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Page added on May 7, 2011
Every Barrel Counts: EROEI of Texas pumpjacks
For a long time I’ve been wondering about the amount of effort it takes to obtain energy, whether it’s pumping oil, digging coal or manufacturing solar panels.
In this first post, I’ll explore a simple concept: the Energy Return on Energy Invested (EROEI) of that icon of oil production, the pumpjack. To be more specific, I’ll be looking into a Texas pumpjack: how many barrels does it produce in a day, and how much energy is needed to get that energy out?
I’m at this point only interested in the amount of energy required to make the pumpjack go up and down. Of course it took effort (skills, materials, energy) to discover the oil, drill the well and build infrastructure manufacture, but I’ll leave that for another time.
Returns
So let’s start with the returns. I’m brushing with broad strokes here. According to the Texas Railroad Commission, Texas produced 349 million barrels in 2009 from 157,807 wells. I’m assuming this is not counting the federal offshore fields. Further assuming that ALL Texas oil was produced using pumpjacks, and that there’s one pumpjack per well, each pumpjack produced 2212 barrels in 2009–just over 6 barrels a day. Now, by taking the amount of energy released by burning a barrel of oil to be 6.1 GJ, a pumpjack produces 37 GJ worth of energy.
Investment
Now for the energy invested. I’m assuming from this thread that a typical pump jack uses a 40kW electrical motor, running 24/7. Assuming 100% efficiency (!!!) That’s 60x60x24x40kWe = 3456 MJ or ~3.5 GJ.
EROEI
Simply dividing the former by the latter, the EROEI of a Texas pumpjack is slightly better than 10:1 IF the energy values of oil and electrical energy can be interchanged without loss.
Of course, crude oil is generally not used for heating or electricity production, and electricity is generally not used to drive a car (although that’s changing), so this number can be deceptive–it merely gives an indication.
Conclusion: cut out the middle man?
Concluding this post –and this is me speculating–, it’s interesting to note that a fossil-fueled/coal based power station never exceeds 50% efficiency, excluding transportation losses. Coal is by far the most common source of electricity, I’d guess.
That means at least 7 GJ worth of “coal energy” is needed to produce 37 GJ of “Texas crude energy” in one day. A combustion engine converts chemical into mechanical energy at an efficiency of ~33%, so only around 12 GJ of “Texas crude energy” gets released as mechanical energy by burning 7 GJ of coal, out of an initial 37 GJ.
Which almost means that (and I’m really taking this into the extreme), when you trade in your SUV for a small electric car that runs on coal-generated electricity, you can just as well leave the oil in the ground that would otherwise be used… A.k.a. cut out the middle man… But, as they say, your mileage may vary!
2 Comments on "Every Barrel Counts: EROEI of Texas pumpjacks"
DC on Sun, 8th May 2011 1:35 am
If his calcuations are roughly correct and 10:1 is the ratio, then we have consider what happens next.
The oil has to be then transported to a refinery, in a diesel powered truck. More energy loss,or possibly piped?
Then once at the refinery it has to be well…refined. More energy loss.
Once that happens, another diesel powered truck comes along and takes it back out again, maybe to a gas-station. More loss. It will likely stored in an underground tank where it will have be pumped out again against the force of gravity useing electrical pumps. Loss Again.
Finally, we get to something near the end of the loss chain. It will (possibly) get pumped into a gas-burner of some description, could be an american-built trash bin by GM or Ford, or something really useful like a leaf-blower, but in any event, whatever it goes into will likely have a thermal efficeny less that say 35%. Thats being generous, most gas-powered devices are very inefficent at converting mass to energy. You can bet that in most instances, only 1/4 on average of the gallons will actually end up doing useful work, the rest is just waste heat and of course, pollution, lots of it.
Now there could even more loss. Lets assume some of the remaining energy was used to say, grow pseduo-industrial “food”. Since it takes 10 units of FF energy to make just 1 calorie of food energy, you can begin to see how our system is designed to waste energy. Some end uses may not be so wasteful, this is just an example.
So if we take the 30GJ of energy the well produces, we will still manage to waste a lot more of that before it provides any useful service to end-users. Of course, there is no guarantee the end uses will even be beneficial or even necessary. It could be used to power a hosplital, or a school. It could be used to make novelty rubber dog-shit, or haul obese american children 20 miles a day in chauffred SUV rides to large prison-style US schools where creationist “science teachers” will tell them the earth is flat and 4000 years old. Some of it could end up getting spilled into the enviroment in the very leaky US refinery system, and never get to do any work at all, useful or not.
This is the scope of the problem we have created for ourselves.
David on Sun, 8th May 2011 2:26 am
To DC
Congratulations. Your overview of the production of gasoline from oil is both depressing and hilarious at the same time.
When I read “It could be used to make novelty rubber dog-shit”, I just couldn’t help but crack up in laughter.
It’s so tragic, but the scope of the problem means we will continue to churn out novelty rubber dog shit, right up until the very end.
It makes the Easter Island demise seem quite purposeful and sophisticated.