Visible surface features such as oil seeps, natural gas seeps, provide basic evidence of hydrocarbon generation (be it shallow or deep in the Earth). However, most exploration depends on highly sophisticated technology to detect and determine the extent of these deposits. Areas thought to contain hydrocarbons are initially subjected to a gravity survey or magnetic survey to detect large scale features of the sub-surface geology.

Features of interest (known as leads) are subjected to more detailed seismic surveys which work on the principle of the time it takes for reflected sound waves to travel through matter (rock) of varying densities and using the process of Depth conversion to create a profile of the substructure.

Finally, when a prospect has been identified and evaluated and passes the oil company's selection criteria, an exploration well can be drilled to conclusively determine the presence or absence of oil or gas.

If the criteria for extraction is met, rotary drilling commences to extract the oil. A rotating bit attached to a length of hollow drill pipe bores a hole in the ground by chipping and cutting rock. As the bit cuts deeper, more pipe is added. A stream of drilling mud- a mixture of clay, chemicals, and water is continuously pumped through the drill pipe and through holes in the drill bit. Its purpose is to cool the drill bit, plaster the walls of the hole to prevent cave-ins, carry crushed rock to the surface, and prevent blowouts by equalizing pressure inside the hole. When a drill bit wears out, all drill pipes must be removed from the hole a section at a time, the bit replaced, and the pipe returned to the hole.

When oil or gas is found, the drill pipe and bit are pulled from the well, and metal pipe (casing) is lowered into the hole and cemented in place. The casing's upper end is fastened to a system of pipes and valves called a wellhead, or Christmas Tree, through which natural pressure forces the oil or gas into separation and storage tanks.

If natural pressure is not great enough to force the oil to the surface, pumps may be used. In some cases, water, steam, or gas may be injected into the oil-producing formation to improve recovery.