Oil and gas are produced in nearly all parts of the world at different quantities: from small private wells producing 100 barrels a day to huge sharks which produce 4,000 barrels a day; shallow 20-meter-deep reservoirs to 3,000 meter deep wells; in $100,000 onshore wells to $10 billion offshore developments. Despite the differences in the range, the processes stay somewhat similar.
Today, oil and gas is produced in almost every part of the world, from the small 100 barrels-a-day private wells to the large bore 4,000 barrels-a-day wells; in shallow 20 meter deep reservoirs to 3,000 meter deep wells in more than 2,000 meters of water; in $100,000 onshore wells and $10 billion offshore developments. Despite this range, many parts of the process are quite similar in principle. The wellheads manage the flow of oil or gas into the gathering system, they also ensure the safety of the operation. Apart from the wells, there is also the gas and oil separation plant (GOSP).
We usually get a variety of unwanted components like water, carbon dioxide, salts, sulfur and sand. The GOSP actually processes the well flow into clean products such as oil, natural gas and condensates.
If someone’s aiming to make more than a few dozen barrels of oil per day, onshore production would be an economically viable system for them. There are millions of wells that produce oil and gas. A gas gathering networks which can be thousands of wells, hundreds of kilometres apart, feeding through a gathering network into a processing plant.
The image shows a donkey pump equipped with a sucker rod pump, which is associated with onshore oil production, but it is by far not the only way of extracting oil from a non-free-flowing well. Small reservoirs collect their oil in a holding tank, which is then collected and transported to a refinery. In oil-rich areas, on-shore wells can produce up to 1000 barrels per day. The product is sent from the plant by pipeline or tankers. Production may come from many different license owners.
Unconventional reservoirs are those which require special recovery operations outside the conventional practices. tight-gas sands, gas and oil shales, coalbed methane, heavy oil and tar sands, and gas-hydrate deposits are usually found within unconventional reservoirs and as mentioned before they need special treatment to get a useful product. Heavy crude may need some heat and diluents in order to be extracted. Tar sands lose their volatile components and are strip-mined or extracted with steam. Further processing must take place to separate bitumen (a black viscous mixture of hydrocarbons obtained naturally or as a residue from petroleum distillation. It is used for road surfacing and roofing) from the sand. Drilling technology and fracturing have allowed liquids and shale to be produced in increasing volumes allowing the US to reduce dependence on hydrocarbon imports. You can read about offshore production here.