The Amazing Benefits of Cementing Plugs

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The Amazing Benefits of Cementing Plugs
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After the casing is run into the well, a
cementing head is hooked to the top of the
wellhead to receive the slurries from the pumps.
Plugs are used during cementing operations to
help remove dispersed mud and mud sheath from the
casing inner diameter and minimize the
contamination of cement.
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There are two wiper plugs, i.e. bottom plug and
top plug also known as cementing plugs. The
bottom of the plug is pumped ahead of the cement
slurry and behind the spacer who wipes any
remaining dispersed mud from the inner diameter
of the casing as it moves down the string.
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The mud inside the casing is important to be
removed because it prevents mixing the drilling
fluids with the cement slurries. When the bottom
plug seats at the float collar, differential
pressure ruptures a diaphragm on the plug,
allowing cement to flow through, turn the corner
at the bottom of the hole or toe end of a
horizontal well. It fills the annular space
between the casing and the formation.
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Top and bottom plugs said as Cementing Plugs are
always different colors. The color for bottom
plugs and top plugs differs from company to
company though. Once the full volume of cement
has been pumped, a top plug is dropped and pumped
behind the slurry from the inner diameter of the
casing and then seats at the float collar.
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It helps in resting on the bottom plug and
causing a pressure increase at the surface
indicating that the cement has been displaced.
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Trouble with Cementing Plugs

• If you find out that wiper plugs from different
  companies have different diaphragm burst ratings,
  it can be a trouble. Plugs being exposed to the
  sun and harsh weather conditions are surely a
  sign of poor quality which leads to a
  deteriorated and cracked rubber. Burst ratings
  for the plugs the operator was using ranged from
  150 to 250 psi.

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In some cases where heavyweight pipe was used,
the diaphragms burst prematurely if not wiped the
casing properly to the float shoe. In such cases,
the bottom plug of Cementing Plugs were left
somewhere up the casing until the top plug
arrived and pushed it down. Now, when the
remainder of the casing is wiped and the mud from
the walls accumulated in the shoe joint or around
the casing shoe area and everything gets settled.
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The pressure on the cement being pumped into the
well increases until a diaphragm is broken within
the bottom plug. It permits the slurry to flow
through it and up the outside of the casing
string. After the process of bottom plug, the top
plug reaches the bottom plug, the pumps are
turned off and the cement is allowed to set.
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The time taken for the cement to harden is called
thickening time. The thickening time is also
counted for the setting wells at deep depths,
under high temperature or pressure in corrosive
environments and special cements are employed.
Both the Cementing Plugs work with the right
amount of co-ordination thus, the quality matters
a lot.
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Puyang Zhongshi Group Co.,Ltd. Address
Mazhuangqiao,Puyang City,Henan Province,China Tel
0086-371-87096210 0086-371-87096211 Fax
0086-371-87096212 Email sale_at_chinajixie.com
Website http//www.zs-oilfieldequip.com/products/
Cementing20Plugs/