The purpose of drilling a developement well is to enable the production of oil or gas .A sample hole in the ground however, would not be much for this purpose.Our drilled hole in the ground however, would not be much good for this purpose.Our drilled hole need to be completed.
The way in which a well is completed can be quite complex ranging from formation to formation.We shall actually consider four major
completion process in this writeup

1.Well tubulars

2.Well head and Xmas tree

3.Tubing Acessories


Wells are drilled in series of stages.Each successive stage is drilled  with drill bit accompanied by a drill pipe.When the hole is created, to prevent caving in and ensure stability casing pipe must be inserted and cemented.The cementing operation is to prevent the migration of salt water to fresh water area.This cemented casing therefore forms a smoothbore through which the next stage of the well would be drilled.

The smallest diameter casing string reaches to and through the oil or gas reservoir.Before the oil or gas can flow from the reservoir to the surface more pipe is installed in the well.This last string of pipe is the conduit through which oil or gas flows up the well.It is known as well tubing.
We use tubing strings in the well for the following reasons

Tubing allows geater flexibility in operations.Additional tools and accessories can be installed in the tubing which allows a wide range of downhole operations to be carried out.
The casing is usually too large to be used as a flowstring.

The casing is usually cemented to the well incase of damage is can't easily be replaced .The tubing on the other hand is easily replaced in case of damag.


Having penetrated this formation and established communication with the reservoir,we have shut it off by cementing the casing across it.It is necessary to re-establish this connection to allow oil and gas to flow into the well and up the tubing.This is accomplished by shooting through the cemented casing string.

The most prevalent method is called Jet perforation technique.This process involves detonation of an explosive charge,the force of explosion causes the casing to open a hole for connectivity.The charges themselves are assembled in a carrying device.The career is then lowered into the well to the appropraitr depth and the charges detonated.

The most common guns are attached to the electric conductor cablewhich is lowered to the well from the winch.When the gunis at the required depth.It is fired electrically by a signal from the surface.An electrical impulse is transmitted down the wire.It initiates detonation of a primer in the shaped charge,which inturn initiates detonation of the main charge.


The well head is the lower most portion of the assombly.it is made up of the annulus.Within the components provision, the annulus is made accessible.Well head components include

  • Casing Head
  • Casing Spool
  • Tubing Head
  • Casing Hangers
  • Tubing Hanger

The chrismas tree is a series of valve above the well head that enables the control of fluid flow.It also permits access into the well tubing during well servicing operations.When drilling exercise is completed,the BOP is usually removed and replaced with exam tree.


In any well, there are number of items of equipment which are placed in hole to provide operational flexibility and safety.For example Packer,sliding sleeves,wireline entry guide,landing nipples etc.
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