Abstract

This paper describes how the mini computer was applied to develop a well information database and manage test data to optimize a large number of artificial lift wells in the Swift Current area. Selection of candidate wells for dynamometer/fluid level surveys, optimization procedures, and results of equipment changes are discussed.

Introduction

Artificial lift optimization may be described as the procedure of making changes necessary to obtain the maximum production rate concurrent with the lowest possible lifting cost. Knowledge of both well potential and capacity of the lift system is required before optimization decisions can be made. Inflow capability of a pumping well is commonly estimated by measuring the annular fluid level, calculating a subsurface pressure, and applying a productivity relationship between pressure-drawdown and production. Dynamometer surveys are used to determine equipment loads and evaluate displacement performance of the lift system.

The benefits of an optimization study include the identification of: inappropriate sized lift systems, improperly balanced pumping units, abnormal pumping conditions or mechanical problems, leaking tubing strings, and well inflow problems.

Mobil Oil Canada, with the assistance of Tri-Ener-Tech Petroleum Services Ltd., designed and conducted a lift system optimization study beginning in May 1988 on several hundred wells located in the Swift current area of South Western Saskatchewan.

The desktop computer proved to be an invaluable tool for gathering, managing and reviewing the vast amount of information to successfully complete the study within a short time frame of five months.

DISCUSSION
BACKGROUND

Just less than 600 wells on artificial lift are operated by Mobil in mature waterflood fields surrounding the Swift Current area. While some of these wells are equipped with electric submergible and rotary pumps, beam pumps account for almost 90 pee-cent of the lift systems. Typical beam pumped wells produce 20 m3/day fluid with a 90 percent water cut, from a depth of 1000 metres. Aside from the high wateroil- ratio, pumping problems in one or more of the producing fields include: sand laden fluid, corrosive fluid, and gas interference in same instances. Prior to the optimization study there was only limited fluid level and dynamometer history on most wells which did not have a high equipment failure frequency.

DESIGN

Pre-study meetings between Mobil and Tri-Ener-Tech were held to discuss objectives and formulate a strategy La yield the quickest possible turnaround of information to identify the most low-cost production gains, Owing to the large number of wells and the need for identifying the most cost-efficient production gains within a short time frame, the study was designed as follows:

  1. Construct a computerized well information database to provide quick access of information needed to process survey results and later assist in evaluating optimization changes, Details of the completion, lift equipment, and production rated were required in this database.

  2. Narrow down the number of dynamometer surveys based on a review conducted by the field engineering std(f to select only those wells either experiencing equipment problems, or suspected l)f having the best potential for production gains. Also identify wells requiring only fluid level surveys, or fluid depression tests, to evaluate productivity.

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