Deep Well Pumping Problems

The problems of deep well pumping are many and varied. The troubles encountered not only vary from area to area, but from field to field in a given area, and even from well to well in a given field. The first problem of pumping a deep well is to design an installation that will reduce either the desired amount of fluid, or the maximum amount of fluid, as the case might be. For a given size pump, the rod stress or hydraulic pressure increases with pump depth and the cost of lifting a barrel of fluid increases accordingly. We normally think of operating a sucker rod at a maximum stress of 30,000 pounds per square inch. The well is frequently equipped with 5 l/2-inch tubing and l-inch rods. An 8200-foot string of 3/4-inch rods suspended in air will stress the top rod to 30,000 pounds per square inch. For the same stress, tapered strings of 7/8- and 3/4-inch, and 1, 7/8 and 3/4-inch can be about 10,000 and 11,000 feet in length, respectively. How is it then possible to pump wells deeper than 10,000 feet? The acceptable life of a rod depends not only on the maximum stress but also on the range of stress. We therefore permit an increase in the allowable stress, but reduce the stress range by using a smaller pump. Desired production is obtained by increasing the stroke length. Forgetting the design for the present, let us assume that we have a well quipped with a sucker rod pump and discuss some of the problems that may occur. The hydraulic long stroke pumping unit and the hydraulic pumping system will be discussed later.