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Little Pump That Could

Hydraulic Submersible Pump Tackles Low Pressure, Low Fluid Volume Gas Wells
[Print Article: March 2008, by Elsie Ross] IN HIS WORK AS A DRILLING AND service rig hand and later as a consultant, Clayton Hoffarth had a lot of opportunities to see what worked -- and what didn't -- when it came to technology.

Over time, Global Energy Services Ltd.'s chief technology officer became convinced he could build a better pump, and four years ago he had a chance to do just that. Employed as a completions and workover consultant by Trident Resources Corp., he had encountered the problems of continuing failures with downhole pumps in the company's Mannville coalbed methane wells.

Setting to work, Hoffarth came up with the design for his now patented Activator Hydraulic Submersible Pump (HSP), which addresses the main problems of existing artificial lift solutions: gas lock and solids. The pump, which as of mid-January was installed in 35 wells in Western Canada, "will do everything I would have ever liked to have had to work with," he says.

While originally designed for coalbed methane wells, the HSP has been successfully installed in conventional natural gas wells with low pressure and low rates of water. "We shine at low volume," says Hoffarth.

As producers strive to squeeze out the last remaining gas in maturing reservoirs of the Western Canadian Sedimentary Basin, they are faced with the challenge of low pressure wells in which existing technology -- such as plunger lift and velocity strings that require energy from the well -- does not work as well.

"When there is not enough energy to lift that water, our pump comes in," says Farhan Farshori, Global's vice-president of corporate development. While electricsubmersible pumps (ESPs) can do much the same job as the HSP, they are not designed to handle low or varying fluid rates.

The HSP pump fills a niche that is currently not being addressed -- wells with between 0.01 cubic metres and 24 cubic metres (150 barrels) per day of water -- says Farshori. "It's a huge opportunity for us and we address it."

The pump is designed to fit 4 1/2-to seven-inch casing and it has been deployed in depths of up to 1 650 metres. In the HSP, the flow of hydraulic oil to the

bottomhole pump determines the cycles of the pump while the speed with which the oil is sent dictates the frequency of each cycle. A single joystick in the surface unit determines the amount of hydraulic oil sent to the bottomhole pump, which in turn determines the amount of fluid produced.

Within the pump, a 10-slot self-flushing sand screen filters out large particles of frac sand, coal and cement. The screen is a 1.3-metre tube of 1.5-inch outer diameter and 0.01-inch spiral slots. The intake ports of the pump are located within the screen and the fluid exhausted from the cooling chamber back flushes the screen with each stroke. Smaller particles that pass through the screen are pumped through the pump into the production string and out of the well.

A hydraulic flow control valve in the surface equipment can be easily adjusted to almost instantly increase or decrease the volumes of water produced. That's a major advantage over other forms of artificial lift that may require a service rig, a complete reinstallation or a crew to make changes to accommodate fluctuating volumes, notes Farshori.

That ease of use extends to installation of the HSP, which runs on three coiled tubing strings: two hydraulic power strings and one production string. The use of coiled tubing eliminates the need to thread piping, enabling the pump to be installed and running within half a day. A single coil tubing unit can deploy or pull the pump and all three strings in one run.

"It's a real good little system," says Darrell Eagles, a production engineer with Devon Canada. "You just set it and forget it."

The HSP is simple, portable, environmentally-friendly and "the price point is pretty good," says Eagles, who has used it to dewater shallow gas wells in the W4 area of eastern Alberta. The low-pressure wells, 250 to 1 250 metres deep, produce about 10 cubic metres of water per day. Most of the wells in which the pump was placed averaged about 1 100 metres.

He also appreciates the HSP's reliability; one pump has been in a Devon well since April 2006. The only problem Devon encountered was in an admittedly corrosive environment which ate away the coil tubing.

Eagles, now working in the W5 area, would like to see the pump adapted so that it can operate in deeper wells, which could also include tight gas wells. "If it went deeper, I'd be the first guy to sign up for it," he says.

The HSP's positive displacement design is ideally suited to horizontal and deviated wells, and with no reciprocating or rotating rods it provides greater reliability. One pump, for example, has been operating for more than two years at an 86.5 degree angle to the vertical in an Alberta horizontal coalbed methane well. Its small size (about 15 feet long) also enables the HSP to land in a shorter straight section of a well.

Another fan of the system is Jim Kelly, operations manager for CBM operator Ember Resources Inc., who describes the pump as "very good." It has operated reliably downhole for more than two years in an Ember horizontal well in a Mannville pilot project in the Mellodale field near Barrhead, Alberta.

The HSP has "infinite variability within the design so we can essentially slow it down to close to zero and up to 16 cubic metres a day," says Kelly. That range of pump speeds is not available in any other style of pump, he notes.

And while there are other pumps that can be adjusted from surface, the range and the way in which that is done are much more involved, according to Kelly. "This is as simple as moving a hydraulic control valve; we can change the speed rate within minutes."

Global's goal is to be involved in every aspect of dewatering for marginal and old gas wells, a market Hoffarth describes as "amazing." The next step is a gas compressor (patent pending) at the wellhead, which will be available in the second quarter of 2008. Operating off the same engine as the bottomhole pump, it will provide a cost effective solution for production from conventional gas wells, the company says.

In some wells, the pressure on a gas line on the surface sometimes restricts the flow of gas from a well, says Farshori. "We are combining a compressor right at the wellhead with our hydraulic drive; you will not only get the water, you will literally suck out the gas," he says. "This is the ultimate final solution [to prolong the life of old wells]." Global already has clients ready to put the system to test in the field.

The company is also about to roll out a portable HSP system designed to compete with swabbing trucks that periodically are called in to swab out small "nuisance" amounts of water (perhaps six bbls of water per month) in Belly River and Horseshoe Canyon wells in Alberta that do not require the permanent installation of the pump.

In a typical swabbing operation, water that accumulates in a well eventually blocking the perforations is pulled up past the perforations. "Our clients are telling us when they swab, the water gets pushed past the perforations and can sometimes damage the formation and decrease the flow of gas," says Farshori.

With the Global system, the coil unit comes out, puts the HSP pump in the ground and pumps everything off through the production tubing, then pulls it out and goes on to the next location. Operators can sign up for a program in which Global will bring the unit in whenever it is required.

The cost of a permanent HSP is related to depth and is extremely cost competitive when all the costs associated with alternative systems are taken into account, according to Hoffarth. Those costs include the cost of trucking the equipment, downtime when a pump fails, bringing in a service rig to adjust the pump volume and the cost of methanol to ensure a pump doesn't freeze in the winter.

Farshori, though, acknowledges the company needs to bring down the cost if the pump is to be considered an option for marginal gas wells with production of 50 thousand cubic feet per day or less and it is tackling that challenge.

The next challenge for Hoffarth will be meeting the needs of clients who are asking for a pump that can handle higher dewatering rates of up to 50 to 100 cubic metres per day.

An operator in the Barnett Shale in Texas with horizontal wells at a depth of 3 500 metres is interested in the HSP but there is a limitation on the volumes of water it can handle at that depth, says Farshori. To meet the requirement, Global plans to redesign its pump technology to enable it to handle larger volumes at deeper depths. It is currently working on plans for a pilot project using the new pump in the Barnett Shale by the middle of this year.


Farhan Farshori, Global Energy Services, Tel: (403) 243-0820, E-mail: [email protected]


    An Activator HSP is lowered downhole. About three dozen of the Global Energy Services' pumps have been installed in Western Canada.

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