A procedure is described that allows an operator to identify artificial lift wells which are operating inefficiently. A logical sequence of steps is presented for acquiring performance data such as casing annulus fluid level, casing pressure, bottomhole pressure, dynamometer analysis and motor power/current. The criteria to be used in determining the system efficiency and the causes of inefficiency are presented. Following the logical methodology will reduce the time and effort required to perform a well analysis and will result in a complete understanding of the well's performance. Understanding a well's performance is necessary before an operator can modify an artificial lift system and improve performance efficiently. A field case on a well in which the electricity cost was reduced by one-half and the mechanical maintenance cost was reduced by twothirds is presented.
During depressed oil price markets, the need to increase oil production, reduce operating costs and increase net income requires an integrated analysis of the pumping system. The analysis should include the performance and interaction of all the elements: the reservoir, the wellbore, the gas separator, the downhole pump, the rod string and pumping unit in beam pumped wells and the prime mover. Such system analysis can be undertaken efficiently using portable notebook computer based data acquisition systems in conjunction with appropriate transducers and software1. Field experience undertaking such analysis in many wells has resulted in the development of a procedure which insures that a good understanding of an artificial lift system is obtained with a minimum of cost and effort. The object of this paper is to present this methodology to improve artificial lift operations. The end result of such system analysis should be the complete understanding of the performance of a given well so that changes to reduce operating costs and increase production can be implemented.
In general the following steps should be undertaken:
Analyze the well's inflow performance to insure that the maximum production is obtained.
Analyze each well's overall electrical efficiency to identify wells needing improvement.
Analyze the performance of downhole pump and downhole gas separator.
Analyze the mechanical loading of rods, gearbox and beam in beam pump systems.
Analyze the performance of the prime mover.
Portable notebook computers, state of the art sigma-delta Modulation15 analog to digital converters and modern sensors allow the acquisition of pressure, load, acoustic signals, acceleration, motor power, motor current and other data with greater accuracy than previously possible. Modern sigma-delta analog to digital converters have a resolution better than one part in a million at data acquisition rates commonly used in oil field analysis. Modern Windows software (with help files) simplifies the acquisition and the analysis of well performance.
The steps to be followed in defining the performance of a system should result in the maximum of information with a minimum of time and effort. Having access to information about the well's characteristics, electrical and mechanical equipment, completion data and well tests in a computerstored database facilitate time efficient analysis.