Introduction To Oil And Gas Exploration And Production

Oil has been used for lighting purposes for many thousand years. In areas where oil is found in shallow reservoirs, seeps of crude oil or gas may naturally develop, and some oil could simply be collected from seepage or tar ponds. Historically, we know of tales of eternal fires where oil and gas seeps would ignite and burn. One example 1000 B.C. is the site where the famous oracle of Delphi would be built, and 500 B.C. Chinese were using natural gas to boil water.
But it was not until 1859 that "Colonel" Edwin Drake drilled the first successful oil well, for the sole purpose of finding oil.

Today oil and gas is produced in almost every part of the world, from small 100 barrel a day small private wells, to large bore 4000 barrel a day wells; In shallow 20 meters deep reservoirs to 3000 meter deep wells in more than 2000 meters water depth; In 10.000 dollar onshore wells to 10 billion dollar offshore developments. Despite this range many parts of the process is quite similar in principle.
Oil flows out of the the wellheads. They feed into production and test manifolds. In a distributed production system this would be called the gathering system.
Next there is a processing system, often called the Gas Oil Separation Plant (GOSP). See Oil and Gas Processing Plants for details of major such units
While there are oil or gas only installations, more often the wellstream will consist of a full range of hydrocarbons from gas (methane, butane, propane etc.), condensates (medium density hydro-carbons) to crude oil.
With this well flow we will also get a variety of non wanted components such as water, carbon dioxide, salts, sulfur and sand.
The purpose of the GOSP is to process the well flow into clean marketable products: oil, natural gas or condensates. Also included are a number of utility systems, not part of the actual process, but providing energy, water, air or some other utility to the plant.

Onshore production is economically viable from a few tens of barrels a day upwards. Oil and gas is produced from several million wells world-wide. In particular, a gas gathering network can become very large, with production from hundreds of wells, several hundred kilometers/miles apart, feeding through a gathering network into a processing plant.
Heavy crude may need heating and diluent to be extracted, tar sands have lost their volatile compounds and are strip mined or could be extracted with steam

Offshore, depending on size and water depth, a whole range of different structures are used. In the last few years, we have seen pure sea bottom installations with multiphase piping to shore and no offshore topside structure at all.

page revision: 5, last edited: 13 Mar 2015 13:43

A Barrel Full