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I've heard a lot of people push for natural gas as a fuel for generating electrical power. However, oil is said to be a very dirty fuel. Aren't oil and natural gas harvested from the same sources? The cost of each can of course vary, but to what extent will total oil production and total gas production be linked in the future? If countries take measures to make oil more expensive and natural gas cheaper, won't they cancel out?

Bonus question (if applicable): Is there any company that only produces natural gas, not oil?

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tl;dr: Oil wells produce some natural gas, and natural gas wells produce some oil, but natural gas wells tend to be more "specialized," meaning that as their quantity and productivity increases, the linkage between these two fuels diminishes.

This answer looks mainly at oil and gas production in the US (since that's what I'm more familiar with, and the U.S. leads global petroleum and natural gas production as of 2018).


Productivity by well type

The EIA provides data on production rate of oil and natural gas wells. The report explains how wells are classified as either a "gas well" or an "oil well":

EIA designates wells as either oil or natural gas wells based on a gas-oil ratio (GOR) of 6,000 cubic feet (cf) of natural gas to 1 barrel (b) of oil (cf/b) for each year’s production. If the GOR is equal to or less than 6,000 cf/b, then we classify the well as an oil well. If the GOR is greater than 6,000 cf/b, we classify the well as a natural gas well.

6000 cf of natural gas and 1 b of oil have roughly the same energy content -- about 1800 kWh. The FAQ in the report explains a bit more about how these wells are classified:

Does a natural gas well remain a natural gas well during its entire production history?

In this report, we sometimes classify a well as a natural gas well in one year and as an oil well in another year, and vice versa, depending on a well’s gas-oil ratio. We used this approach because the respective volumes of liquid and natural gas produced by a well can change significantly during its production history.

I downloaded the data and converted the numbers to terawatt-hours (TWh) to make it easier to compare:

Productivity by well type

Three important things stand out from this chart:

  • There are more gas wells
  • More fossil fuels are produced by gas wells
  • The ratio of gas:oil in oil wells is greater than oil:gas in gas wells

This last point essentially means that gas wells are "better" at doing their main job, than oil wells are.

Most "new" natural gas is coming from shale gas wells

Data on production of natural gas in the US from various sources is available here from the Energy Information Agency.

I downloaded the data and put together this chart showing total historical withdrawals of natural gas, along with what is vented and flared*:

Historical natural gas withdrawals by source in the US, 1968 to 2018

Modern shale gas wells (using hydraulic fracturing, or "fracking" methods) produce a higher proportion of gas compared to traditional methods. Growth in this area is massive over the last two decades, meaning the ratio of oil:gas production is falling.

However, this growth in natural gas tends to replace coal production, while total oil production continues to increase

From EIA's International Energy Statistics:

Global primary energy production by source


What is venting and flaring, and why is it done?

From the EIA:

In areas where natural gas is produced at oil wells but is not economical to transport for sale or contains high concentrations of hydrogen sulfide (a toxic gas), it is burned (flared) at well sites. Natural gas flaring produces CO2, carbon monoxide, sulfur dioxide, nitrogen oxides, and many other compounds, depending on the chemical composition of the natural gas and on how well the natural gas burns in the flare. However, flaring is safer than releasing natural gas into the air and results in lower overall greenhouse gas emissions because CO2 is not as strong a greenhouse gas as methane.

Over time, as natural gas has become a more important fuel, the quantities which are vented and flared have diminished, even as total production increases (source):

US natural gas vented and flared

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They are inherently linked. Every oil well produces some gas. A few gas wells produce only methane and ethane but a majority also produce some propane, butane, and heavier hydrocarbons. It depends on whose definition you are using as to when LPG ( liquid petroleum gas) becomes an oil component. And oil wells normally produce more gas and less oil as they age and are eventually plugged. Another way to look at it as both are hydrocarbons and the temperature determines if the hydrocarbon is in a gas phase or liquid phase.... Bonus answer : There is no production/drilling company that produces only gas or oil. The closest may be coal bed methane but any company that I know that produces this gas also has other types of wells. Bonus answer to question not asked : Nearly every well is drilled in hope of finding mostly oil as it is more valuable. To the extent that a well that produces nearly all gas may be plugged and not produced and considered a failure ( depending on several factors such as location.).

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  • I actually think this answer is better than your other one :). I found some data showing the relationship, which I added to my answer. Looks like with the explosion (no pun intended) in shale gas wells, the ratio of gas:oil from a "typical" well is increasing, meaning the link between the two fuels is not as strong as it once was.
    – LShaver
    Jan 2 '20 at 22:21
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Simpler answer: In the context of the question, gas and oil are two names for the same thing, hydrocarbons. Whether a hydrocarbon is a gas or liquid depends on the temperature. Methane "natural gas" ( one carbon atom) is a liquid below -259 F. Ethane ( 2 carbons) liquid below -127 F. Propane (3 carbons) liquid below - 44 F. Butane ( 4 carbons) liquid below 32 F. Pentane ( 5 carbons ) liquid below 87 F. etc. As hydrocarbons come out of a well they are always a mixture and also include water and sand. Many other things may also be produced by a well like hydrogen sulfide , in many wells . And things like elemental mercury , in a few wells around the world. These additions do not affect whether a hydrocarbon is a gas or a liquid.

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  • Thank you. So is the premise of the question (gas being cleaner than oil) wrong?
    – UTF-8
    Jan 2 '20 at 17:27
  • @UTF-8 that's a question that's still widely debated, but probably it's wrong. Take a look at this related question: How is Natural Gas more sustainable as fuel than Gasoline?
    – LShaver
    Jan 2 '20 at 18:59
  • Methane has a higher ratio of H to C than any other hydrocarbon ,so per pound of fuel it produces less CO2. Jan 3 '20 at 20:08
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Geologically and by origin, yes, they are linked. Politically they've started to split. Its use is much less detrimental environmentally than oil or coal - it burns clean and is nontoxic. And it was termed an important “transition fuel” by President Obama as part of his administration’s clean energy goals. Gas companies glommed onto to that by marketing it as a “green” fuel, and in public campaigns seemed to distance themselves from oil, despite often having stakes in both markets. The discovery of shale gas has been the most important catalyst in bringing natural gas back strongly the US energy mix from its height in the 1990’s. The development of transportable Liquid Nitrogen Gas (LNG) has enabled it to be an export product. Likewise, many cities are reinvesting heavily in gas distribution infrastructure, swapping out entire systems of iron pipes to new plastic materials.

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