CASING ACCESORIES
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Transcript of CASING ACCESORIES
WHOISTOT
Guide Shoes:
Is attached to the first length of casing to be lowered into the hole to guide the casing into the borehole, around obstructions
WHOISTOT
FloatCollars:
Permit literally float into the borehole, by virtue of being partially empty. It is a back pressure valve which is closed by the outside fluid column, thereby preventing entry of the fluid as the casing is lowered into the hole.
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Centralizers &Wall Scratchers:
To ensure a reasonably uniform distribution of cement around the pipe.To obtain a competent seal all the way around the casing and with the adjoining formation.
Wall scratchers are mechanical wall cleaning devices, attached to the casing , that abrade the hole when worked by reciprocating or rotating.
Centralizers serve to prevent differential sticking
This helps to provide a more suitable surface for the cement
to bond to.
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Cementing Head
Provides the union for conecting the cementing lines from the cementing pump to the casing.Makes it possible to circulate the mud in a normal manner.And displace the cement without making or breaking any conections
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CementingIs the process of mixing and displacing a
cement slurry down the casing and up the anular space
Bonds the casing to the formation.Protects the producing formations.Helps in the control of blowouts from high-pressure zones.Provides support for the casing
Prevents casing corrosion
Forms a seal in the event of kick during drilling.
Cementing also helps in the following ways:
Cementing procedures are classified as primary or secundary.
WHOISTOT
Primary CementingIs performed inmediately after the casing is
run into the borehole.
Single-stage cementing through casing (normal displacement)
There are modified techniques for special situations:
Multi-stage cementing (wells having critical fracture gradients or requiring good cement jobs on long strings)Inner string cementing through drillpipe (for large diameter pipe)
Annulus cementhing through tubing (surface pipe or large casing)
Multi string cement (small diameter pipe)Reverse circulation (critical formations)Delayed setting (critical formations and to improve placement)
(during drilling)
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Primary CementingCIRCULATION
SPACER AND GROUT
PUMPING DISPLACEMENT DISPLACEMENTJOB
COMPLETED
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THE SINGLE -STAGE
The bottom (red) plug, is immediatly followed by the cement.
Two plugs are usually contained in the cementing head to facilitate the
operations.
The top (black) plug, which is solidly constructed, is released when all the cement has been pumped.Pumping is stopped as soon as there ia a positive indication (pressure incrase)
MULTI -STAGETwo or more separate sections behind the
casing string, usually for a long column that might cause formation breakdown if the
cement were displaced from the bottom of the string.
Multi-stage tool is then opened hydraulically by special plugs, and fluid circulated through the
tool to the surface
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Secondary CementingPlugging to another producing zone
Plugging a dry holeFormation «squeeze»Squeeze used to:Supplement or repair a faulty
primary cement jobRepair defective casing or improperly placed perforations
Pumping rate is slow enough to allow for dehydration and initial setting.is continued until the desired «squeeze» pressure is reached.
(during production)
Minimize the danger of lost circulation zonesIsolate a zone prior to perforating or fracturing Abandon permanently a non-producing or depleted zone
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Cementing ClassificationsThe burning of blends of calcareous and argillaceous materials.
This process is called «Portland cement»
Used for oil well cementing carry special API classifications, based on depth and temperature ratings
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Cement Additives
Reduce slurry density and increase slurry volume (Lightweight additives)Increse thickening time and retard setting (Retarders)Reduce waiting-on-cement time and increase early strengthIncrease slurry density to restrain pressures (Heavyweight Additives)
The preparation and supply of compositions tailored to suit the requirements of any well condition. Additives are used to tailor the systems.Additives are used to:
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Mixing and Other Surface Equipment
Proportions and blend the dry cementing composition with the carrier fluid. Control of mixing spped is regulated by the volume of water forced through the jet and by the amount of cement in the hopper.Te
cementing unit is an assambly of special pupose pumbs