Abstract

This paper presents the results of the optimization process carried out in wells JOM-38, JN-3, CD-l and CC-7 located in the Jobo and Cerro Negro Fields, using horizontal drilling techniques and electrical submersible pumping as a lifting system.

These wells originally had been drilled vertically, in an unconsolidated formation of reservoirs with strong water drive, obtaining initial oil production rates in the order of 250 STB/D of 8.5 API and 2500 cP at reservoir conditions. However, because of the adverse mobility ratio, the oil production dropped drastically with time and water production increased substantially (less than 50 STB/D and 85% water-cut) making these wells uneconomical.

Due to the low performance, the wells were re-entered with an average horizontal sections of 1550', obtaining production rates in the range of 350 - 500 BOPD/well using progressing cavity pumps as means of artificial lift. These rates were still below the expected 1000 BOPD predicted.

In view of these results and considering the high productivity index measured in these reentry wells, a pilot project was developed, changing the existing lifting system for an electrically driven submersible pump. The new production rates thus obtained varied from 700 to 1300 BOPD/well, with a watercut in the order of 10 percent.

Introduction

Venezuela possesses one of the largest heavy crude oil and bitumen (8.5 - 9.0 API) accumulation in the world; located in the Orinoco Belt region and Jobo field.

Heavy and extra-heavy oils have been traditionally produced by means of vertical wells with sucker rods as the lifting system, achieving a cold production of up to 250 STB/D.

In the last years, new technologies have been applied in the oil industry to optimize oil production. A combination of horizontal well and lifting methods such as sucker rods, screw pumps and electrosubmersible pumping have been evaluated to determine an efficient and economic way to exploit the huge heavy oil reserves.

Among the lifting methods, electrosubmersible pumping seems to be an attractive system to produce heavy oil wells with high productivity index (able to produce more than 1000 STB/D).

Four horizontal re-entries with high productivity index (two in Jobo field and two in Cerro Negro field) were selected for electrical submersible pump installation, obtaining substantial increase in production.

The pilot test was carried out injecting diluent (diesel refinery cut) at different rates and monitoring the dynamic fluid levels while the pump frequency was increased from 40 to 60 Hz. In this paper, the results of the tests are presented.

Geographic Location.

Wells JOM-38, JN-3, CD-1 and CC-7 are located in the Jobo and Cerro Negro fields in the Eastern part of Venezuela just North of the Orinoco river at Monagas State (Figure 1).

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