Abstract: Reservoir Characterization, Modeling, and Simulation in the Welch San Andres Field

Rene Ulmschneider

As a part of a DOE funded Class II project aimed at improving oil recovery in shallow shelf carbonate reservoirs, detailed characterization, modeling and reservoir simulation is ongoing in Oxy USA's West Welch Unit in the Welch, San Andres field. The initial effort at modeling the reservoir, which is described in this report, is based on all the available core and log data in the study area. A final report will compare these results to reservoir modeling enhanced by high resolution seismic data obtained from cross wellbore tomography.

The reservoir model was built using the following methodology:

(1) Determine sequence stratigraphic framework from core data.

(2) Identify rock fabrics from thin sections.

(3) Quantify porosity versus permeability relationship for each rock fabric.

(4) Identify rock fabrics from log data.

(5) Use unique porosity versus permeability relationship for each rock fabric to transform log porosity to permeability.

(6) Define reservoir model flow units using sequence stratigraphic framework and identified rock fabrics.

Each layer (flow unit) is then mapped, gridded and exported to the simulator. The simulation can then be compared to actual production history. Using this methodology a good history match was easily obtained from the simulation with very little modification of the simulation parameters in two different Welch field model areas. These results give great confidence in the subsequent simulation of reservoir response to CO₂ flooding.

AAPG Search and Discovery Article #90960©1995 AAPG Southwest Section Meeting, Dallas, Texas