Walking Beam Compressors

Walking beam gas compressors are not a new idea. There are examples of early beam gas compressors in petroleum museums. Those early efforts were cranky and inefficient and, finally, the idea fell into disuse.

About 1975, the rising price of crude reawakened interest, especially in Bakersfield - where thick California oil was being held back by gas pressure. The academic community set to work and came up with designs that were mostly modifications of existing compressors built for other purposes. Though the need was strong, excessive wear, constant lubrication requirements, and high maintenance discouraged further development. Again, the beam compressor idea, though good, was virtually abandoned. With new space age materials that didn’t exist in the 70’s and 80’s, a proper beam compressor designed specifically for this particular job has been designed and built. This one needs no lubrication, no periodic adjustments, no maintenance, it’s impervious to carbon dioxide and hydrogen sulfide, and has exceptionally long lasting wear characteristics.

Oil wells that use pumping units to artificially lift oil from the well are also wells that generally produce natural gas in addition to oil. When the ground oil-formation releases oil into the well bore, the formation also releases natural gas into the casing annulus. The annulus is the volumetric space between the inside diameter of the casing and the outside diameter of the tubing that is located within the casing. The tubing is the string of pipe through which the sucker-rod string operates the down-hole oil pump attached to the bottom of the tubing-string (see pic, click to enlarge). The down-hole pump forces the oil up through the tubing to the well-head, and then into the flow line away from the well-head. The oil formation pressure moves oil from the formation into the well-bore, specifically into the casing annulus at the location of the down-hole pump.

As oil is released from the formation into the well bore, gas is also released from the oil formation. This released gas will fill the annulus all the way up to the surface casing-head. When the casing-head gas pressure becomes equal to or exceeds the flow line pressure, the gas leaves the casing-head and enters the same flow line as does the well-head oil. (Figure 1)

Walking beam compressors, while in use now for years have often been saddled with maintenance and other performance issues that make them a risky investment. In recent years, new technology and operating strategies have been developed that easily overcome previous detriments to walking beam compressors.

One particular walking beam compressor, the Oil Flow Compressor (OFC®) was developed in the period since 1992 using state-of-the-art materials, seals, and engineering technology. The result is the worlds unique walking beam gas compressor. It's powered by the force of the walking beam of a typical pumping unit. Power requirement for the OFC is approximately 3 to 7 horsepower. Both maintenance free and adjustment free, replacement of seals is typically required, at minor cost, about every eight (8) months of continuous operation.

An oil-production chart for a well generally follows a curve like this: (Figure 2)

When an OFC® is installed at a well, an initial flush production of oil and gas occurs. This flush increase is due to the fact that when the OFC® begins operation, the casing annulus is full of gas at whatever pressure is at the flow line and the OFC® removes the gas at a rapid rate of discharge. As the gas removal occurs, oil is released from the down-hole formation by the sudden and significant drop in hydrostatic pressure.

A typical oil discharge chart looks like this: (Figure 3)

After the flush-production period, the oil flow settles out at a different production level. The extent of the new production level is primarily a function of the permeability and porosity of the oil formation and, of course, of the efficiency of the walking beam gas compressor. The OFC® units are the most reliable and efficient beam compressors that have been developed and offered to the oil industry.