Characterization of gas condensate reservoirs using pressure transient and production data - Santa Barbara Field, Monagas, Venezuela

Abstract

This thesis presents a field case history of the integrated analysis and interpretation developed using all of the available petrophysical, production, and well test data from the condensate zone of Block A, Santa Barbara Field (Monagas, Venezuela). The reservoir units in Santa Barbara Field present substantial structural and fluid complexity, which, in turn, presents broad challenges for assessment and optimization of well performance behavior. Approximately 60 well tests have been performed in the gas condensate sections within Santa Barbara Field, and the analysis and interpretation of this data suggests the existence of condensate banking and layered reservoir behavior, as well as "well interference" effects. We demonstrate and discuss analysis and interpretation techniques that can be utilized for wells that exhibit condensate banking, layered reservoir behavior, and well interference effects (where all of these phenomena are observed in the well performance data taken from Block A in Santa Barbara Field). We have established that the layered reservoir model (no crossflow), coupled with the model for a two-zone radial composite reservoir, is an appropriate reservoir model for the analysis and interpretation of well performance data (i.e., well test and production data) taken from wells in Santa Barbara Field. It is of particular importance to note our success in using the "well interference" approach to analyze and interpret well test data taken from several wells in Santa Barbara Field. While it is premature to make broad conclusions, it can be noted that well interference effects (interference between production wells) could be (and probably is) a major influence on the production performance of Santa Barbara Field. In addition, our well test analysis approach corroborates the use of the Correa and Ramey (variable rate) plotting function for the analysis of drillstem test (DST) data. In summary, we are able to use our integrated analysis developed for Block A (Santa Barbara Field) estimate areal distributions of "flow" properties (porosity, effective permeability, and skin factor), as well as "volumetric" properties (original gas-in-place, gas reserves, and reservoir drainage area (all on a "per-well" basis)).