Low Cost Rod Pumping Management in Kern River Field
Authors: Randle J. Seth 
Published: December 2007

This paper describes a low cost rod pumping management system that has increased the productivity of well monitoring, dynamometer analysis, and team decision making in the Kern River Field. Well monitoring productivity has improved with a contractor's once a month dynamo meter survey program first developed in the Duri Field in 1989. Current improvements to this earlier program include the collection of environmental compliance information, digital data acquisition, and direct transmission of the data from the field to an office computer database. Using a Windows based software application on a computer network to analyze the dynamometer surveys, operators and engineers have dramatically improved the productivity of data analysis over looking at paper printouts. These improvements in technology were implemented by a process based operations team, consisting of a select group of operators and an engineer, focused solely on well pulling and rod pump optimization.

Introduction

Various monitoring methods, including "visual fluid pounds", "pump checks" and dynamometer analysis, have been used to maximize the performance of the rod pumping lift system of Kern River wells. These monitoring methods, carried out by both company field operators and contract well crews, ensure that wells are kept "pumped off". In Kern River, a pumped off condition means that the pumping capacity is set so that the well bore fluid level is kept at the pump intake depth.

The simplest monitoring method, called a "visual fluid pound", consists of watching for a pumping unit's bridal to vibrate on its stroke cycle. A visual fluid pound can occur when the down stroking plunger hits a fluid level in the pump barrel. This collision sends a vibration up the rods to the bridal. In this way, a visual fluid pound can show if a well's pumped off condition from where the vibration occurs after the unit begins its down stroke. Field operators usually record the pound at 0, 25, 50, 75, or 100% with 100% representing the start of the down stroke.

Although this method is simple, it also has many limitations due to its subjective nature. First, the vibration can be dampened as it travels up the rods if the vibration is very small relative to the length that the vibration must travel up the rods. On shallow Kern River wells, visual fluid pounds are often difficult to see on a slow stroking unit. This effect is exaggerated when pump fillage is close to 0 or 100% because the unit is at the slowest part of its stroke as it begins to change direction. Other mechanical vibrations, such as a polished rod striking the horses head, can also lead to deceptive assessments of a visual fluid pound.

A second monitoring method is commonly called a "pump check" in the Kern River Field. A pump check consists of stroking the pumping unit with its flow line closed in order to measure an increase in the tubing pressure, typically with an analog gauge. An increase in tubing pressure is usually interpreted as a sign that the pump is in good condition. On the other hand, a tubing pressure that does not increase usually indicates that there is a hole in the tubing, a grooved plunger, or a worn barrel, ball, or seat. In such cases, the well is identified to be pulled for mechanical reasons.

A pump check also has many limitations. First, this test assumes that the flow-line valve is not leaking. Another problem can occur if the barrel is worn in only part of the stroke because the pump may hold pressure at one place in the stroke, but slip in another. Therefore, a pump check must be tested through out the stroke of the unit to ensure pump integrity. Another disadvantage is that contract crews qualitatively interpret the pressure measurement to assess the pump but do not provide the company with recorded data to support their assessment. Pump checks also require a two person contract crew and costs around $16 per test.

A third monitoring tool is dynamometer analysis. P. 833^