Not all refinery processes break hydrocarbons into smaller chains. Some refinery processes involve cracking, but others at lower temperatures are simple distillation.
It is not heavier due to compression. It is heavier due to the molecular weight of long chain hydrocarbons.
Wax, a mixture of relatively longer hydrocarbon chains, in comparison to gasoline, floats on water. Some hydrocarbons float on water, but not others.
Oil is not a single molecular structure. It is dozens and sometimes hundreds of different molecules. It is not simply the same string made longer, but completely different structures such as the before mentioned asphaltenes, paraffins, naphthenes, and aromatics.
The proof is in the results. It seems that the Joint Institute of the Physics of the Earth, Russian Academy of Sciences, Moscow; Gas Resources Corporation, Houston has it figured out.
Yes, but that really isn't related to the discussion of the formation of hydrocarbon molecules in crude oil.
There are lots of other processes as well, desalting, hydrotreating to remove sulfur, reforming to gain octane values, etc.
Some hydrocarbons float on water, but not others.
That was my point. You thought oil formed below and floated up through water. Some of those oil would be sinking not floating. It negates the idea that they were formed below and floated up. In crude oil, this is measured by the API gravity scale. Higher numbers are lighter. 10 is equal to water, lower sinks in water, higher floats.
The proof is in the results.
I agree, exploration on the basis of the biotic formation of oil has produces all the oil we use today. The theory of abiotic oil has produced papers and occasionally cash from the gullible, sometimes that included governments.
Today, there is not commercial oil production not sourced to sedimentary deposits.