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Abstract: Methodology Applied in a Successful Water-injection Pilot Program in The Cretáceo-01 Reservoir, El Furrial Field, Venezuela

Mengual, Raul; Jose Sanchez; Nidia Pinto and Marino Giusto - PDVSA

The Cretáceo-01 reservoir is located 13 miles east from Maturin City, Venezuela. It is one of the two reservoirs existing in the El Furrial field, and was discovered in 1987 by the FUL-4 well, with an initial production of 4000 MBD of 27° API.

The reservoir is an anticlinal, 700 ft thick, 14500 ft deep, cretaceous formation filled with overpressured, asphaltenic oil. The original pressure of this reservoir was 11250 psi, with a bubble point of 2850 lpc. Average reservoir temperature is approximately 300° F. Permeability and porosity are 40 md and 11% respectively. The production mechanism is fluid and rock expansion. An aquifer exists underlying the reservoir, but a tarmat zone prohibits any pressure effect on it.

During the exploitation process of the reservoir, a compartmentalized system was detected, and three zones with different -and high- pressure declination were identified. Integrated studies showed that water injection was necessary in order to re-pressurize the reservoir from 6500 psi to 7000 psi, avoid asphaltene precipitation and increase reserves up to 190 MMBls.

This paper shows the methodology used in the pilot well design, using PLT's information, core data, petrophysic data and production performance of the 14 wells completed. The results obtained with this methodology were excellent. The pilot well has an homogeneous injection profile, the injection rate is 50% above the initial estimates, and the operating pressure design for the injection plant was adjusted 500 psi down, with a significant cost reduction.

AAPG Search and Discovery Article #90933©1998 ABGP/AAPG International Conference and Exhibition, Rio de Janeiro, Brazil