American Oil and Gas Reporter - February 2016 - 39

SpecialReport: Unconventional Resource Science
Recognizing the need to stay in the
productive zone while drilling the lateral,
along with the value of 3-D seismic, the
newly acquired seismic data were integrated with geosteering, using new automated time-to-depth conversion technology. In this case, seismic is converted
automatically to depth "on the fly."
In Figure 3, the first drilling segment
(green) correlates with the reference well
as shown, suggesting that we were just
below the base of the Olmos porosity.
The seismic depth profile was updated

and the planned well was adjusted accordingly. The new plan predicted that
we probably would be back in the better
porosity, along with a change in dip, at
the next segment (also green). Drilling
verified that hypothesis.
Advanced geophysical methods have
proven critical in extending the life of
the AWP Field. One of the keys lessons
Swift has learned in its experience in the
field is to use the right geophysical tool
for the task and not limit analyses to
only one technology. In this case, for in-

stance, seismic acoustic impedance is
proving a good porosity indicator, curvature and coherency are good attributes
for understanding fractures, integrated
seismic and geosteering are optimizing
wellbore design and the ability to stay in
zone while drilling horizontally, and highfrequency 3-D technology is opening
new areas of the field.
The bottom-line result of the integrated,
multidisciplinary evaluation of the Olmos
reservoir is the addition of significant
value to Swift's portfolio.
❒

Coiled Tubing Facilitates Refracturing
By Brett Fears
OKLAHOMA CITY-Low crude oil
prices are making the concept of recompleting horizontal wells effectively and
economically an intriguing topic for companies looking to increase revenue while
limiting expense. Many mature shale
wells suffering from low production still
contain large volumes of oil and gas that
can be produced through refracturing.
However, despite the considerably
lower costs required to recomplete a well
versus drilling a new one, further technological advancement in refracturing
operations is needed to allow this technique
to be an effective solution in today's industry climate.

As with hydraulic fracturing for new
wellbores, there are numerous refracturing
methods that need to be explored and investigated to make recompleting a well a
more cost-efficient and reliable strategy.
To perform a recompletion operation effectively requires isolating the initial fracture locations along the lateral, creating
additional perforations, and being able
to pump frac slurries at sufficient rates
and pressures to stimulate and prop open
new rock to produce from the new stages.
Proven fracturing processes, combined
with new technology, can be used to
achieve successful results. One approach
being investigated uses coiled tubing
technologies in conjunction with highvelocity jet perforating techniques and

FIGURE 1

This photo of a partial perforation tunnel shows the "ballooning effect" as the abrasives
return through the tunnel, which creates large surface areas inside the perforation tunnels.

chemical diverting agents to facilitate effective horizontal well recompletions.
Coiled tubing always has been a very
efficient method for conducting drilling
and workover operations, including both
perforating and hydraulic fracturing applications. CT provides an excellent balance between the speed and low cost of
wireline, and the strength and ability to
pump fluids down hole that is provided
by jointed pipe. Additionally, being able
to pump continuously without having to
break connections, and to work under
high pressure without needing a snubbing
unit, make CT a preferred method for
performing downhole operations through
highly deviated and extended-reach horizontal wells.
Jet perforation techniques use abrasive-laden fluids pumped at high velocities
to create a communication tunnel through
the steel-cased hole in the wellbore and
into the formation. The perforating tools
are carried down hole either by coiled
tubing or jointed pipe to a desired target
location, and abrasive slurry is pumped
from the surface, through the tubing and
out a specifically sized nozzle to establish
the high velocity required to penetrate
through the casing and out into the wellbore.
The abrasive perforation tunnels tend
to provide excellent flow areas with clean
and wide permeable paths, as opposed to
perforating with explosive charges, which
sometimes can leave a low-permeable
skin on the walls of the perforation tunnel
(Figure 1). These two benefits can lead
to lower pressure being required to break
down a formation during the hydraulic
fracturing process.
Additionally, with the abrasive perforating technique, perforations can be perFEBRUARY 2016 39

American Oil and Gas Reporter - February 2016

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