Short answers, pulled from the story.
Petroleum is a fossil fuel formed over billions of years from the anaerobic decay of organic materials. Vast amounts of zooplankton and algae settled to sea or lake bottoms where they were covered in stagnant water with oxygen concentration below 0.1 mg/L. Anaerobic bacteria reduced sulfates and nitrates while heat and pressure converted the matter into kerogen and eventually oil through catagenesis.
More than 4300 years ago bitumen was mentioned when Sumerians used it to make boats. More than 4000 years ago asphalt was used in the construction of walls and towers of Babylon according to Herodotus and Diodorus Siculus. The I Ching cites that oil in its raw state was first discovered extracted and used in China in the 1st century BCE.
Petroleum consists of a variety of liquid gaseous and solid components including lighter hydrocarbons like methane ethane propane and butane. The bulk of liquid and solids are largely heavier organic compounds often hydrocarbons containing carbon and hydrogen only. Nitrogen oxygen and sulfur appear in other organic compounds along with traces of metals like iron nickel copper and vanadium.
About 80 percent of world's readily accessible reserves located in Middle East with 62.5 percent coming from Arab five: Saudi Arabia United Arab Emirates Iraq Qatar and Kuwait. Top three oil-producing countries as of 2018 are United States Russia and Saudi Arabia. In 2018 due to developments in hydraulic fracturing and horizontal drilling United States became world largest producer.
About quarter annual global greenhouse gas emissions carbon dioxide from burning petroleum plus methane leaks industry. Along with burning coal petroleum combustion largest contributor increase atmospheric CO2. Atmospheric CO2 risen over last 150 years current levels over 415 ppmv from 180-300 ppmv prior 800 thousand years.