Abstract

A methodology for evaluating a complex reservoir for an EOR process is presented in this paper. In this methodology, two factors are emphasized. First, utilization of a stagewise workplan with numerous go/no-go decision points is shown to be important in avoiding the expenditure of significant time and money in the application of an EOR process to an inappropriate reservoir. Second, the importance of a multi-disciplinary workteam is emphasized. The tasks required to carry out such a reservoir evaluation involve diverse knowledge and skills beyond the ability of any one discipline. Finally, the workplan must be tailored to the specific needs, or characteristics, of the reservoir.

In this paper, we evaluate the South Cuyama Field for the application of Micellar-Polymer Flooding. The South Cuyama reservoir is a mature field in California that has both complex geology and a complex operational history. Two factors were found to be critical in determining the viability of the micellar process in South Cuyama. First, the faulted nature of the South Cuyama sands emphasized the importance of sand continuity between injectors and producers. Second, in order to make the EOR process profitable, the remaining oil in South Cuyama had to be large enough to justify the added expense of process implementation.

This paper presents the results of a multi-disciplinary study by engineers, geologists and geophysicists from the Research, Engineering, and Operations organizations. This study starts with preliminary reservoir screening based on average reservoir properties, progresses through the reanalysis of existing properties, progresses through the reanalysis of existing data to acquire an updated picture of the reservoir and determine the key questions to be answered, describes a joint geological/geophysical study which included a 3D, high-resolution seismic study, reports the results of field work done in existing wells, presents the results of updated material balance and volumetric studies, and describes the drilling and coring of a reservoir delineation well along with the analysis of the core. Particular emphasis is placed on determining the Particular emphasis is placed on determining the amount and distribution of remaining oil saturation, which is studied by log-inject-log tests, single-well tracer tests, laboratory core analysis, reservoir performance, and OOIP studies. The progression of the workplan is in the order of increasing effort and expense. As key questions are identified and critical data found lacking, we progressed logically to the next step. The results of this study show that South Cuyama is not a good candidate for micellar-polymer flooding. Using the methodology presented here, we were able to determine this fact without actually running a pilot test, thereby saving considerable expense.

Introduction

The incentive for applying Enhanced Oil Recovery (EOR) technology increases as mature fields reach the end of their productive lives. In considering the application of EOR to any reservoir, uncertainties exist which ultimately determine the economic viability of a project. These uncertainties fall loosely into two, highly project. These uncertainties fall loosely into two, highly interrelated categories; those associated with the process and those associated with the reservoir. The process and those associated with the reservoir. The objective of the work presented in this paper is limited to determining as much a possible about the reservoir prior to the implementation of a process pilot. The amount of information needed to implement EOR is greater than for conventional primary and secondary operations.

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