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This paper Summarizes an interdisciplinary study performed to plan final Reservoir Development and Secondary Recovery Strategies for The Carito Field discovered in late 1987. Carito is a very large oil Field located in Northeastern Venezuela, with an estimated Volumetric Oil in Place of 1.8 Billion Stb. Production is mainly from Naricual Formation with a thickness of about 1300 feet in a faulted anticline. At the time of this Study, 25 wells had been drilled below 12200 ft ss. These wells were producing about 90000 Stb/D through 39 completions. Original reservoir pressure was abnormally high (11300 psig at 14040 ft SS) and the Temperature averages 300 degrees Fahrenheit. The field shows a graded fluid system that varies from a gas condensate to a medium oil. Gas cap to oil zone ratio is about 1.2 and crude oil gravity varies with depth from 36 to 21 API degrees. The simulation study, conducted to establish the optimum exploitation strategy, incorporated a detailed geologic model based on seismic, sedimentary environment, and production geologic concepts. The data from the geologic model, routine and special test data from conventional cores, and the data from 58 fluid analysis were consolidated in a numerical reservoir simulator model, which predicted the potential reservoir performance under various Development, Production and Secondary Recovery Planning. The results of this study led us to design a Gas Injection Secondary Recovery Process encompassing a rate injection of 600 MMScf/D through 10 injector wells and the perforation of an additional 16 producer wells. We expect to double the natural depletion oil Recovery as a consequence of the Pressure Maintenance Program. Introduction The Carito Field was discovered in September of 1987 and is located in the State of Monagas, 40 Kms. to the west of its capital Maturin and 500 kIns. to the east of Caracas (fig. 1). The discovery well (MUC-1E) which penetrated Oligocene Naricual formation and reached Cretaceous formation at a depth of 15000 feet, showed an initial production rate of 4000 Stb/D through a completion from the upper part of the Naricual formation. The field has been producing an average of 90000 Stb/D of oil, with a GOR of 1400 Scf/Stb. As of March 1995 the field has accumulated 200 MMStb of oil (11% of IOIP) through 39 completions. This study was performed using a 3D-three phase Black Oil Simulator with the "Volatile Oil" option to represent de gas condensate behavior. P. 587

Corpoven, S. A. an operating Affiliate of Petroleos de Venezuela, S. A. has recently Petroleos de Venezuela, S. A. has recently commenced production from a newly developed oil province located in the northern sector of the province located in the northern sector of the state of Monagas, eastern Venezuela. Simulation of well stream phase behavior and production fluid pressure vs. temperature production fluid pressure vs. temperature traverses in the CARITO 1-X well have indicated that some horizons defined as gas condensates produce fluids to the surface via the normal produce fluids to the surface via the normal condensation process, while other sands also defined as condensates produce to the surface as a light oil or quasi-critical hydrocarbon liquid. Numerical evaluations have shown that the latter case occur at certain fluid transport rates via a progressive transition of the gas from the dense phase to the single phase liquid region. This flow responds to the flowing pressure vs. temperature relationship in the pressure vs. temperature relationship in the wellbore above the critical pressure and temperature of the fluid. The identification and description of this anomalous behavior is very important to Corpoven's North Monagas operations because it allows for proper identification of CONDENSATE GAS RESERVOIR production. This classification receives special OPEC consideration under existing technical definitions. This paper deals with the reservoir fluid characterization procedures, simulation techniques, and phase procedures, simulation techniques, and phase equilibrium considerations required to properly identify the producing horizons in the CARITO-1X well. Introduction The CARITO 1X well belonging to the "New Areas of Northern Monagas, field was drilled during September 1987. The final objective of this well was the Caratas Formation, a Cretaceous accumulation at 13000 ft (3963 m). The well reached a TD of 15000 ft (4573 m) and was successfully completed in November 1987. The following stratigraphic column was clearly identified in the well:CARAPITANARICUAL SUPERIORNARICUAL INFERIORLOS JABILLOS The sands pertain to the Oligocene, Eocene, and Cretaceous sands of the CARITO field, and border the CARITO WEST field to the West, along with the FURRIAL-MUSIPAN field to the East. The well produced some 4805 BOPD (7654 M3/D) of 31.1 degrees produced some 4805 BOPD (7654 M3/D) of 31.1 degrees API condensate at a total GLR of 3891 SCF/STB (691 SCM/M3). The fluid from the well corresponds to the NARICUAL SUPERIOR Sand. Five (5) horizons were sampled in the well in order to identify and characterize the original fluids in the laboratory. Chromatographic analysis of the hydrocarbon content through Eicosanes + (C1-C20+), and NSO) compounds yielded a strong paraffinic fluid with a Watson Factor (Kw), of approximately 12.5 Initial reservoir conditions are given by Table 1. Each one of these intervals was represented by a proper PVT study in accordance with the proper PVT study in accordance with the condensate or quasi-critical nature of the reservoir fluid. For the first four (4) condensate sands shown in Table 1 the reservoir study was comprised of four basic procedures as follows:Fluid Analysis: Liquid/gas recombinationRelative volume vs. pressure at reservoir temperature determination. P. 301