How exactly is oil extracted from the ground? details...?

Question

is laying underground in pools of oil? does it have to be pumped out? Does it need to be flushed out?

Answer 1

Crude oil does not occur in “pools” underground. Generally speaking, it is found in sandstone deep beneath the ground. Oil and some water, fill the pore spaces in-between the sand grains of the sandstone. Yes they fit in there. But for the oil to accumulate, several conditions need to be met. There has to be some sort of organic source that will produce oil, usually an anaerobic reaction under great amounts of heat and pressure that has to have been deposited below or with the sandstone sediments. A “trap” has to be formed by one: having an impervious rock like shale on top of the sandstone to keep the oil from migrating up, and two: some kind of structure like an arch in the rock (anticline) or a fault face where a large amount of oil can accumulate in one place.

We drill into the top (hopefully) of the trap into the sandstone where the oil has accumulated and cement casing (a 4.5-inch pipe) in place. Because the open space of a drill hole is lower pressure than the oil in the formation, oil flows from the sandstone into the well bore. A series of “pump rods” in the well brings the oil to the surface. In rare circumstances, the pressure relief is enough for the oil to flow out of the well on its own.

Oil flow is enhanced by various operations in the well including “fracturing” the oil sandstone to help the oil flow. Also, water and other agents can be pumped into wells in lower parts of the sandstone reservoir to “float” more oil up and out of the producing well.

Please understand that this is a very simplistic explanation. But it is the best I can do in this limited venue. Pick up a book on Petroleum Geology and learn more. Geology is a fascinating science.

Answer 2

Drilling

The well is created by drilling a hole 5 to 36 inches (127.0 mm to 914.4 mm) diameter into the earth with a drilling rig which rotates a drill string with a bit attached. After the hole is drilled, sections of steel tubing known as casing and is slightly smaller than the borehole to provide an annular for cementing is placed in the hole. The casing provides structural integrity to the newly drilled wellbore in addition to isolating potentially dangerous high pressure zones from each other and from the surface.

With these zones safely isolated and the formation protected by the casing, the well can be drilled deeper (into potentially more-unstable and violent formations) with a smaller bit, and also cased with a smaller size casing. Modern wells often have 2-5 sets of subsequently smaller hole sizes drilled inside one another, each cemented with casing.

To drill the well,

The drill bit, aided by the weight of drill string and drill collars above it, breaks up the earth.

Drilling fluid (aka "mud") is pumped down the inside of the drill pipe and exits at the drill bit and aids to break up the rock, keeping pressure on top of the bit, as well as cleaning, cooling and lubricating the bit.

The generated rock "cuttings" are swept up by the drilling fluid as it circulates back to surface outside the drill pipe. The fluid then goes through "shakers" which strain the cuttings from the good fluid which is returned to the bit. Watching for abnormalities in the returning cuttings and volume of returning fluid are imperative to catch "kicks" (when the pressure below the bit is more than that above, causing gas and mud to come up uncontrollably) early.

The pipe or drill string to which the bit is attached is gradually lengthened as the well gets deeper by s******g in several 30-foot (10 m) joints of pipe at surface. Usually joints are combined into 3 joints equaling 1 stand. Some smaller rigs only use 2 joints and newer rigs can handle stands of 4 joints.

This process is all facilitated by a drilling rig which contains all necessary equipment to circulate the drilling fluid, hoist and turn the pipe, control downhole pressures, remove cuttings from the drilling fluid, and generate onsite power for these operations.

Completion

Main article: Completion (oil and gas wells)

After drilling and casing the well, it must be 'completed'. Completion is the process in which the well is enabled to produce oil or gas.

In a cased-hole completion, small holes called perforations are made in the portion of the casing which passed through the production zone, to provide a path for the oil to flow from the surrounding rock into the production tubing. In open hole completion, often 'sand screens' or a 'gravel pack' is installed in the last drilled, uncased reservoir section. These maintain structural integrity of the wellbore in the absence of casing, while still allowing flow from the reservoir into the wellbore. Screens also control the migration of formation sands into production tubulars and surface equipment, which can cause washouts and other problems, particularly from unconsolidated sand formations in offshore fields.

After a flow path is made, acids and fracturing fluids are pumped into the well to fracture, clean, or otherwise prepare and stimulate the reservoir rock to optimally produce hydrocarbons into the wellbore. Finally, the area above the reservoir section of the well is packed off inside the casing, and connected to the surface via a smaller diameter pipe called tubing. This arrangement provides a redundant barrier to leaks of hydrocarbons as well as allowing damaged sections to be replaced. Also, the smaller diameter of the tubing produces hydrocarbons at an increased velocity in order to overcome the hydrostatic effects of heavy fluids such as water.

In many wells, the natural pressure of the subsurface reservoir is high enough for the oil or gas to flow to the surface. However, this is not always the case, especially in depleted fields where the pressures have been lowered by other producing wells, or in low permeability oil reservoirs. Installing a smaller diameter tubing may be enough to help the production, but artificial lift methods may also be needed. Common solutions include downhole pumps, gas lift, or surface pump jacks. The use of artificial lift technology in a field is often termed as "secondary recovery" in the industry. Many new systems in the last ten years have been introduced for well completion. Multiple packer systems with frac ports or port collars in an all in one system have cut completion costs and improved production, especially in the case of horizontal wells. These new systems allow casings to run into the lateral zone with proper packer/frac port placement for optimal hydrocarbon recovery.

Production

The production stage is the most important stage of a well's life...

more at

http://en.wikipedia.org/wiki/Oil_drillin...

Answer 3

basically: they dig a hole, and use a pump to get the water out. The tech today is astounding, but that is the most basic way, no the most basic way is to shoot at some food.