why can't they use a fraction of the flaring gas to liquify the rest of the flaring gas? then the liquid gas can be transported just like the oil barrels to the pipeline-connected world
That would be nice but gas liquefaction units were still quite expensive and large, too much so to put one at a single well last time I checked. I haven't been in O & G in a while but I don't think it's changed based on comments elsewhere in this thread.
Are the liquefaction unit's replacement-or-repair costs higher than the value of barrels of liquid gas could generate?
If not what is the timescale to pay itself back?
Would the following alternative work? :
The well delivers barrels filled with oil to the connected world, and thus needs a constant supply of empty oil barrels. Why not fill them with liquid nitrogen (generated at large "economy of scale" liquefaction units at the connected world) and use this to liquefy the gas at the remote well?
Liquification plants typically cost billions of dollars. People are working on things which look like they're more in the 10's of millions range (just eyeballing the machinery and estimating by visible mass of machinery -it's not like they have a website they sell them on), but it's not clear they're cost effective.
Re: your liquid nitrogen idea; "that's not how physics works." Even if you could store liquid nitrogen in oil barrels (you can't) ... how does that help you?
uhm, it helps by providing a cool heat bath to pump the gas heat into? the idea is not to store liquid nitrogen in the barrels, but merely transport them to onsite storage?
Edit: it's not surprising that LNG liquefaction plants cost on the order of say billions of dollars: by economy of scale one is driven to build extremely large plants. This does not mean smaller (but less efficient) liquefaction plants at much lower costs are impossible, but it does mean those smaller plants don't reach the same efficiency as the bigger ones... (my refrigerator is condensing and freezing water from air...)
If you pump natural gas through liquid nitrogen you get ... slightly colder natural gas. Try again. In fact, please go look at how LNG liquifaction actually works. It's not something that works on a small scale, which is why I posted you a link to the smallest scale LNG plant that actually exists in the corporeal world.
It's not like people haven't thought of these things before. Thermodynamics is well understood.
>If you pump natural gas through liquid nitrogen you get ... slightly colder natural gas.
I am not proposing to bubble raw natural gas through liquid nitrogen.
>It's not like people haven't thought of these things before. Thermodynamics is well understood.
I don't claim to be the first to come up with the idea of using liquid nitrogen to liquefy raw natural gas. I am entirely open to the idea that using liquid nitrogen to liquefy RNG is somehow uneconomical or infeasible. I was hoping to get a more constructive reply: not references of how expensive or hard a smaller scale liquefaction plant is, but rather papers detailing why specifically using a heat exchanger with liquid nitrogen is infeasible, if as you say "It's not like people haven't thought of these things before."
What is raw natural gas? Predominantly methane, and some slightly longer alkanes, with impurities (H2S, CO2, N2, He,...) see [1].
What are the atmospheric boiling points of the alkanes? see [2]:
alkane, boiling point:
methane -183 °C
ethane -183 °C
propane -190 °C
butane -138 °C
pentane -130 °C
hexane -95 °C
heptane -91 °C
octane -57 °C
nonane -51 °C
decane -30 °C
undecane -25 °C
dodecane -10 °C
eicosane 37 °C
triacontane 66 °C
Observe that the lowest boiling point of the alkanes (the fuel in natural gas) is for propane at -190 °C.
The atmospheric boiling point of liquid nitrogen is −195.795 °C [3], wich is colder than the boiling point of any alkane!
What does this mean by definition? that a balloon filled with gaseous alkanes, when submerged in a heat bath of liquid nitrogen, and left to equilibrate temperature, will fully liquefy.
>Thermodynamics is well understood.
^ indeed
(This is my first order interpretation, assuming the mixing entropy does not decrease the boiling point of a mixture of alkanes, if however this is the case, I would like to see an explicit reference to a paper describing this for alkanes.)
So essentially heat exchangers and a supply of liquid nitrogen should be able to liquefy raw natural gas.
Now what about the economics of having to generate liquid nitrogen?
Let's take a step back: domestic natural gas pipelines connected to the gas grid doesn't contain liquid but gaseous natural gas. So at some point the liquid natural gas is expanded to a gas, and this absorbs heat at a low temperature. (I don't know at what point in the distribution chain this happens, but it necessarily happens somewhere.) This is the ideal point to colocate the liquid nitrogen generation plant: use the evaporation of LNG to gaseous natural gas to help the heat pump liquefy air/nitrogen, so the energy required to liquefy nitrogen is largely recycled.
The storage of liquid nitrogen at the gas well should be an entirely solved problem: at the exact sciences campus (de Sterre) of the Ghent university, at the solid state research block, there is a large (fenced off) tank of liquid nitrogen, and once in a blue moon a tank wagon comes to refill it...
There are actually liquid nitrogen services used in well servicing (I saw them but never inquired what they were for) and they were on the scale of a medium-sized service truck - so in theory, what you're proposing should be possible.
My guess is that in practice, it's not profitable given the current price of natural gas and the difficulties of keeping liquid nitrogen cold - the smaller the container, the shorter the time it can economically stay liquid. So you'd need either pretty bulky equipment that needs to be moved once the gas at a well runs out, or you'd have to spend an awful lot of the energy from the gas keeping your N2 cold during transport. Which even if it is profitable on paper, might not survive contact with the field - oil leases are not controlled environments, and Murphey's law is out in force out there in a way that can be easily underestimated.
