Artificial Lift Technology: Examining The Gas-Assisted Rod Pump (GARP)

Hannah Hager

Daryl Mazzanti, the Vice President for Operations at Evolution Petroleum is a problem solver. After being fed up by conventional artificial lift technology that couldn’t recover fluids and left a significant amount of reserves in the reservoir, he took the initiative to invent a whole new technology. The Gas Assisted Rod Pump technology (GARP) has the ability to recover reserves left behind by conventional methods. Daryl will speak further about GARP at the upcoming Artificial Lift for Horizontal Wells Summit.

What capability gaps and additional factors led to your invention and development of gas-assisted rod pump technology? How has this new technology increased productivity?

I invented the Gas Assisted Rod Pump technology (GARP®) to recover reserves that are being left behind by conventional artificial lift methods in pressure depletion drive reservoirs in horizontal/deviated wells and vertical wells that are too deep to rod pump or have extended perforated intervals. The reason GARP is effective in increasing production and reserves is that conventional artificial lift methods place the lift equipment many hundreds of feet above the reservoir to prevent wear and tear on down-hole tubulars and to prevent gas and solids interference in the down-hole pumps. Since conventional artificial lift equipment cannot recover fluids that remain below them, these fluids cause a significant amount of back pressure on the reservoir, which equates to reserves being left in the reservoir.

Depending on the reservoir, we estimate between 15—35% or more of the cumulative production to-date is being left behind in these wells. GARP® works by lowering the artificial lift point and effectively reducing the column of liquid that exists above the reservoir. This reduction in liquid column reduces the back pressure on the reservoir which allows more gas and fluid production to flow into the wellbore. Once in the wellbore, gas is used to lift the reservoir fluids above the rod pump in the vertical portion of the well. Gas breaks out of the fluid and flows to the surface, while the low GOR liquid falls and enters the rod pump, which is then pumped to the surface.

One of the issues around developing new technologies is its performance in various well conditions. How adaptable is the GARP technology to varied well conditions? Is there a built-in trouble shooting system – could you describe it?

GARP® is a very adaptable and effective method for horizontal, deviated or vertical wells that have 4-1/2" casing or larger, and have liquid loading issues in which conventional artificial lift technology

is inadequate in recovering the last 15—35%+ of the cumulative production to-date. It will basically work wherever a rod pump system can be utilized and where a relatively small volume gas supply is available (~ 50 MCFD). Troubleshooting the system is the same for troubleshooting rod pump systems which are understood and known.

What are some of the efficiencies created by combining artificial lift technologies, ie., GARP®?

The combination of gas lift and rod pump technology in the GARP® design has many advantages and efficiencies over conventional gas lift and rod pump technology alone. Conventional gas lift technology is very good at lifting fluids from deviated sections and can work at very deep depths. However, since reservoir fluids are raised to the surface, much higher pressure and gas volumes are necessary, which exert significant back pressure on the reservoir which prevents the inflow of fluids from the reservoir, thus trapping reserves in the reservoir. Conventional rod pump technology is the best artificial lift method in lowering the back pressure on the reservoir. It is widely used and understood, and has readily available parts. But as stated previously, it has depth limitations, is prone to gas interference, and has high maintenance costs when the rods and pump are placed in a deviated section. GARP® combines the best of both technologies and eliminates their limitations by placing the rod pump in the vertical portion of the well and significantly reduces the high back pressure associated with conventional gas lift by lifting the reservoir fluids a short distance to the rod pump.

Has the development of GARP led you to develop other technologies? What are some of the patented or patent pending technologies you are currently working with?

The first GARP® installation was designed for casing sizes of 7" or larger. Since there are many hundreds of thousands of wells that have smaller casing strings, I currently have a patent pending (but field tested and proven) design that will work for wells with casing sizes as small as 4-1/2".

In addition to increased yield and addressing downhole equipment placement constraints, what future applications do you foresee for GARP®?

Every day there are more and more horizontal wells being drilled in pressure depletion drive reservoirs. As these wells deplete and liquid levels drops to the depth of the artificial lift equipment, they will begin to experience liquid loading problems. There are also many thousands of wells that have already been drilled that have these same liquid loading issues in horizontal/deviated and vertical wells. This is the future of GARP®, and it looks very bright.

And finally, can you describe why Artificial Lift professionals should come and attend the Artificial Lift for Horizontal Wells Summit and why this event is important for the industry?

For the very fact that artificial lift technology has not had a major leap forward since the 1940s when modern day gas lift valves were invented. Rod pumps are also a very old technology which has not had a major technological improvement in a long time. Now with GARP®, not only has the technology finally come of age for horizontal wells, this new technology will also work in deviated and vertical wells in which conventional artificial lift technology is inadequate.



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