Surge reduction reduces excessive surge pressure experienced when
‘conventionally’ running close tolerance liners or sub-sea casing strings. A surge
reduction system reduces the surge pressure that would otherwise break down
the last casing shoe or a section of the open hole. It also reduces surge pressure
by minimizing the returns that normally are pushed up the small annulus of the
liner/casing or the liner/hole. The majority of the displacement volume flows up
the inside of the liner/casing and crosses over to the drill pipe/casing annulus
above the liner or sub-sea running tool. This redirected flow is made possible by
the use of a "diverter" sub and is facilitated by use of auto-fill float equipment.
The system addresses a major industry concern: running liner hanger equipment
with drilling fluid containing large amounts of cuttings and debris. By changing
the flow path of the drilling fluid up through that equipment with the largest
opening float equipment available today, the system minimizes that effect. The
system is able to handle large amounts of cuttings and wellbore debris routinely
encountered during drilling operations.
Surge reduction tools are designed to run with any mechanical or hydraulic set
liner hanger or sub-sea running tool. In addition, tandem sets of the diverter sub
can be run with large diameter sub-sea casing strings that are using a drillpipe
stinger for cementing purposes. Operators also are using the diverter subs
for reducing surge while running tie-backs instead of using bleeder caps, thus
reducing rig time having to manage fluid over-flow.