Page 171 - Well Control for Completions and Interventions

Well Control Surface Equipment 163

It is possible to change the seal element with pipe in the hole. To
change the seal element under live well conditions, the pipe rams (or
VBR) below the annular preventer must be closed, locked, and integrity
tested. To conform with a two-barrier policy, two pipe rams would have
to be available. With the well secure, the top of the annular preventer can
be removed and the worn rubber sealing element extracted. The element
must be cut to enable it to be removed from around the pipe. The new
rubber sealing element is cut (never sawed) between the metal ribs and
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the new element is installed in a reversal of the removal sequence.

4.8 RAM PREVENTERS
Ram preventers are used to shut-in the well in the event of a kick,
and are used in addition to, or instead of, the annular preventer. They
can be equipped with several different types of ram block, each one per-
forming a different function. These are:
• Pipe rams: Seal around a specific size of production tubing or drill
pipe. Most rams are designed for a single string of pipe, but dual or
offset rams are available for dual string completions.
• VBRs: Designed to seal around a range of pipe sizes.
• Shear rams: To cut tubing and drill pipe.
• Blind rams: To seal the wellbore when there is no pipe across the
BOP, i.e., no pipe in the well, or after the shear ram has been used to
cut and drop the string.
• SBRs: Combine the cutting action of the shear ram and the sealing
action of the blind ram.
• Production rams: To seal around rod pump sucker rods.
Although ram preventers are designed to only hold pressure from
below, most can hold a small differential from above. Shorter in profile
(height) than annular preventers, they are sometimes the only preventers
installed where space is limited (Fig. 4.16).
Early ram preventers were manually operated. Rotation of the
threaded stem moved the ram blocks back and forth between the open
and closed position. It soon became apparent that a faster method of
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It is not possible to cut Cameron sealing elements as described above. There is also a
documented case of a Shaffer element coming out of the annular body after being split.