Electrification .01

A compilation of some thoughts and predictions on the energy industry, particularly decarbonization. I'm painting in broad strokes, and this first piece is meant to ground some of those in a field I'm somewhat familiar with at this point: oil & gas production. Future posts will get into more renewables and even less informed takes on the grid.

Part 1: Produced Fluids to Energy

For oil & natural gas to get from the ground into a combustion engine to release energy (and the emissions that everyone’s talking about), a few things have to happen. Broadly, the process can be split into five steps:

1. Extraction

2. Bulk Separation

3. Transportation

4. Refining

5. Generation

In step one, producers buy or lease promising land, hire a contractor to drill a well, and depending on their game plan, a fracking contractor to frack the well1. The well is shut-in (think a cork in a bottle) and then the producer moves on to step two, which is building out the well pad production facility.

Once the "upstream" facility is built, the well opens up and out comes a mixture of natural gas (mostly CH4, with some other light hydrocarbons), hydrocarbon liquids (think oil, sort of), water, and some trace amounts of nasties like hydrogen sulfide and carbon dioxide. At this stage, the produced fluids aren't particular useful - in many cases, they're corrosive and poisonous. We need each component separated so we can safely and reliably use/or transport them.

Because the actual mixture here can vary a lot depending on where you're extracting from, the exact separation process downstream of the wellhead will vary too. But at a high level the three phases (gas, oil, water) all have very different densities, so most separation is via gravity. Combined fluids enter some kind of drum, gas comes out the top, oil somewhere in the middle, and water drains out the bottom. If you're worried about your oils vaporizing, you can add some heat to remove more gas and "stabilize" the oil. Ultimately the gas goes into a pipeline and the oil and water are stored in tanks and trucked out. This last bit is changing in some states, but we'll get into that later.

Step three is transportation, which is usually handled by "midstream" operating companies. Each produced fluid has it's own end user in mind, and these are often long distances from where the fluid is extracted. We get them from A to B in

(a) pipelines using pressure as a driving force, provided by pumps and compressors, or

(b) tanker trucks

Before that happens though, there are some gas purity requirements that need to be addressed. Common contaminants in natural gas are hydrogen sulfide (poisonous and explosive) and carbon dioxide (also poisonous); both react with water to form acids that eat carbon steel (what pipelines tend to be made of). The specific removal methods aren't particularly relevant, but they generally require a fair bit of energy themselves.

Once the treated, high pressure fluids are in transport, they head to "downstream" operators who handle refinement before selling products to market, Step Four. Natural gas can be broken into constituent parts like methane, ethane, propane etc. each with their own market. Produced oils are similarly broken up and used in industries ranging from energy to cosmetics, and produced water is typically sent to a saltwater disposal facility where god knows what happens2.

Step Five is Generation, where we convert natural gas to useful energy. This (usually) happens in a gas-fired turbine, which converts chemical energy to heat via combustion. The simplified chemistry looks a little like this:

CH4 + 2 O2 → CO2 + 2 H2O + Heat

The turbine converts this heat (and some of the pressure and kinetic energy of the gas stream) to electricity, which gets delivered to the device you're reading this on. And that's how natural gas gets turned into energy3.

Part 2: Emissions

So with a basic understanding of the natural gas to energy process, we can look at where we can try to capture emissions to clean things up a bit. The focus here is on Extraction & Bulk Separation since I’m most familiar with details. The methods here generalize to the other steps pretty well in any case.

In the Extraction and Bulk Separation facilities, the most visible source of emissions are fugitive emissions (e.g. tank vapors), which in most states get sent to a flare and burned. These emissions can be valuable (more CH4 sold is more $) but are near atmospheric pressure and require compression to get back into pipelines. The cost of compression typically outweighs the recovered value, hence the burning4.

In states like Colorado, incentives have shifted such that low pressure gas recovery is now being done. On more recent well pads, producers are going as far as removing tanks all together - liquids are separated, stabilized, and pumped directly to pipelines. The stabilization requires heat input, which is typically gas-fired, and the new pumps and compressors add additional energy load, but it eliminates routine flaring entirely5.

The other big emitters that most are familiar with are the gas-fired engines used to drive compressors and other rotating equipment (pumps, generators, etc) and gas-fired burners. On-site emissions reductions6 are pretty straightforward - replace the gas-fired equipment with electric driven equipment. In practice it can be a huge pain in the ass to get electricity to e.g. bumfucknowhere West Texas, but that’s the quick and dirty solution to gas-fired engine emissions in any one, very specific location.

Reducing emissions in Transportation looks very similar - turn the gas fired compressor (or tanker truck) engines into electric ones, and check your pipelines to make sure you don’t have any holes. I know next to nothing about Refining, but presumably the same lessons apply.

Generation is a slightly different animal. Unfortunately we can’t replace gas-fired turbines producing electricity with electric driven turbines for the reasons I hope are obvious. We could replace them with nuclear powered steam driven turbines, but nobody wants to hear that. Alternatively, we can make them more efficient to reduce emissions per energy produced, and/or capture those emissions directly.

Progress has been made in both directions, and now we're starting to see large scale carbon capture facilities being retrofit to the backend of these power generators. The carbon dioxide-rich flue gas (the exhaust from the gas driven turbine following combustion) is directed through a system designed to remove the CO2 from the exhaust stream before it reaches the atmosphere. Which is all well and good, but now you have a bunch of CO2 that you need to do something with. In general, you can store it underground, make rocks, or use it as feedstock for other processes. Some options make money, some don’t, and figuring out which make sense for who is worthy of a whole other post.

To recap for most of oil & gas, reducing local emissions looks like:

1. Replacing gas-fired engines and burners with electric ones

2. Being diligent in making sure your systems are not leaky. If reducing leaks requires more energy, see (1)

I’m pretty confident that these apply to other industries fairly well, and my key takeaway after putting this to paper was that this is not rocket science. It’s basically all electrification. None of this requires alien tech to accomplish, just a well-executed plan7.

Part of that “well-executed” plan does require acknowledging something I’ve been hinting at in bold above. Replacing a gas-driven motor or burner eliminates the associated emissions from said motor/burner on-site, not overall. The electricity that drives the new motor is produced somewhere, and that somewhere is typically a fossil-powered generating facility. So rather than eliminate emissions, we’ve shifted them up the electric supply chain to the generating facility.

This does not mean electrification is bad or useless. Larger generators have higher efficiencies than small engines, so shifting the power generation upstream does reduce overall emissions per unit of energy consumed. Assuming you replace a gas driven engine with an electric one used in exactly the same way, you will burn fewer fossil fuels to run the electric one and produce fewer emissions. But not zero8.

And while my moralizing in the footnotes says one thing, I’d like to add that I think shifting emissions to central locations is a good thing. Building fewer, larger carbon capture facilities at centralized generating stations (or replacing these large stations with carbon-free ones) seems much easier than building a massive number of smaller facilities.

It does have some interesting implications for the grid at large though, and I’ve so far avoided discussing clean fuels and renewables here. More on that to come.