The Gladys McCall geopressured reservoir consists of an interbedded sequence of relatively thick sands and thin shales. The lateral extent of the reservoir is not well defined. Gladys McCall Well No. 1 produced approximately 4.0×106 m3 (25×106 barrels) of brine from Sand Zone No. 8 from October 7, 1983 through May 1987. Analysis of the flow data from the well has led to the development of a conceptual model of the reservoir, which depends on cross-flow from sands overlying/underlying Sand Zone No. 8 for the observed pressure maintenance. The fluid source is remote from the well in the sense that the fluid from the neighboring sands must flow a long distance to find a vertical pathway around the intervening shale stringers in order to recharge Sand Zone No. 8. A reservoir simulation model based on the conceptual model provides an excellent match to the detailed downhole pressure buildup measurements made during the original Reservoir Limits Test and two subsequent short-term buildup tests. The model has also been employed to match the production history of the Gladys McCall No. 1 well and to predict future reservoir response. Nevertheless, the reservoir model employed is not unique and alternate models for pressure maintenance are also being investigated.

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An equation-of-state package for water-carbon dioxide mixtures has been constructed from available thermodynamic data that covers the range interest to the Baca reservoir system. The package has been to examine the thermodynamic state of the Baca reservoir fluid for conditions o f temperature, pressure and C02 content believed to bracket conditions existing at the production depth of the wells in the Redondo Creek area. It is shown that the reservoir fluid may be either all-1 iquid or two-phase at various well locations and depths, depending on the C02 content. It i s also shown that the C02 content at reservoir conditions cannot be re1 iably inferred from pressureltemperature measurements made on flowing wells. The eq on-of -state package has been incorporated into a general purpose thermal reservoir simulator and a series of calculations made which show that the C02 content of the produced fluid be less than or greater than that of the reservoir fluid, The char of the produced fluid are sensitive to the GO2 content TABLE OF CONTENTS SECTION 1 INTROOUCTION 1.1 . Introduction 1.2 Scope of the Report 1.3 Summary and Conclusions 1.4 Recommendations for Future Study SECTION 2 EQ U AT I ON-OF4 TATE PACKAGE 2.1 Introduction 2.2 Summary 2.3 Calculational Procedure 2.4 Partition of Carbon Oioxide 2.5 Specific Volume and Energy of Mixture Components 2.6 Viscosity of Mixture Components 2.7 Thermal Conductivity of Mixture Components 2.8 Energy of Solution SECTION 3 EFFECTS OF C02 ON BACA RESERVOIR STATES P a g e 3.1 Introduction 3.2 Summary 3.3 Effects of CO2 on Thermodynamic States 30 3.5 EFFECTS OF C02 ON WELL FLOWING TESTS 3.4 Effects o f CO on Baca Reservoir Conditions Need for Chem ? cal Measurements of Baca Discharge F1 ui ds SECTION 4