Hola, Natan.

Te ofrezco "lubricador", pero creo que no se trata de esto.
Lo que más me gusta para este caso es "limitador de presión".
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CIERRE PERIFÉRICO
"El **dispositivo de cierre periférico (Pack-off)** o las condiciones geológicas del agujero pueden impedir el avance del tubo...".

www.gdsinternational.com/infocentre/pdf/isaog/hwki.pdf
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Tambíén puede ser "SELLADO" o "CONJUNTO DE SELLOS":

"Cabeza compacta. Compact wellhead
Conjunto de sellos reemplazables > Retrievable pack-off".

www.motomecanica.com/cata15.htm
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OILFIELD GLOSSARY

Aquí lo describe de nuevo como "SELLADO" > SEALING ELEMENT

"PACK OFF
1. vb. [Drilling] ID: 1509

To plug the wellbore around a drillstring. This can happen for a variety of reasons, the most common being that either the drilling fluid is not properly transporting cuttings and cavings out of the annulus or portions of the wellbore wall collapse around the drillstring. When the well packs off, there is a sudden reduction or loss of the ability to circulate, and high pump pressures follow. If prompt remedial action is not successful, an expensive episode of stuck pipe can result. The term is also used in gravel packing to describe the act of placing all the sand or gravel in the annulus.

See: annulus, circulate, cuttings, stuck pipe

2. n. [Drilling] ID: 1510

A flexible, usually elastomeric SEALING ELEMENT and housing used to seal an irregular surface such as a wireline.

3. vb. [Well Completions] ID: 2751

To effect hydraulic isolation, either with a sealing device, such as a packer, or with a specialized plastic or fluid, such as a sealing compound".

www.glossary.oilfield.slb.com/ Display.cfm?Term=pack%20off
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LIMITADOR DE PRESIÓN
Otra posibilidad...

"The Model “KB” Hydraulic Set Straddle Pack-Off is a coiled-tubing or tubing-conveyed retrievable tool that PROVIDES ISOLATION
inside the casing".

AISLADOR / AISLANTE ...
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LUBRICADOR (no creo...)

"· Tubería Flexible de Diámetro Reducido:
Consiste en inyectar fluidos a través de una tubería capilar hasta la profundidad de interés requerida dentro de pozos productores
de hidrocarburos
Beneficios:
- No se requieren modificaciones en los cabezales para la instalación.
- Solo es necesario instalar un **pack off (lubricador)** para 10,000 psi, adaptado al árbol de válvulas.
- Es posible instalar el sistema en pozos fluyentes sin interrupción de la producción.
- Al incrementar la eficiencia en la inyección de productos químicos, se reducen los costos de operación y mantenimiento.
- Este sistema puede ser removido o reinstalado en otro pozo a un mínimo costo.
- No se requiere equipo de reparación".

www.are-delta.com/solutions.html
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Un cordial saludo.
:)

pack off
1. vb. [Drilling] ID: 1509

To plug the wellbore around a drillstring. This can happen for a variety of reasons, the most common being that either the drilling fluid is not properly transporting cuttings and cavings out of the annulus or portions of the wellbore wall collapse around the drillstring. When the well packs off, there is a sudden reduction or loss of the ability to circulate, and high pump pressures follow. If prompt remedial action is not successful, an expensive episode of stuck pipe can result. The term is also used in gravel packing to describe the act of placing all the sand or gravel in the annulus.