Reservoir Simulation of the Empire Abo Field: The Use of Pseudos in a Multilayered System
Authors: Killough J.E. , Foster H.P. 
Published: December 2007

Abstract
A three-layered model with vertical equlibrium pseudo-relative permeabilities and pseudo-capillary pseudo-relative permeabilities and pseudo-capillary pressures was used to match the results from a pressures was used to match the results from a 22-layered model of a portion of the Empire Abo field. Results of the two models were almost identical in both history match and prediction phases. Directionally dependent pseudo-relative permeabilities were introduced to match the drainage mechanism of the reservoir. Both horizontal displacement and drainage mechanisms can be modeled simultaneously in a multilayered system using these pseudo functions.The excellent comparison between the finely gridded model and the pseudo model allowed the simulation of alternative recovery schemes using the pseudo model with the same confidence as the pseudo model with the same confidence as the original three-dimensional model. In particular, a comparison between pressure maintenance with carbon dioxide and nitrogen was simulated, with a substantial savings in both manpower and computer time. Development of this pseudo model makes the simulation of the entire Empire Abo field feasible.

Introduction
For several years vertical equilibrium pseudo-relative permeabilities and pseudo-capillary pressures have permeabilities and pseudo-capillary pressures have been used throughout the industry to collapse a three-dimensional model with many layers to a two-dimensional areal model with a single layer. The obvious advantages of pseudo models are reduced computer and manpower costs. The justification for the use of pseudo models has been the comparison of results from one-dimensional models using pseudos with those from two-dimensional, cross-sectional models. Few comparisons have been made between an areal model using pseudos and a three-dimensional simulation.The Empire Abo field offered an excellent example for such a comparison. The field had been simulated in three dimensions, using 22 layers. An analysis of the simulation results showed that conditions were such that vertical equilibrium existed in most columns of the model. By applying pseudos to the three-dimensional model, it appeared possible to reduce the number of layers and associated computer time substantially.In this paper, the techniques for obtaining a match of the three-dimensional models with a pseudo model are described. The original three-dimensional model is described along with a history of the Empire Abo field. Coning correlations and directionally dependent pseudo-relative permeabilities also are described. Results between the pseudo model and the three-dimensional model also are compared. Finally, the use of the pseudo model for predicting alternative recovery schemes is discussed.

Field History
The Empire Abo field is located in southeastern New Mexico, about 8 miles (13 km) southeast of Artesia, NM (Fig. 1). The Abo reservoir was discovered by Amoco Production Co. in Nov. 1957. Subsequent development and unitization of the Abo reservoir was documented by Christianson. The producing horizon is a carbonate reef, basal Permian (lower Leonard) in age. The productive reef is about 12 1/2 miles (20.12 km) long and 1 1/2 miles (2.47 km) wide (Fig. 2), covering about 11,339 surface acres (45.9 x 10(6) m2). The reef dips gently from southwest to northeast at about 1 degree.
JPT
p. 279