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Oil Well Drilling

The oil well has a long history that dates back to at least 347 CE. The Chinese and Japanese were the first to drill for oil, which they used primarily to produce salt and to use in lamps. In Japan, petroleum was known as burning water. Early wells in Asia were drilled using bamboo and extensive systems of bamboo pipes and storage tanks were devised to maintain constant supplies

In current times, drilling relies on the oil rig. An oil rig is a mobile, self-powered conglomeration of tools used in drilling. The components of an oil rig can be divided into six major categories.

  1. Power System – Diesel motors are generally used to create electricity in generators. Electricity is then used to power everything else on the rig, including the drills.
  2. Derrick – This is the support structure that holds the drilling apparatus. These have to be tall enough to allow new sections of drill pipe to be added to the drill as other sections sink below the ground surface. Standard derricks can accommodate up to three section of 10 meter long pipe. Some can accommodate four.
  3. Mechanical system
    • Hoisting components are used for moving about the heavy pipe and controlling the drill angle
    • Rotating components can be broken down into three sections.
      1. The turntable or rotary table drives the rotating motion of the drill.
      2. The drill string is comprised of 30 foot sections of pipe to which the drill itself is attached
      3. Drill bits come in many materials including tungsten carbide and diamond for cutting through tough rock layer. Drill bits are exceptionally expensive.
  4. Casing – This is the large diameter concrete tubing that lines the drill hole and prevents it from collapsing. These are usually poured on site, though pre-poured versions are available.
  5. Circulation System – This system consists of apparatus to both pump water into a drill hole and to extract it from the drill hole. Water is used to lubricate and cool the drill bit as well as dissolve and carry away dirt and other debris. Mud that is generated in this process is used in conjunction with the blowout preventer to maintain downward pressure on the well.
  6. Blowout preventer – These are pressure release valves designed to seal drill lines and relieve pressure when necessary to prevent oil from gushing from the hole uncontrollably.

It is a common misconception that drilling occurs all in one step when in reality it occurs in stages. In general, drilling is performed to a certain depth and then cement casings are poured before drilling begins again. This repetition of drilling and casing occurs several times to ensure the drill hole does not collapse and to help prevent blowout. Blowout occurs when oil under pressure is ejected from the bore hole. Periodic cessation also is necessary in order to remove mud and other debris that has built up and may be required if rock type changes and a different drill bit is needed.

When drilling crews get close to the depth at which oil is expected, they perform the process known as completion. When the crew reaches completion depth, the bottom of the drill hole is perforated using explosive charges. The final lengths of piping are then pushed into the well and the Christmas tree is cemented to the top. A Christmas tree is a multi-valved structure that resembles a Christmas tree and which allows for the control of oil flow from the well.

The flow of oil in most wells needs to be started, usually through the addition of acid or other chemicals that dissolve the rock in which the oil is trapped. Explosive charges are also used to break apart rock layers and start the flow of oil. Once oil begins to flow, the rig is removed and production and storage equipment are put into place.