1996. During 1997 there were just a few installations with different results. At the beginning of 1998 the Consorcio decided to start with ESP's as a special project to develop different areas of the field with high IPR's. (Figure 2 and 3). In March 1998, the Consorcio began an Alliance with a pump supplier company.

In Oritupano and Leona fields there are areas with medium-heavy crude in the upper Oficina Formation, and an extra heavy crude at its bottom section. There are vertical, directional and horizontal wells producing with ESP's, some of them gravel packed.

ESP's application began with standard equipment of different rates. Due to the aggressiveness and corrosiveness of the fluid produced, material specifications have been changed. Now the pumps are producing volumes up to 10.000 bfpd using variable speed drivers (VSD) and plans have been made to increase the flow rates in some areas of the field.

The Initial Problems

After the first installations several problems arise:

  1. High Sand Production

  2. Corrosion

  3. Scale

Various wells have sanded up after only a few days of being in service, even though the startup rate was low. The sanding up became critical initially because in one month there were 5 interventions due to pump seizing. At that time, the application of this production system in some zones of the field was in doubt. The pumps lasted from 5 to 20 days until they seized up.

Corrosion due to CO2 was found to be present in various wells where we noted large holes in the housing of the motors and seals in many cases combined with erosion due to sand production. In one of the wells, the corrosion failure was produced after 98 days of being in service.

Most of the fluids produced in Oritupano-Leona have a scaling tendency but just a small group of wells showed evidence of calcium carbonate after being pulled out. Seizing up due scale took place in one of the wells after being in production 60 days.

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