By Petroleum Technology Transfer Council

Beam-operated gas compressor is profitable in various field applications

A walking, beam-operated gas compressor is a low-cost, reliable solution for gas interference in downhole pumps, replacing expensive two-stage compressors and providing low-cost compression when electricity is absent

 Charles McCoy, Permian Production Equipment Inc., Midland, Texas

 Using the walking beam-operated Beam Gas Compressor (BGC), operators can increase production and reduce operating costs on rod-pumping wells by drawing gas and gas pressure from the casing, alleviating the problem of gas interference in the downhole pump. Operators are utilizing the BGC to force casinghead gas into high-pressure sales lines. Operators find the BGC is the solution to compress casinghead gas in fields where electricity is not available for conventional compression methods. Some operators experience increases of up to 40 bopd with associated gas and compression savings of $20,000 or more. 

  DESIGN AND OPERATION

 Energy from the pumpjack’s normal pumping action is utilized by the BGC. The size of the BGC is configured to compress daily gas production at the operator’s desired casing pressure, within the pumping unit’s normal operating run time. As the walking beam movement pumps the well, the BGC draws produced gas from the casing through check valves and discharges it into the flow line downstream from the pumping tee. The gas rejoins the tubing production and flows to the separator and gas sales line. Normally, the BGC will take gas directly from the casing, but it can be utilized to take gas from the separator and compress it to the sales point. A frequent application is in a low-volume gathering system, where gas from multiple wells can be compressed by joining them together. The BGC is double-acting and does not affect the pumping unit’s counter-balance. The unit can operate in corrosive environments, as well as wet and high BTU gases. It has been installed on virtually every style of pumping unit. In addition to providing economic production increases, the BGC can help operators comply with environmental agencies – it captures and compresses vented gas into the sales line. 

  FIELD APPLICATIONS

 There are three field applications discussed. One is to replace gas-driven, skid-mounted compressors. In this application, the operator saves high rental expenses and the cost of the fuel gas burned to operate the gas engine. A second application forces low-pressure gas into high-pressure sales lines. Operators are using two compressors installed on the pumping unit to provide two-stage compression. Finally, the BGC is being utilized in steam floods, as well as CO₂, to draw gas and pressure from the casing to alleviate interference (gas-locking) in the downhole pump.

 The pumpjack as prime mover for the compressor is not only reliable, but it is energy-efficient and reduces the lease operating expense. BGC installation is simple and can be moved to other wells in the field. Pumpers and lease operators prefer the BGC, because of its simplicity and low maintenance.

  FIELD RESULTS

 Replacing gas-fueled, skid-mounted compressors. At Montezuma Creek, Utah, the BGC was installed on RIM Southwest Corp.’s Anasazie 1 on March 7, 2001. It replaced a conventional gas-fueled, skid-mounted compressor. The BGC reduced casing pressure to <0 psig from 35 psig. Oil production increased to 71 bopd in April from 55 bopd in February. Metered gas production also increased to 63,000 cfd from 50,000 cfd.

 Increased cash flow from the well amounted to $8,531/month, resulting in a unit payout of less than two months. As a result, RIM Southwest Corp. has placed six additional units and is installing a seventh BFC that will be used by three wells. The units have been very reliable, requiring only minor maintenance and upkeep. 

 Two-staging the BGC. In Pecos County, Texas, Endeavor Energy has a facility that is a high-pressure installation, as well as a low-cost gathering system for multiple wells. Two BGCs were installed on Herring 1. One compressor is installed between the Sampson post and the gearbox, and the other is between the Sampson post and the horse’s head.

 Field gas is fed into a manifold and then into the casing of Herring 1 (the casing acts as a scrubber), where the BGCs are installed. The first BGC pulls gas from the casing, compresses it to 60 psig and runs it into the second BGC. The sec-nod (a high-pressure model) then compresses the gas into a high-pressure sales line. This installation takes advantage of not needing an additional motor on location, resulting in energy savings for the lease and simplifying the BGC system. Due to this facility’s success, Endeavor Energy continues to utilize the BGC on other applications in additional fields producing from other formations.

 High sales line pressure. In Kingman County, Kansas, Edmiston Oil Co.’s application is a rod-pumping gas well with a gas engine prime mover. It produces from the Mississippi formation at 4,134 ft. BHP on this well is not sufficient to overcome the high sales line pressure (180 psig), and the company could not produce the well’s full potential.

 Edmiston installed the BGC in 2001 at an AFE cost of $10,000. After installation, gas sales doubled to 140,000 cfd from 70,000 cfd. The BGC system of compression was chosen, because it does not require an additional motor – the pumping unit is the prime mover. This installation accomplished two objectives. First, it forced low-pressure gas into the high-pressure sales line. Second, by relieving backpressure on the formation, the formation was able to produce at its maximum rate, based on the well’s deliverability.

 At the time of installation, gas prices were much lower than at present. However, payout was still achieved within three months. As a result of this installation’s success, the operator evaluated other prospects and installed additional compression systems. As with most projects in the industry, some have shown good increases and some have not been so good, but all have paid out. Edmiston is considering other applications. Not all installations show this much improvement, but gas sales are consistent. 

 Low BHP. In the vicinity of Faskin Oil & Ranch’s Germania 103 in Midland County, Texas, there is low BHP. The well is produced from the Grayburg formation, and Faskin installed a BGC on it in January 2003. Germania 102 had a pump-off controller run time of approximately 12%, with a casing pressure of 52 to 56 psig. With the BGC in operation, the well’s run time increased to 20% to 25%, and casing pressure was drawn down to 0 psig. The result was a 5-to-6-bopd increase in total production, along with the associated gas. 

 Fluctuating sales line pressure. Tema Oil and Gas Co.’s TDU 3-8 is part of a field in Pecos County, a remote location in West Texas. It produces the Devonian formation with relatively low BHP.

 The sales line pressure varies from a normal level of 25 psig, to a high of 40 to 45 psig. When the line pressure went to the high side, half of the production was lost. Oil output would drop from 7 to 8 bopd, down to 3 to 4 bopd. Gas output would drop from 50,000 cfd, down to 30,000 cfd.

 Tema installed the BGC in May 2003, and the production has increased to 11 or 12 bopd, and 50,000 cfgd to 60,000 cfgd. One thing that the operator likes about this system is that the well produces at its maximum rate, and this occurs every day regardless of sales line pressure variations. The firm says that the BGC installation is no problem to look after and maintain. The only routine required of the pumper is weekly lubrication.

 Testing a steam flood application. One operator has utilized the BGC as a backpressure relief test on a steam flood. This field was operating with 90-to-100-psig casing pressure. The BGC pulled the casing pressure down, and the well showed a substantial increase in production and relieved gas interference in pump action. As a result of this test, the operator has installed a complete casinghead gathering system and is in the process of evaluating additional wells to test with the BGC.

  CONCLUSIONS

 The presented cases are applications conceived by operators. While each installation shows a production increase due to reduced backpressure on the formation, they were placed for different reasons. In each case, output increased, resulting in increased cash flow. 

 A BGC installation’s cost ranges from $8,000 to around 13,000, depending on the gas volume, line pressure and the pumping unit on location. It is suggested that before abandoning a marginal well producing against separator pressure, one should take a look at what the well might do producing without backpressure. Some wells have continued to produce at a profit for several more years.  

  ACKNOWLEDGMENT

 This article contains contributions from the following individuals, who offered operating data and installation details: Ken Kundrik, RIM Southwest Corp. (Montezuma Creek, Utah); Dale May, Edmiston Oil Co. (Kingman County, Kansas); Calvin Gene Turner, Faskin Oil & Ranch Ltd. (Midland County, Texas); and Bob Van Husen, Tema Oil and Gas Co. (Pecos County, Texas).

THE AUTHOR
	Charles McCoy is president of Permian Production Equipment Inc., in Midland, Texas. He was educated in mechanical engineering and business administration at Louisiana Tech University. He can be contacted at: cmmccoy@ beamgascompressor.com