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Transcript of Oil Extraction
Geologists use seismic surveys to search for geological structures that may form oil reservoirs.
The "classic" method includes making an underground explosion nearby and observing the seismic response that provides information about the geological structures under the ground
However, "passive" methods that extract information from naturally-occurring seismic waves are also known.
The drill bit, aided by the weight of thick walled pipes called "drill collars" above it, cuts into the rock
Drilling fluid, a.k.a. "mud", is pumped down the inside of the drill pipe and exits at the drill bit. Functions of the drilling mud include cooling the bit, lifting rock cuttings to the surface and preventing destabilisation of the rock in the wellbore walls
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 pit.
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, remove cuttings from the drilling fluid, and generate on-site power for these operations.
Completion of well
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 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 production stage is the most important stage of a well's life; when the oil and gas are produced. By this time, the oil rigs and workover rigs used to drill and complete the well have moved off the wellbore, and the top is usually outfitted with a collection of valves called a Christmas tree or production tree.
As long as the pressure in the reservoir remains high enough, the production tree is all that is required to produce the well. If the pressure depletes and it is considered economically viable, an artificial lift method mentioned in the last slide can be employed.
Types of Wells
wildcat wells are those drilled outside of and not in the vicinity of known oil or gas fields.
exploration wells are drilled purely for exploratory (information gathering) purposes in a new area.
appraisal wells are used to assess characteristics (such as flow rate) of a proven hydrocarbon accumulation.
production wells are drilled primarily for producing oil or gas, once the producing structure and characteristics are determined.
Abandoned well are wells permanently plugged in the drilling phase for technical reasons.
Cost of a Average Oil well
The cost of a well depends mainly on the daily rate of the drilling rig, the extra services required to drill the well, the duration of the well program (including downtime and weather time), and the remoteness of the location (logistic supply costs).
The daily rates of offshore drilling rigs vary by their capability, and the market availability. Rig rates reported by industry web service show that the deepwater water floating drilling rigs are over twice that of the shallow water fleet, and rates for jackup fleet can vary by factor of 3 depending upon capability.
With deepwater drilling rig rates in 2015 of around $520,000/day, and similar additional spread costs, a deep water well of duration of 100 days can cost around US$100 million.
With high performance jackup rig rates in 2015 of around $177,000, and similar service costs, a high pressure, high temperature well of duration 100 days can cost about US$30 million.
Onshore wells can be considerably cheaper, particularly if the field is at a shallow depth, where costs range from less than $1 million to $15 million for deep and difficult wells.
The total cost of an oil well mentioned does not include the costs associated with the risk of explosion and leakage of oil. Those costs include the cost of protecting against such disasters, the cost of the cleanup effort, and the hard-to-calculate cost of damage to the company's image.
Thank you for Watching
Manahil and Iqra
The road towards
The well is created by drilling a hole
into the earth with a drilling rig that
rotates a drill string with a bit
After the hole is drilled, sections of steel pipe (casing), slightly smaller in diameter than the borehole, are placed in the hole. Cement may be placed between the outside of the casing and the borehole known as the annulus. The casing provides structural integrity to the newly drilled wellbore