Production Well Tests -- Facts and Fiction
Authors: Engelman Charles 
Published: December 2007

American Institute of Mining, Metallurgical and Petroleum Engineers, Inc.

This paper discusses production well testing. It includes a study of the information needed, the methods and types of equipment used in obtaining this information, and the limitations and causes of error in the various methods. Simple graphs and formulas are included to aid engineers and field personnel in the interpretation and utilization of the test information.

Introduction

The economical operation of oil production necessitates constant improvement of operating techniques. Increasing costs of material and labor are narrowing the profit margin and forcing production engineers, field superintendents, foremen and management to operate together with precision or face a continual increase in lifting precision or face a continual increase in lifting costs. The entire production process must be coordinated from the original completion to abandonment. Decisions to stimulate wells, install larger equipment and to initiate pressure maintenance can be very costly if made incorrectly.

Most of the bad decisions are made not because of any lack of ability or intelligence in engineering or management, but because the person making the decision either did not have person making the decision either did not have enough individual well data to analyze the situation, or the data he used were incorrect.

Management must continually stress the need for accurate and complete individual well performance data, such as the amount of oil, performance data, such as the amount of oil, water and gas a well is capable of making with a certain bottom-hole pressure or fluid level. Pressure buildups, pressure drawdowns, and Pressure buildups, pressure drawdowns, and capacities are also necessary information. Well testers, fluid level instruments dynamometers, amp meters, bottom-hole pressure devices, tachometers, tape measures and stop watches should all be used to gather data for production analysis. production analysis. Since it is the opinion of the author that the production well tester is the most important tool for analyzing production, this paper will deal with the selection and use of this tool.

THE RIGHT TOOL FOR THE RIGHT JOB

There are many different kinds of production well testers. Testing equipment ranges in production well testers. Testing equipment ranges in price and amount of sophistication from a half-million price and amount of sophistication from a half-million dollars installation with nuclear density gauges to a rusty 5-gallon bucket. There are times when a half-million dollar installation may be an inexpensive way to gather data. However, simplicity should never be confused with obsolescence, nor should sophistication be confused with accuracy. The important consideration is whether or not the test equipment will supply the information the operator needs with a minimum expense over the life of the project. Selection of equipment is very project. Selection of equipment is very important if accurate-reliable test data axe expected. The test equipment used in one area or for one type of production may not be suited for another area or type of production.

When selecting test equipment an engineer should ask the following questions.

Will the equipment measure the amount of total fluid the well will produce during a complete 24-hour period? Will the equipment measure the amount of oil and water and gas per day the well is capable of producing? Can an instantaneous rate check on liquid production be obtained? [This should be accomplished in less than 5 minutes or at most 10 to 15 minutes.]