November 20, 2008

Drilling (finish)


Circulating system is very important in drilling operation
The function of this system are to assist rotating system in drilling the formation, provide the equipment which must there, materials and place for working, to prepare, maintain and change drilling mud.

Drilling Fluid

Cool and lubricate the bit and drill string.
Clean the bottom hole
Carry cuttings to the surface.
Remove cuttings from mud at the surface
Minimize formation damage.
Control formation pressure
Maintain hole integrity
Assist in well logging operation
Minimize corrosion of drillstring, casing and tubing.
Minimize contaminant problem
Minimizing torque, drag, and pipe sticking.
Improve drilling rate.

The Main Circulating equipment
Mud Pump
Mud Pits
Mud Mixing Equipment
Contaminant removal

Mud Pump

Mud pumps are the heart of the circulating system. The Primary function is to move large volumes of drilling fluids under high pressure.
There are two basic type of mud pump:

(1) The duplex,

(2) the triplex. The primary distinction is in the number of pistons and how they function.
The double action (duplex) pump is the most common pump in use.

Mud Pits

Large steel rectangular shaped container used to hold and control drilling fluid when it is out of well bore.
Mud pits are all basically the same, but are called “shaker pits” or “settling tanks”.
Steel pits are used because they can be rapidly installed, easy maintained and have a known volume

Mixing Hopper

A funnel-shaped device used when adding in solid materials during treatment of drilling fluid in the mud pits.
The primary type in use is The jet Hopper which operates on vacuum principle.
The mixing hoppers can handle 5-10 sack (up to 800 pounds) of materials per minute.

Mud Gas Separator

Mud gas separator sometimes called the “gas buster”, is mounted on the outside end of the conditioning equipment, next to shale shaker.
Its usually a vertical (sometimes horizontal) tank like container.
Eliminate larger quantities of free gas entrained in the drilling fluid.
Pipe any flammable and poisonous gases to a safe distance away from the rig.

Shale Shaker

The shale shaker is usually mounted on the end of the first mud pits (shaker pits).
Drilling fluid comes directly to the shale shaker from the well bore.
The primary function is to remove larger cuttings and broken formation pieces from the drilling fluid.
This is done by moving the drilling fluid over vibrating screens that separate the unwanted cuttings

The Degasser Is usually mounted on the mud pits. The primary function is to continuously remove entrained gases from drilling mud.
Gasses will reduce drilling fluid density, pump efficiency, decrease the hydrostatic pressure the drilling fluid exert on the wellbore walls, and increase drilling fluid volume.
If great amount of gases are allowed to enter the wellbore, a kick may occur, which can lead to a blow out


The desander consists of number of cone-shaped cylinders that remove smaller solid particles that pass through the shale shaker screens.
The drilling fluid is forced through the cylinder under pressure with the heavier particles being removed and discharged through the bottom by centrifugal force.


The desilter is similar to the desander in operation and function except that desilter can remove very small formation particles from the drilling fluid.


In order to control “kick”, so Blow out Preventers are instaled at the casing head on each rig.
Their fungtion is to control the fluid or gas up to the wellbore
This system acts as very powerful valves.

The BOP stack is located at the casing or wellhead directly under the rotary table on the rig floor.
The BOP stack is an assembly of special devices that may include :

Annular Preventer
Pipe ram preventer
Drilling Spool
Blind Ram
Shear ram
Casing Head

Annular Preventer
The annular preventer is located at the top of the BOP stack assembly
It contained steel-reinforced rubber packing element that closes to seal on drill pipe, kelly, or an open hole
It’s called a “universal preventer”:

Ram Preventer

Ram Preventers close only specific sizes of pipe, tubing or an open hole.
Pipe Ram is to close only on that size pipe for which they are matched.
Blind or Blank Ram is to close only on an open hole.
Shear Rams is to cut the drill pipe and seal the resulting open hole.

Casing Head and Drilling Spool

Casing head is an attachment at the top of casing on which the BOP stack is engaged.
Drilling spool are spacer between preventer. They provide hookups for the choke line (which circulate the “kick” out of the well bore and the kill line which pumps in heavy drilling fluid.

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