🟥 Cement Plug and its functionality in drilling
The mitigation of operational problems during the drilling of a well is one of the most common challenges that drilling engineering faces daily. The problems in the hole represent time no productive, lost money and delay in productions plans, for this motive find a solution is important.
A technique very used for minimizing operational problems in the hole during the drilling is pump a cement plug.
What is the objective of pump a cement plug?
All cement plugs have as main objective stabilize the hydrostatic column of the mud or slurry, hydraulic isolation and provide hole integrity as well as in cases more specific the well abandonment and support for the deviation tools.
Generally, the cause principal or purposes for its use is:
- Lost Circulation Prevention
- Stuck Pipe Prevent
- Improve the well integrity.
- In the well abandonment
- During the construction of a sidetrack and
- Plug Back of a depleted zone.
Cement plug can be pumped inside of the casing as well as open hole or in the annular space between casing and open hole.
Lost Circulation Prevention: In oil fields where the zone of lost circulation is well known, pumping cement plugs generally mitigates the problem. Although the cement slurry may be lost to the thief zone, it will harden and consolidate the thief or weak formation. The cement enters the area of porous throats of the sand or microfracture, at the same time the hardening time of the cement will make it serve as plaster or insulation and minimize fluid loss.
If the lost zone it’s vey depleted is recommended use fibrous cement.
Stuck Pipe Prevention: The make a plaster in the depleted zone or area of under-pressure, the cement plug will serve as isolate and reduce the possibility of stuck pipe for pressure differential.
Improve Well Integrity: When the cement enters in pore gorges of form balanced or force and the slurry is design for give well integrity is usually reached o good integrity.
In this case is recommended use thixotropic slurry behaves like a fluid when exposed to high yield values but forms a rigid gel structure after pumping is stopped.
Well Abandonment: The cement volume and the configuration of the plug will depend of the environment regulation and laws of the country, however a abandonment plug must fulfill with the following objective:
It should prevent liquid from escaping from the injection site.
Must protect resources against flow from other zones.
Consider the diameter of the liner and the hole.
Consider the characteristics of the cement to be used.
During the construction of a sidetrack: Generally, its use density high cement with high resistance to compression to facilitate the orientation of the directional tool and its optimal functioning.
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