ABSTRACT
The effects of gas injection into two gas condensate reservoirs in eastern Venezuela were analyzed in order to establish optimum exploitation schemes. One of the reservoirs, the M3U sand, MVR-52, in the Zapatos field, is actually subjected to a pressure maintenance process. The other reservoir, the S3M sand, SG-44, in the Mapiri field, is a dual gas condensate, black oil reservoir, currently at a primary depletion stage.
Sensibility studies were made for both accelerated natural depletion and pressure maintenance through the injection of lean gas. These simulation studies were made utilizing a phase behavior simulator and a compositional simulator (COMPSIM). The first was used to calculate equilibrium constants at different pressure. In order to achieve this, it was necessary to characterize the fluids in function of six (6) pseudocomponents, which represent the mixture of the pure components as given by PVT analysis.
COMPSIM is a three-dimensional, three-phase, compositional simulator, which allows to compute pressure and saturation distributions, as well as the distribution of the fluid components in the oil gas-condensate phases. Mass exchange of each component between oil and gas phases is ruled by the equilibrium constants under conditions of thermodynamic equilibrium.
In the case of the M3U/MVR-52, after introducing pseudocomponents for the characterization of initial fluid compositions, the dew point pressure, liquids deposition and relative volumes were matched using the compositional phase simulator. Production and pressure history matching were attained through the COMPSIM.
The S3M sand, SG-44 reservoir also belongs to the lower section of the Oficina formation of lower Miocene age. The depositional environment consists of a north to south oriented deltaic channel at the center of the reservoirs, and splays with poor sand development toward the borders.
The S3M is a well defined, homogeneous sand body, thinning out to the east and to the west. Due to its depositional environment the sand shows little variations in thicknesses.
The reservoir is bounded to the north by a water-oil contact, to the east and west by changes of facies and to the south by a fault, Fig. 3.
