$/hp for incremental motive power
$/hp for incremental motive power
(OP)
Quick check here, gents, if you have a chance. I'm not very familiar with the gas compression market, so it's conceivable that I'm way off base.
I was asked how much annual value a single incremental horsepower has to someone with a ~650hp gas compression rig, assuming we're moving gas with 900btu/cf worth $10/MBTU.
My answer was "anywhere from $10 to $10,000, depending on the application."
My reasoning for the bottom end of the scale was that someone might not be able to utilize that extra hp even if it was available, so while it wouldn't be worthless, it would have relatively little value.
My reasoning for the top end of the scale was that if you assume that the guy who owns the compressor gets a full $10/MBTU for the gas, and that he is working with an inlet pressure of 0psig and an outlet pressure of 1000psig, he can probably move another 3350CFD with a value of $10k/yr. (subtract a tiny bit for fuel)
So how far off does that seem from the truth (especially the second bit)?
I was asked how much annual value a single incremental horsepower has to someone with a ~650hp gas compression rig, assuming we're moving gas with 900btu/cf worth $10/MBTU.
My answer was "anywhere from $10 to $10,000, depending on the application."
My reasoning for the bottom end of the scale was that someone might not be able to utilize that extra hp even if it was available, so while it wouldn't be worthless, it would have relatively little value.
My reasoning for the top end of the scale was that if you assume that the guy who owns the compressor gets a full $10/MBTU for the gas, and that he is working with an inlet pressure of 0psig and an outlet pressure of 1000psig, he can probably move another 3350CFD with a value of $10k/yr. (subtract a tiny bit for fuel)
So how far off does that seem from the truth (especially the second bit)?





RE: $/hp for incremental motive power
Adding hp can either lower suction pressure or raise discharge pressure. If lowering suction pressure results in moving to a better place on a particular well's IPR curve then sales will increase and suction and discharge pressure will go up a tad, then rate will decrease, the pressures will go down, etc. until the well finds a new equilibrium at a lower suction pressure, higher discharge pressure, and higher flow rate (this is the best possible scenario).
If the additional hp is needed to overcome discharge pressure then the suction pressure has been creeping up to match the reduced flow caused by the hp being used to overcome discharge pressure increases and you'll be lucky to see anything.
The magnitude of any of these numbers is very much specific-well dependent. In San Juan Basin Fairway CBM wells, I've seen 2 psi reduction in wellhead pressure increase flow rate 2 MMCF/d. I've also seen a 10 psi reduction causing a 1 MMCF/d decrease (long story, but true).
In deep, pore-volume-storage (i.e., conventional) reservoirs I've seen a 2-5 psi decrease in wellhead pressure make zero improvement in immediate rate, but flatten decline a couple of points (a major win).
Man, I'm sorry, but there just isn't a simple answer to this question.
David
RE: $/hp for incremental motive power
RE: $/hp for incremental motive power
I design compressors to run about 80% of derated hp at the design conditions. I rarely ever see any uplift from decreasing the suction pressures just to grab some of that extra hp (and consistently running over 90% has been shown to increase downtime). It sounds like the gains (if any) will be in reliability. That can often be enough to justify major expenditures, but if your machine is already running over 95% up time then the payout will be tough.
David
RE: $/hp for incremental motive power
The ones that scare me the most are the guys with software fixes or increased monitoring or tighter emmission controls. They claim a few percentage points of improvement. Well, on a 600HP unit, naw. If you can get 2% on a fram 5, I'd listen. But on a 600HP field unit it would cost more to maintainthe new system.
Zadas04, I use to be an 80% load guy (Warren Petroleum Engineering Manual), now I'm a 95% load on the new stuff. The change is I do all the maintenance and inspections now because I get all the operating help and budget I need. I like this model versus overbuy and scrimp on maintenance model I use to have to live in.
RE: $/hp for incremental motive power
I'm a blood-guts-and-feathers wellsite kind of guy and well perfomance changes from minute to minute. I really hate when a compressor goes down on high manifold pressure or under speed because the well just decided to give me a bunch more gas too fast for the suction controller to operate. Also, no one (especially not me) ever gets the design flow rate "right" on a well just getting compression. Being content to have average fleet hp utilization in the 70-80% range and not being upset by 60% significantly improves up time.
David
RE: $/hp for incremental motive power
To further show my ignorance, what's a Fram 5? (Frame 5 gas turbine with a missing e?)
RE: $/hp for incremental motive power
request references (corporation and contact person & number) for previous purchaser's of the kit.
consider a purchase agreement similar to an experiment - that is, install the system on 1-engine and if system works as specified, you buy it. if system does not perform as specified, then return to seller at no cost. the only cost incurred by user would be installation & minor material costs.
several years ago, a simmilar purchase agreement was made with an ignition system provider to be used on a CB GMV-10 naturally aspirated ICE. the offer by supplier of ignition system was that by simply installing the ignition system (including plugs), the emissions rate would be reduced by 30%, but fuel consumption would either remain the same or it will slightly increase (<2%). so, ignition system installed, test was done, and we bought the ignition system. surprised everyone. we ended up transferring the ignition system to a turbo-charged Clark TLA-10 where the benefits were greater.
yes, my guess is Frame 5 as 2% hp is a large value.
something to ponder . . .
good luck!
-pmover