American Oil and Gas Reporter - February 2015 - 63

SpecialReport: Unconventional Resource Science

Permian Well Shows Benefits Of CTFS
By David Luna,
Ruslan Filyukov
And Otman A. Algadi
FORT WORTH-The Permian Basin
is experiencing a significant increase in
oil-directed horizontal drilling. In fact,
according to the U.S Energy Information
Administration, the Permian has far and
away been the fastest growing region for
horizontal oil drilling activity over the
past two years, as operators target the
Wolfcamp, Bone Spring and other unconventional oil formations in West Texas
and Southeast New Mexico with horizontal
well trajectories.
At the same time, hydraulic fracturing
technology continues to evolve rapidly,
with new technologies focusing primarily
on making the process more efficient,
cost effective and environmentally friendly.
One example is coiled tubing-activated
frac sleeves (CTFS), a cost-effective and
efficient multistage fracture stimu lation/completion system.
Although a relatively new technology,
CTFS has been used extensively in Canada. Building on the experience gained
with this patented technology in Canadian
operations, CTFS was used to successfully
stimulate a 29-stage Bone Spring horizontal well operated by XTO Energy Inc.
in Lea County, N.M.
CTFS effectively reduces the required
hydraulic horsepower, fluid usage, and
downtime between frac stages. It is compatible with open-hole or cemented completions and provides full wellbore access
without milling for unobstructed production. Bottom-hole temperatures and pressures are recorded using memory gauges
attached to a CT-deployed bottom-hole
assembly for post-treatment analysis and
diagnostics. The system provides rapid
recovery from screen-outs, minimizing
downtime and adding flexibility to treatment design.
As opposed to plug-and-perf multistage
fracturing, which is the predominant technique in the Permian, CTFS utilizes frac
sleeves that are opened hydraulically
using a CT BHA. This saves significant
amounts of time between stages, reduces
fluid consumption, and eliminates the
need to mill out plugs to initiate production. The single frac fluid entry point allows tighter spacing of frac stages and
ensures that the fracture is created at the

sleeve.
As demonstrated in the Bone Spring
horizontal well application, CTFS multistage fracturing is a fast, effective and
efficient stimulation technique. It efficiently
minimized nonproductive time, considerably reduced fluid consumption, and
shortened post-frac clean-out time. All
29 frac stages were completed safely and
in a timely manner, and the system ensured
that fractures were created at the ports to
provide effective stimulation throughout
the entire lateral section.
CTFS does not involve wireline to
perforate casing and initiate contact with
the formation, or require dropping balls
to open ports or set composite plugs to
isolate each stage. Instead, it includes
frac sleeves that are pressure balanced
and hydraulically opened using a specially
designed BHA deployed on CT, providing
an unlimited number of frac stages. The
sleeves are run with casing and cemented
in place or attached on a liner with
external packers for open-hole completions. The CT BHA is run down hole
prior to starting the fracturing process.
Plug-and-perf techniques treat multiple
clusters at once, which can result in uncontrollable fractures and poor overall
stimulation efficiency of the entire lateral
section. In contrast, CTFS is a targeted
fracturing technology that improves reservoir drainage in horizontal wells by ensuring the fracture is initiated at the
sleeve. It also leads to better production
performance compared with other com-

pletion and stimulation techniques by increasing the number of frac stages with
tighter spacing in between.
System Design
The two main parts of the CTFS
system are the hydraulically activated
frac sleeves and the CT BHA (consisting
of a mechanical casing collar locator,
packer, sand jet perforator, and pressure
and temperature memory gauges for this
operation). The CT BHA provides realtime monitoring capabilities of bottomhole fracturing pressure using the CT
dead string to provide more reliable data
to optimize treatment on the fly.
The casing collar locator is used to
accurately locate the frac sleeves and
place the BHA in the proper location.
The packer is used to open the frac sleeves
and provide isolation from previous frac
stages.
The sand jet perforator allows a frac
stage to be created where a sleeve was not
installed or where an extra stage is desired.
It is also used as a circulation sub to
enable fluids to be circulated through the
CT to surface in case of a screen-out. The
pressure and temperature memory gauges
attached on top of the packer measure
bottom-hole flowing pressure and temperature, as well as pressure and temperature
under the packer to identify communication
between stages (Figure 1).
The CT-activated frac sleeves are pressure balanced and are opened by creating
a pressure differential across the sleeve.

FIGURE 1
Coiled Tubing Bottom-Hole Assembly
Upper memory pressure & temperature gauges

Sand jet perforator

Coiled tubing

Packer

Spacer tube

Casing collar locator

Lower memory pressure &
temperature gauges

FEBRUARY 2015 63

American Oil and Gas Reporter - February 2015

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