Reservoir Design Factors For A Single Pattern, Tertiary Pilot
Authors: Harmon Richard A. 
Published: December 2007

Taking a promising laboratory process to the field is a critical step in the evaluation of a tertiary oil-recovery process. How the field test is conducted has as much influence on pilot oil production as how the process really performs under production as how the process really performs under field conditions. A poorly executed test can conceal the true performance of an otherwise effective process. Conversely, barrels of oil in the tank can process. Conversely, barrels of oil in the tank can be misinterpreted as indicating that a process is more successful than it actually is.

This paper presents an approach to tertiary test operation designed to improve the interpretability of a single-pattern pilot test. Five key reservoir engineering factors are covered. These factors reflect the need for detailed engineering design in order to obtain a meaningful evaluation of the tertiary process under field conditions.

Introduction

A potential tertiary oil-recovery process is labeled a "successful laboratory process" only after it has been thoroughly tested and quantified. In the laboratory, it can be shown that each process slug size (a known percent of the pore volume of the test core) can displace a measured fraction of the waterflood residual oil volume. The question then remains: How well will the process perform under field conditions?

Primary and secondary goals for meaningful field test pilots can be defined. The primary goal is to make the pilot test quantitative so that it will be a fair test of the tertiary process being investigated. A secondary goal is to complete the process evaluation in a realistic time frame so that process evaluation in a realistic time frame so that costs can be minimized and use of the test results can be made as soon as possible. The primary goal is to insure the success of the pilot field test as an effective evaluation tool. Whether the recovery process turns out to be good, fair, or poor, we want process turns out to be good, fair, or poor, we want to have confidence in the evaluation of the field test. Then there will be a sound basis for subsequent decisions regarding the process.

Ideally, field evaluation would be analogous to laboratory core runs. Cumulative tertiary oil production would be determined from the total oil production would be determined from the total oil production and related back to a reservoir pore production and related back to a reservoir pore volume and a waterflood residual oil saturation. Also, the process slug size (percent pore volume) would be determined from the volume injected and the same reservoir pore volume. However, determining these quantities in the field is much more difficult than in the laboratory.

Therefore, another goal of the engineering design is to minimize uncertainty in the field data and improve the quality of the information obtained from the test.

With these definite goals in mind, an approach to designing tertiary pilot tests is outlined and discussed in the following five sections. The discussion of this design approach will be limited to a single, isolated well pattern. Other types of pilot tests may require a different approach. Recall pilot tests may require a different approach. Recall that considerable work already has been reported on the design of secondary field pilot tests as referenced in a series of articles by Smith. Also multiple-pattern field tests may not be amenable to all of the following suggestions.

The single-pattern pilot offers considerable opportunity to control pilot operation and enhance the quality of the resulting field data. This paper is directed toward those areas.

PATTERN CONFINEMENT PATTERN CONFINEMENT If the well pattern of the pilot test is the same in all respects, except size, as that intended for the field-wide application, scale-up of pilot performance to commercial well spacing will be more performance to commercial well spacing will be more straightforward. The pilot pattern also will point out potential problems with the choice of well arrangement. The commercial development usually will incorporate a repeated well pattern.