Discovering, new reservoirs of oil is only the beginning of the story. It’s then the job of a new team of economists, scientists and engineers to decide whether- and how- to go into large-scale commercial production. Once oil or gas have been discovered it has to established how much is there, how much can be recovered, what its quality is and how the oil and gas can be transported safely to a refinery or a terminal. In other words, is the find economically viable? If so, further wells will have to be drilled and production facilities established.
The recovery factor; the amount of oil that can be economically extracted compared with the total amount estimated to be in the ground; varies widely. Twenty years ago a recovery factor of 30 percent was normal. Today the average is about 45 percent. Improved technology is likely to increase this further.
Crude oil is found in underground pockets or traps. Gas and water are generally form in the reservoir too usually under pressure. This pressure is sometimes sufficient to force the oil to the surface of the well unaided and excess pressure may cause problems. In the early stages of production an oil field may have free flowing wells, but as oil is extracted the pressure decreases and pumping may become necessary. Alternatively, it may be possible to increase the pressure by injecting further gas or water into the edges of the reservoir.
In other cases, the pressure is inadequate from the beginning and pumps at the bottom of wells have to be used. The fluid extracted from the well usually contains oil, gas and water. It has to be processed so that the crude oil and gas can be transported by pipeline or tanker.
Crude oil is a natural substance whose composition varies. Even in the same oilfield, where oil is obtained from different depths, it can vary greatly in composition and appearance. It may be an almost colorless liquid or a sluggish, black substance, so heavy that it cannot be pumped at atmospheric temperatures. Generally, however, crude oil look rather like thin, brown treacle.
There is no single solution to the problem of getting oil out. Production and transport methods will depend upon where the oil is found, and in particular, whether it has been found under the land or under the sea. Obviously, it is a lot harder and more expensive to drill for oil beneath the sea then on land.
There are several different types of platforms that can be used, depending on the conditions. Usually, the leg of the platforms must extend at least 30 meters above the surface of the sea, keeping all equipments well clear of the largest waves. For smaller offshore discoveries it is not usually economic to install a platform. In some cases, floating or under water production systems controlled remotely have been developed.
Oil is generally produced in places far away from where it is used: in deserts, frozen wastes, jungles or far offshore. A pipeline hundreds of miles long or super tankers – or both-may be the only way of getting the oil to be refinery where it will be turned into a usable products.
Too reach the edges of the reservoirs; wells are commonly drilled at an angle. It is now possible to drill vertically downward and then outwards horizontally. This can save a great deal of money, as several wells can be drilled from a single point and oil extracted from thin seams of rock.
The main way of moving the crude oil and natural gas from oil fields to refineries are by ocean tanker for crude oil and gas. The engineers who design and construct the pipelines may have to solve problems like with standing currents and corrosion by the sea, passing over a mountain range of river, or keeping the oil moving in sub – zero temperatures.
Ocean tankers are capable of carrying up to 500,000 tones, with a surprisingly small crew of 25 people. The tankers may be up to 350 meters long, and take up to 3 hours to stop moving. This is possible because of the highly sophisticated navigation and safely aids found on modern tankers.