Pumping Unit Powered by Stirling Cycle

Transcription

1 Sucker Rod Pumping Workshop Wyndham Hotel, Houston, Texas September 11 14, 2007 Pumping Unit Powered by Stirling Cycle Bryan Dotson, BP America, Houston TX Loren Madden, WhisperGen Limited, Christchurch New Zealand Joe Rochelle, Rocky Mountain Oilfield Testing Center/DOE, Casper WY

2 The Big Picture.. Gas Well Deliquification Gas wells can be made more productive lifting very low liquid rates.. generally less than 20 BPD. There are a lot (~50,000) of deep gas wells that could benefit from less than 2 HP of lift.. but remote and has to be low cost. An inexpensive, low maintenance, green source of remote power < 5HP will be needed. Hydraulic Horsepower at 50% Efficiency About 51,000 wells (80% of this population) need less than 2 HP at 50% efficiency ,000 20,000 30,000 40,000 50,000 60,000 Well Count Outline Stirling Cycle: Why we re trying it; How it works. RMOTC Test: Well and Pumping Unit; Hookup; Results to Date 2007 Sucker Rod Pumping Workshop 2

3 BP Trial of Stirling Cycle Among solar, wind, geothermal and flowline generation, gas fired generation is attractive for scale up.. we always have natural gas! Stirling Cycle Advantages: Potential for lower maintenance vs conventional generators Heat readily available to condition/dry the fuel gas other uses in cold climates Potential future cost reduction on economies of scale BP selected Whispergen to trial based on successful commercial application in other markets. BP selected RMOTC for the test because of their expertise at trialing new technology, and availability of 1-2 hp pumping unit ( w) Sucker Rod Pumping Workshop 3

4 The Engine Technology Stirling external combustion engine Simple concept with 200 years of history Pistons are powered by nitrogen gas inside a sealed chamber The gas expands and contracts as it is heated and cooled A wobble yoke transfers the pistons linear motion into rotational motion to generate electricity. Cooling water is heated during this process and this is available for other uses (similar to a cogen) 2007 Sucker Rod Pumping Workshop 4

5 The DC Whispergen - Gas Model BP trials based on existing natural gas/propane DC WhisperGen: 24 VDC, 800W generator with fully automated battery charging Gas consumption is.7 cubic meter per hour = 25 cubic feet per hour Electrical efficiency is 11%. If waste heat can be used, total efficiency is 90% (79% thermal recovery) Anticipate new DC gas model to be developed after trials with BP and others 2007 Sucker Rod Pumping Workshop 5

6 RMOTC Test Well The producing well for the test is 58-S-10 located in the SWSE Section 10-T38N-R78W. Drilled in 1994 to a depth of 2184 to test the Niobrara and Steele shale Plugged back and completed in the Shannon formation from 360 to 464 Well has 7 casing set at 530 Well produces with a National 25 pumping unit making approximately 1/2 BPD Test commenced in February Sucker Rod Pumping Workshop 6

7 System Components at RMOTC Pumping Unit 208 VAC 24 VDC To 3Ø 208 VAC Inverter 24 VDC 24 VDC 460 A-Hr Battery Bank Rod Work Well Casinghead Heated Fuel Gas Umbilical 24VDC Whispergen Generator And Heat 2007 Sucker Rod Pumping Workshop 7

8 WhisperGen Heat & Power System Enclosure contains the Stirling generator, the battery bank, the inverters, and the heat trace tank and pump Sucker Rod Pumping Workshop 8

9 DC Buffer Concept DC WhisperGen automatically charges the battery bank at 800W (19kWh / day). Battery bank is sized to supply additional power when demand exceeds generation. The peak load is supplied by the batteries. Depending on electrical loads, battery bank of Ah battery bank (24V) is normal. AC power is available (via an inverter) whenever needed Sucker Rod Pumping Workshop 9

10 Battery Levels 2007 Sucker Rod Pumping Workshop 10

11 WhisperGen at RMOTC This graphic shows the battery current and the Ah pattern during a 24 hr period. 30 Amps or Amp-Hours Battery Current Battery Ah Time, Hours 2007 Sucker Rod Pumping Workshop 11

12 WhisperGen at RMOTC This graphic shows the WhisperGen s power generation in response to the draw on the battery Ah from the 3 HP well pump. Watts Time, Hours Watts 2007 Sucker Rod Pumping Workshop 12

13 Fuel Gas Conditioning Concept is to get gas off a scrubber or casinghead with no free liquids, heat it, and keep it hot to the burner tip. Used micro heat exchanger and heat traced umbilical Sucker Rod Pumping Workshop 13

14 RMOTC Opn s & Mtce Since March 2007 the unit has done 1100 hours and has over 900 starts without any failures. The unit required no maintenance or trouble shooting by the operators on site. One flame detection sensor was replaced after 1100 hours. Maintenance interval for minor components is every 1000 hours. No plugs, filters or oil changes. The core engine requires service after approximately 5000 to 6000 hours. This involves replacement of Wobble yoke bearings, which is typically a half-day task Sucker Rod Pumping Workshop 14

15 Fuel Gas Consumption At RMOTC the 3HP-rated motor was run for 1 ¼ hours per day. System measured fuel consumption has been 33 scf per HP-hr. In winter, the WhisperGen will run an additional 2 to 5 hours to heat the enclosure and therefore maintain a constant temperature to maximize battery capacity and prevent battery bank for de-rating Sucker Rod Pumping Workshop 15

16 Summary and Questions Small deliquification pumps will need low cost, reliable power generation... and gas is always available as a fuel Trial at RMOTC with Whispergen shows there could be alternatives to internal combustion engines... could be attractive today if the waste head can be used... Questions? 2007 Sucker Rod Pumping Workshop 16