Functions of Oil Well Casing: Safeguarding Extraction Processes and Environmental Integrity

The oil well casing plays a pivotal role in the secure and effective extraction of oil and gas. Essentially, it consists of a series of steel pipes that are inserted into the drilled wellbore, serving various crucial purposes:

  1. Wellbore Stabilization: Casing is indispensable in preventing the collapse of the drilled hole under the pressure of surrounding rock formations. By offering a robust and rigid support structure, casing ensures the avoidance of cave-ins and provides a stable pathway for drilling and production activities.
  2. Contamination Prevention: Acting as a protective barrier, casing isolates the oil and gas reservoir from the surrounding rock and groundwater. This barrier prevents the contamination of produced hydrocarbons by undesirable fluids and safeguards freshwater aquifers from potential pollution.
  3. Well Pressure Control: Casing plays a crucial role in managing the high pressures encountered during drilling, production, and well workover activities. By directing the flow of oil and gas upward and maintaining pressures within safe limits, casing minimizes the risk of blowouts and other well control incidents.
  4. Selective Production Facilitation: In wells with multiple hydrocarbon-bearing formations, casing facilitates selective production from specific zones. This is achieved by using smaller-diameter casings (liners) within larger ones, effectively isolating different producing intervals and controlling fluid flow from each zone.
  5. Conduit for Production Equipment: Casing serves as a conduit for production tubing, downhole pumps, and other equipment essential for extracting and transporting oil and gas to the surface. It also provides a secure foundation for attaching the wellhead and Christmas tree equipment at the well’s top.

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Oil & Gas Well Casing – VDO Training

There are several articles discussing about casing design and we would like to share you this excellent VDO training in this topic “Oil & Gas Well Casing”. This VDO contains the basic over view of casing starting from surface to production section.  You will see nice illustrations which help you get clearer picture on this topic and we also add full VDO transcripts to provide assistance to some learners who cannot catch the content in this VDO clearly.

Oil & Gas Well Casing – VDO Transcript

oil-Gas-Well-Casing

By the time the crew drills the well to depth, it usually has several strings of casing in it. These strings are called conductor casing, surface casing, intermediate casing and production casing.

Notice that cased well looks something like a telescope pulled out of full-length but it is as the crew drills the well deeper, the size of the whole and the size of the casing gets smaller in diameter. Almost always, the drilling contractor cannot begin drilling at the surface and go all the way to total depth in one step.

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Basic Understanding of Oil Well Casing and Tubing

Oil well construction requires several casing string to reach a planned depth of a well therefore we will discuss about the basic of each casing string used in the oil wells.

Basic-Understanding-of-Oil-Well-Casing-and-Tubing

In this article, we will cover the following strings;

  • Conductor Casing
  • Surface Casing (Structural Casing)
  • Intermediate Casing
  • Casing Liner
  • Production Casing
  • Production Tubing

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