What environmental conditions would result in Crude oil being far easier to access than coal?

Question

So, A bit of a long winded explanation:

I am designing a world that is meant to be both nostalgic and alien; A world that is familiar enough at first glance, but has many differences to ours.

One difference I thought of is a difference in steam locomotives; in our world, steam locomotives were mostly built cab-backwards, as it is exceptionally difficult to shovel coal into the firebox of a cab-forwards locomotive. The few cab-forwards locomotives that were built were mostly oil burners, as oil can be pumped in from a rear tender without the use of a shovel.

For this to represent the majority of locomotives, I figure oil would have to be the main source of fuel during the industrial age, rather than coal.

Over the previous 500 million years, what environmental conditions would result in crude oil being generally easier to access than coal?

Or, if there is an easier way to justify cab-forwards steam locomotives dominating the rails during the age of steam, what is it?

And, also, what other differences in the world and society would result from the changes required to make this happen?

Answer 1

The answer is a little more than just geology.

Consider these (Earth) maps:

The first map depicts worldwide coal deposits; the second, worldwide oil deposits; the third, the spread of industrialisation in Europe; the fourth, the worldwide spread of industrialisation by 1850.

Notice the correlations: oil is basically available everywhere the Industrial Revolution didn't happen (the UK, the US, the newly unified Germany). Or conversely, the conditions that allowed for religious, social, cultural, scientific, and technological progress to create the IR happened where oil was scarce to non-existent. It did happen where there was, fortunately, some coal: the UK, the US, Germany.

So what does this mean?

Rather than messing about with geology and oceanography, it would be much simpler, I propose, to place whichever cultures in your world have a similar conglomeration of proper religion, social values, cultural perspective, etc that will lead to rational science and the development of technology to the point where industrialisation can happen in a place where oil is prevalent rather than coal.

Simply that!

As for your subquestion, it might be possible that internal combustion engines are devised sooner; since natural gas often goes along with oil, whaling as an industry would be doomed before it could destroy the world's whale populations (whale oil is what was used for lighting and so forth in the early 1800s); plastics might come along sooner. Certainly the wonder drug that petrolatum (i.e. petroleum jelly) would have been discovered much earlier.

Answer 2

Petroleum has an important property that coal does not: it's a liquid. And when it's kilometers underground, it's under tremendous pressure.

If there's pressure from below (as for instance due to water invading the strata that contain the oil), any crack in the overlying impermeable rocks will lead to the petroleum percolating upward -- through the cracks and into the soil or permeable rock layers above. If all of this happens near the peak of an anticline or dome structure (which are natural traps for oil and natural gas in the real world), near enough to the ground surface, a "seep" will appear above ground.

This is the source of, for instance, the La Brea tar pits -- but the oil that came up there rose slowly enough for the volatiles to evaporate off and leave only the heavier fractions ("tar") to act as a trap for animals over a period of millennia. If the same thing occurred with a higher flow rate and/or lighter crude (say, in Pennsylvania, where early wells often produced gasoline straight from the well head, instead of California), the seep might make large quantities of petroleum available directly at the surface, where one need merely collect it like the water from a spring -- then filter and refine. And again, if the crude is very light, little refinement would be needed to give a fuel much like kerosene (paraffin, if you're a British speaker) or naphtha.

Answer 3

Higher sea levels historically

Most coal comes from land life forms, most oil comes from sea life forms. As summarised by this helpful graph:

That link goes into a short discussion of exactly how complex this process is, but in simple terms - land life->coal, sea land->oil.

Were the sea levels historically much higher, and the land you're currently occupying was ocean until only a few million years ago, your hydrocarbon resources would be more oil than coal.

You'll still need some land life (as you need to, you know, evolve), so you'll still get some coal, but more sea life over the land you intend to mine, more oil deposits.

Answer 4

A lot of natural coal was produced during the Carboniferous era:

The Carboniferous (/ˌkɑːr.bəˈnɪf.ər.əs/ KAHR-bə-NIF-ər-əs) is a geologic period and system that spans 60 million years from the end of the Devonian Period 358.9 million years ago (Mya), to the beginning of the Permian Period, 298.9 Mya. The name Carboniferous means "coal-bearing" and derives from the Latin words carbō ("coal") and ferō ("I bear, I carry"), and was coined by geologists William Conybeare and William Phillips in 1822.

Based on a study of the British rock succession, it was the first of the modern 'system' names to be employed, and reflects the fact that many coal beds were formed globally during that time.

The reason why a lot of coal was formed back then is twofold:

The large coal deposits of the Carboniferous may owe their existence primarily to two factors. The first of these is the appearance of wood tissue and bark-bearing trees. The evolution of the wood fiber lignin and the bark-sealing, waxy substance suberin variously opposed decay organisms so effectively that dead materials accumulated long enough to fossilise on a large scale.

So if your world never develops ligning or suberin, there you have it. But that would means no trees as we know them. Rather, you could have these appearing much later in the history of your world.

Edit: Alexander also suggested in a comment that if lignin-eating fungi evolve earlier, they may prevent a lot of coal formation from the Carboniferous too.

The second factor was the lower sea levels that occurred during the Carboniferous as compared to the preceding Devonian period. This promoted the development of extensive lowland swamps and forests in North America and Europe.

Which resonates with Ash's answer.