P.M. Wilson, Kobe Inc.
From September 1970 to May 1971, prototype jet pumps were installed in five wells in California, West Texas and New Mexico. These five wells were selected to give a wide variation in operating conditions and were used primarily for correlating actual field data with laboratory data and with computer calculated operating charts. During this nine-month period, the cavitation zone of the operating charts was defined and various materials were tested for the nozzle and for the throat of the pump. Three of the test wells used water and two used oil for the power fluid. Depths ranged from 1900 ft to 9500 ft and production ranged from 80 BFPD to 1000 BFPD. In May of 1971, after the jet pump was established as a viable deep well pump, it was formally announced and introduced at the International Petroleum Exposition in Tulsa. By November 1972, 18 months later, approximately 125 jet pumps were operating in the U.S. and abroad. In addition to these 125, another 50 had been installed and later removed-removed because of pumped-off conditions, insufficient surface horsepower, too much gas being produced through the pump or abandonment of the wells. All of these 50 pumps were installed in wells already pumping with hydraulic piston pumps, and as might be expected, most of these piston pumps were the ones experiencing the highest operating expense. But because the jet pump can be made to fit any "Free Pump" bottomhole assembly and because the surface power was already installed, these were convenient wells for operators wishing to try the jet pump. Many of the 125 operating jet pumps were also installed in wells already equipped with hydraulic piston pumps, and they have survived because they have reduced repair costs. Obviously, the jet pump is the simplest pump made for oil wells and its design allows it to tolerate poor quality power fluid, corrosive well fluids and free gas-conditions that lead to high repair costs for positive displacement pumps. Figure 1 shows the producing rates and setting depths of 100 jet pumps operating December 1, 1972. Approximately half of the dots on this chart represent wells in the Permian Basin and the cluster at 9300 ft are wells in Lea County, New Mexico. This chart illustrates the broad application of jet pumping-depths from 1550 ft to 14,750 ft and producing rates from 20 BPD to 1400 BPD. Two pumps not shown on the chart are set at 4500 ft and produce 2700 BPD and 3000 BPD. In Fig. 2 the principal parts-nozzle, throat and diffuser-of the pump are shown. Power fluid (water or oil) at high pressure is supplied to the nozzle which converts the pressure head to a high velocity jet. Pumping action begins when the fluid in the production inlet chamber is entrained by the jet stream emerging from the nozzle. In the throat, the produced fluid acquires high velocity from the power fluid and in the diffuser this velocity head is reconverted to a pressure head-pressure sufficient to move the fluid to the surface. The arrangement of one string of tubing set on a packer in the casing, as in Fig. 2, is called the casing free type system and is the most common type of system used. The parallel type of system shown in Fig. 3 can be used in wells with high gas/liquid ratios, to allow gas to vent through the casing instead of going through the pump.