Abstract

Using capital and power cost as measures, a comparison is made of the two most popular forms of artificial lift: beam pumps and submersible pumps. After discussing the pumps and submersible pumps. After discussing the difficulties involved, and simplifications required in making the comparison, limits of operation are established and a common range of depths and rates suitable for both techniques is found. Within this range many sets of equipment are sized, using computerized selection programs, and capital and power costs are calculated. The results are compared and a total '10 year cost' is estimated for each unit. Capital costs are found to be higher for beam pumps, but power consumption is less. Charts summarize the findings for easy reference.

Introduction

It is a complicated task to compare different forms of artificial lift. Many of the parameters defining an equipment selection are not continuous: discrete jumps have to be made in component sizes if the output performance is to be increased or decreased. This means that one technology may be better than another at one particular output level, only to lose out at a slightly higher level. In addition to the above, in real-life comparisons one single factor is liable to swamp all others in any particular case, making details such as relative efficiency and cost quite irrelevant.

Nevertheless, engineers are always seeking general principles, resigned to the fact that they often will not work in principles, resigned to the fact that they often will not work in practice. It is in this spirit that the investigation was practice. It is in this spirit that the investigation was undertaken, and the main approach was to simplify and hold constant as many variables as possible. In this manner general trends should be revealed, that might offer insight into underlying influences.

The comparison between beam and submersible pumps is probably the one most frequently made in the field of probably the one most frequently made in the field of artificial lift: the two technologies share quite a wide range of application where both systems perform well. At the top of the power range, submersibles have the edge in sheer horsepower and production rate capability, while at the low end, as submersible efficiency falls off, the beam pump reigns supreme. In between, particularly when reduced hole size forces the use of smaller diameter, less efficient submersibles, it is often not obvious which system is best.

The two fundamental parameters that represent the task of lifting fluid from an oil well are the depth from which the fluid must be lifted and the rate at which it must be pumped. The two together define the required hydraulic pumped. The two together define the required hydraulic horsepower, if certain simplifying assumptions are made:

Power Depth × Rate × Constant Horsepower Feet of Lift x Barrels per Dayx 7.376 E-6

So it is possible to make a comparison over a range of depth and rate values which both types of pump can achieve. To judge the results, the engineer usually looks at the capital cost and operating cost, all else being equal. In our case, energy cost was chosen, rather than full operating costs, because maintenance and repair vary so much from field to field.

Based on the above, it was decided to compare beam and submersible pumps in 5-1/2" (140 mm) casing, a common size in many parts of the world, observing the restrictions imposed by the casing internal diameter. Using the simplifications detailed under 'Assumptions', the limits of depth and pumping rate for each system were established and hence the shared range of application was derived. Over this common range capital cost (new list prices) and energy cost were compared.

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