tesco casing drilling - OilProduction.net

Reducing Non-Productive Time
Variations in the straightness of casing smear drill cuttings, sealing pores in formations in what is known as the Plastering Eff e c t .
PLASTERING
Casing coupling is forced against
the bore wall as it advances into the
borehole.
As mud is smeared into the formation,
filter cake builds up on the borehole
wall.
Filter cake and cuttings are plastered
against the borehole wall by the
coupling, sealing porous formations .
An added benefit of the CASING DRILLING process is the Plastering Effect,
or smearing, caused by continuous trowelling of the wellbore wall by the
casing. Filter cake is smeared into the wall and is not scraped off by bit
passage or tool joint impacts. Cuttings are ground up more finely.
Generally, fewer cuttings return to the surface; instead they are smeared
into the wall, further strengthening the wellbore which offers the additional
benefit of improved well control and stability.
Circulation losses are reduced even with higher Equivalent Circulating
Densities (ECD). As demonstrated by the CASING DRILLING process, smearing
has a particularly good effect when drilling through medium- and highdensity
rock. The Plastering Effect coupled with industry best practices leads
to curing lost circulation and enables continuous drilling.
Of all the benefits associated with CASING DRILLING – cost savings,
safety, efficiency – one of the primary benefits is this: In many cases, you
can save at least one trip even in zones where lost circulation persists. That
key benefit alone gives operators a case to consider CASING DRILLING.
CASING DRILLING reduces incremental costs. Many drilling engineers
plan and budget their drilling operations to account for all activities –
positive and negative. If a particular field typically encounters trouble
zones, the drilling engineer will plan and budget for those trouble zones
accordingly. Preventing and recovering from trouble is often anticipated
so as not to show up as an unscheduled event, but as a routine drilling
operation. The routine can add ever-increasing incremental costs to
operators, especially those who are trying to tap even more difficult
reservoirs.
Sometimes routine operations are activities, or costs, that could
be eliminated with a different drilling system.
Lost circulation and well control incidents are almost completely
eliminated in wells drilled using CASING DRILLING. Wells that
encounter a weak zone before or after a high-pressure zone while
drilling with drillpipe often find it difficult to balance the lost
circulation potential in the in the upper zone with well influxes in
the lower zone, particularly when tripping out of the hole with
drill pipe. TESCO encourages operators to drill ahead through lost
circulation when CASING DRILLING. Just as one might plan for a
short trip or a conditioning trip as a “prudent” practice, a certain
amount of time might be budgeted to deal with problems relating to
lost circulation in environments where it is likely to occur. Identifying
these hidden costs can make CASING DRILLING even more attractive
and drilling budgets extend further.
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