With more and more emphasis on reducing the operating costs for beam units, operators are examining several approaches to cut costs. One of the biggest costs in beam unit operations is the electrical power cost.
Controlling pumping units to adjust to the optimum counterbalance will reduce the electrical bill. Several pumping untits have been checked with a PC software program (POWER), which allows the operator to determine how far out of balance the units are and what it will take to properly balance them. Properly balanced pumping units will result in electrical savings both in demand and in consumption, thus reducing total electrical costs.
Examples from several fields are provided illustrating actual power costs and the reduction in expenses that occurred.
The first approach in determining whether the pumping unit requires re-balancing or motor downsizing is to conduct a power survey of the field. When the POWER software first became available, it was used on several individual wells to determine if the unit had an out of balance problem or the motor was too large. The "POWER" program requires actual data. Two current and three voltage probes are connected to the incoming electrical lines. During two strokes of the pumping unit, power and current data is stored in computer memory for interpretation. The power data is converted to gear box torque and if out of balance condition is observed the program recommends the counterweight adjustment required to achieve a better balance. The actual time to measure these values is small, but all the data is necessary to properly interpret the condition of the well. If the well is operated with a pump-off controller, one must determine the condition of the well for the majority of the run time, since pumping conditions may vary widely from first coming on to just before pump-off.
The first small field surveyed consisted of 17 producing wells in the Waddell Field, near Crane, Texas. Production depths ranged from 2,635 m to 2,937 m (8,700 to 9,700 ft.) and all wells were equipped with beam pump units. The Waddell field has a history of high gas-oil ratios, which has caused some lifting problems in the past. Incomplete pump fillage is not uncommon since, in some cases, the tubing intake is located above the perforations, due to the presence of liners and open-hole completions.
Direction of pumping unit rotation was checked to determine the direction that resulted in lower electrical power consumption. In some cases, changing the direction of rotation did help reduce the electrical power costs and the rotation was permanently changed to take advantage of the savings. Other work was performed to determine which tap on a high-slip motor is best, and whether direction of rotation makes a difference in operations. Preliminary recommendations are to operate in the high-torque mode and rotate counterclockwise, unless rod overloading becomes a problem.
Table 1 lists the wells in the Waddell area and data gathered from the field survey.
