While filling the wiki for some Unusual uses of game mechanisms, Oil Wells and the 10% of pipes mechanisms piqued my interest.
This is not really new but nobody seemed to really dig that and a commenter even said “Not worth the effort”. Oh boy, were they wrong (though obviously, that kinda depend on your definition of “effort”).
Presenting the self-powered Petroleum Well:
Warning: this is a pre-mergedown build. With mergedown, gas weight is going to change, and a slight rework will be needed for Natural Gas / Steam separation. Turns out Steam being lighter with mergedown was a bug, which has been fixed since then.
What makes that possible
Apart from the 10% of pipes mechanism, in pursuit of making the build self-powered, like REALLY self-powered, including the heat source, all pumps and the Oil Well itself, we have to know what we are dealing with.
This rests on the fact that you transform 1kg/s of water at 4.179 SHC into 3.33kg/s of crude oil at 1.69 SHC, or the equivalent of 5.628 SHC. Hotter water means more heat creation.
Since we are dealing with temperatures above 125°C, heat = power, thanks to Steam Turbines.
How does it translate into power? Well, heating 1kg/s water from 95°C to 550°C (number explained later) takes 1 900kDTU/s, while cooling Petroleum from 535°C (again, number explained later) to 125°C takes 2 400kDTU/s. This means we can heat incoming water with outgoing petroleum and still have about 600kDTU/s, or about 600W, left over for operations. That's going to be our absolute limit for everything. It's not a lot, so that means squeezing every last drip of power and optimizing everywhere possible.
The Oil Well itself also produces 33.3g/s of 300°C Nat Gas, which can be used as well. It’s pretty negligible though, as it only accounts for 12kDTU/s when cooled down to 125°C.
Now on the power consumption side, no matter how you build the setup, you need:
- 95% Oil Well uptime => 228W. It’s the average uptime once you factor in backpressure release.
- 32% Liquid Pump uptime => 77W. You could do without with some atmosphere heat exchanger, but since it has to be pumped anyway for a Petroleum Generator, there is no point optimizing there
- 6% Gas Pump uptime => 15W
- Liquid Shutoff => 10W (required to inject 10% packets)
That’s about 330W of baseline power consumption, before you factor in a heat source.
As for heat source, unless you use the Core / a volcano (or other niche heat sources), the obvious choice is a Thermium Aquatuner. This particular variant of the build requires some space materials and the self-powered part isn’t possible without (unless you don’t factor the heat source in), plus a few other things require Thermium anyway (or would need to be more complex to cool elements before pumping them).
That means you have about 270W available for an Aquatuner and the accompanying Tepidizer needed to get rid of excess cooling (since the Aquatuner is used as a heat source, cooling need to be eliminated somehow). Spoiler alert: it’s possible.
A big inconvenience is that, while water doesn’t exchange heat with Natural Gas in the Oil Well internal storage, outgoing crude oil does exchange heat with the natural gas before being ejected. This puts a hard limit on how efficient the setup can get.
Build presentation
A lot of small details need to be done right to have a functioning and optimized build:
- Oil Well return feed: a 10% liquid injector is required especially as the Oil Well backpressure can only be relieved when there is liquid over the input pipe (even if it’s not used): if there is no liquid, the Dupe gets stuck mid-animation and nothing is done.
- Handling Steam that forms on load: while it doesn’t break anything, Steam will form when you reload. A well placed split-turbine can gulp that down for free and generate power in the process. Some automation is required so that Steam is never pumped.
- Extracting all the power: margins are very close, you really need to extract all the heat from the outgoing Petroleum/Nat Gas. This requires 2.5 Steam Turbines. One less turbine to make the build more compact works, but you’ll have a hotter output (around 140/145°C) and not enough power, losing the “self-powered” part.
- Insulating the heat exchanger from the Oil Well: to have water as hot as possible exit from the heat exchanger, the last Petroleum tile should be as hot as possible. This means insulating it from the Oil Well room. A perfect solution is a 1g Chlorine layer below the Mesh Tile (don’t put it in the Mesh Tile, otherwise it will break on load). A liquid-gas bypass could probably have been used as well, but I didn’t try it.
- Heat Exchanger length: one layer is not enough, even with Thermium/Aluminium (unless it's much longer). Three layers is too efficient and loose some power because it pulses Steam Turbines too often. Two layers is a sweet-spot, and that width is more than enough: there isn't a lot of heat capacity to be exchanged here (a lot less than in a 10kg/s Petroleum Boiler)
- Clearance: since Oil Well are in the Oil Biome, just above the Core, clearance will be limited. This is the minimum you can get to keep the build self-powered. You can sacrifice some aspects to gain on clearance, I talk about that later.
Result
With this build, there is about 16% Aquatuner uptime and 3% Tepidizer uptime, which translates to about 220W. That means about 50W of spare power.
In practice, since some heat is transferred to Natural Gas, which is only released every few cycles, the build is slowly loosing power during operation, and there is a spike of power that recharges batteries during and just after Backpressure release. That's why there are several Jumbo Batteries (although that much is overkill, but since they are power positive with Steam Turbines anyway, why not).
This spare power is a nice safety margin, and I don't recommend trying to use it for something else. It would be more trouble than it's worth.
Materials
For this build, I’ve chosen to use Space Materials, which makes it much easier:
- The Aquatuner obviously needs to be Thermium to go up to 550°C. This could be replaced by another heat source pre-space, and remove the Tepidizer in the process (which isn't used all that much anyway).
- Since a Thermium AT is used, it makes sense to use Supercoolant. Obviously, the cooling loop could be Polluted Water as well, at the detriment of power usage.
- The Gas Pump needs to be Thermium as well because Nat Gas is well over 300°C. It's possible to do without by using a Liquid-Gas bypass and cooling Nat Gas before pumping it, but that would alter the design and make it more bulky.
- Everything insulated is made out of Ceramic, in an effort to cut down on space materials
- The Liquid Pump is Thermium, but could be made out of Steel since the Petroleum is below 275°C (at least on this variant, and all variants that are efficient enough)
- The Mesh Tile should be made out of Gold Amalgam to get up to operating temperature faster (lowest SHC)
- Everything radiant was made out of Gold, and could be replaced by Iron or Copper. Note that even using Thermium, 1 layer of that size is not enough to get the build self-powered.
- Anything that overheats should be made out of Steel. Everything that doesn’t is made out of Gold or Gold Amalgam and can safely be replaced by Iron or Copper. Lead should be avoided because a lot of parts go higher than 330°C.
Priming the build
There are a few details to take care when building the setup:
- 1g Chlorine (or any lower) must be injected at the right place. There is space for a vent, but it should ideally be done after there is already an atmosphere in the Oil Well room. Use a combination of Valve, Shut-off and Timer to do that.
- Transitioning from Crude Oil to Petroleum: the Petroleum will push the Crude oil up to the last cell of the first layer, but won’t be able to push the last one. Mopping is required on that last cell. You’ll also need to mop the second layer, otherwise petroleum will stay on top of Crude Oil. This is the reason why the heat exchanger is Dupe-accessible. You’ll also need to separate Crude Oil from Petroleum. A Shut-off left in is a good safety option.
- Until it’s up to operating temperature, an external power source is needed. It can be removed once it’s up to operating temperature, as long as the build doesn't stop. For safety, I encourage you to leave it connected.
- The heat source should be at 540°C for safety before being at operating temperature. Once it is, you can crank it up a bit until your first cell of Petroleum is around 530°C/535°C. Don’t go too high or you’ll have Sour Gas to deal with. While this particular build is at 550°C, other less efficient builds were as high as 570°C to get Petroleum at the right temperature.
What about clearance/space?
If you have a lower clearance from the Core, or want to use less space, there are a few trade-offs that can be made at the cost of performance. Any of those trade-offs will give up the “self-powered” part:
- Reducing to 2 Steam Turbines will have Petroleum / Nat Gas exiting at around 140/145°C, losing about 100W.
- You can actually reduce to 1 Steam Turbine and move the 2 others off-site. This means less cooling used up and slightly more Tepidizer uptime.
- You can sacrifice the insulating Chlorine to gain 2 cells of clearance and make the build easier to prime. Make the Petroleum flow right of the Mesh Tile rather than under it.
- You can sacrifice one layer to gain 3 cells of clearance. Even if you use a Thermium/Aluminium, this will greatly impact performance
- On the other hand, if you have more space, a left-to-right staircase would multiply heat because of this bug, making the build more power-positive.
Other possible builds
While I’m not going to pursue other builds, I encourage you to try variations using the same principle:
- A pre-space build could be made. Edit: I made it! See below in the comments for the Pre-space Petroleum Well. It’s going to be a bit more bulky (especially to pre-cool nat gas so that a Steel gas pump can pump it), and require an external heat source (core, volcano, metal refinery …).
- You can superheat the water much higher (up to Thermium limit) and get Sour Gas. This will result in a very different build.
- As you might have guessed, Electrolyzers are also prone to superheated water, and will delete a fair amount of heat. It remains to be seen if this is more efficient than an ATST.
Conclusion
While it was a fun experiment to design around all those details, I don't think this build will become mainstream. It's a bit complicated, use Space Materials and need some attention for priming.
It can fill a niche where you want to tame a single Oil Well and avoid doing a 3.33kg/s Petroleum Boiler (perhaps on DLC?), but if you want to have 10kg/s Petroleum output , you'll probably be best served by doing some simple Oil Well tamers and a single Petroleum Boiler, rather than 3 Petroleum Wells.
Here is the save file that was used to take the screenshots:
Petroleum Well Demo.sav
