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 Fig. 1). 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.

The accumulated gas in the casing annulus exerts a back-pressure on the down-hole oil formation. This down-hole back pressure (hydrostatic pressure) acts on the oil formation in a manner to prevent or restrict free flow of oil and gas from the formation.When the hydrostatic pressure created by the casing gas is reduced, flow of oil and gas from the formation increases, and thus production of oil and gas increases.
For more than one hundred years, various means of “well head compression” have been used to reduce the hydrostatic pressure by removing the casing gas. Well Head Compression refers to the removal of casing-head gas, and the compression of that gas into the higher pressure flow line. Many types of conventional compressors have been used over the years in attempts to successfully and reliably reduce hydrostatic pressure through removal of casing-head gas. Most of the past attempts were forced-lubrication units that required considerable maintenance, adjustments, and attention. And they were prone to continual failures for lack of adequate and practical technology.

The Basil Beam Compressor (BBC) was developed in the period since 1992 using state-of-the-art materials, seals, and engineering technology. The result is the world’s unique walking beam gas compressor. It’s powered by the force of the walking beam of a typical pumping unit. Power requirement for the BBC 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.

When a BBC 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 BBC begins operation, the casing annulus is full of gas at whatever pressure is at the flow line and the BBC 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.

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 BBC units are the most reliable and efficient beam compressors that have been developed and offered to the oil industry.

The design ambition for the Basil Beam Compressor (BBC) was to deliver a unit that would mount easily on an oil well pumping unit and operate unattended and continuously... maintenance free, adjustment free and lubrication free. To do this the BBC employs proprietary state-of-the-art materials in ways that exploit their particular attributes. For example, BBC cylinders are made of wound-fiber composites that are impervious to hydrogen sulfide (sour gas-H2S) and carbon dioxide (CO2), two corrosive chemical components that are present at many oil wells. At the same time, these cylinders have the strength of steel.
Pistons are made of aluminum, and piston-rods and compressor end-caps are made of special stainless steel. Both of these metals also resist hydrogen sulfide and carbon dioxide. Pistons and rods use seals and wear rings made of proprietary materials developed by DuPont.
The BBC is mounted to a pumping unit by specially designed clamps that prevent the need for welding or drilling on the pumping unit structure (refer to the BBC photographs). The top of the BBC clamps directly to the walking beam. The bottom of the BBC has two methods of being clamped to the pumping unit. (1) if the Samson Post structure is 3-legged, the BBC clamps directly to the third leg with a specially made clamp-plate; and (2) if the Samson Post structure is
4-legged, the BBC clamps to a specially made base-plate that is itself clamped to the base-beams of the pumping unit.

At both the top clevis assembly and the bottom clevis assembly, spherical bearings are used that allow non-restricted, omni-directional movement during operation. These bearings allow the BBC to operate smoothly even if the movement of the walking beam is not perfectly vertical. These bearings also allow the BBC to operate smoothly if the BBC is installed off-center vertically on the pumping unit.
A rod collar assembly at the top of the compressor absorbs side-loads that are impressed on the piston rod during travel of the rod. These side-loads result from the walking beam’s arc of travel, and from possible vertical mis-alignment during BBC installation on the pumping unit. The rod collar assembly prevents side loads from compressing the rod seals, and thus prematurely wearing out the seals.

The gas input and discharge manifold is a unique Y-configuration that maximizes efficiency of the compressor. This maximized efficiency is due to the fact that the check valves are closer to the piston face than would be the case if a standard T-configuration manifold were used.