American Oil and Gas Reporter - February 2016 - 43

SpecialReport: Unconventional Resource Science
time for the diverting agents may be
recorded and correlated with the pressure
charts to possibly confirm the desired location was fractured appropriately.
Diversion Process
The second method utilizes a diversion-type fracturing process that treats
the entire wellbore, as opposed to targeting
individual stages. This greatly decreases
the time required to execute the entire
operation, and also creates less wastewater.
As with the first method, this diversion
technique can be used on both new wells
and recompletions.
All perforations are completed in a
single run using coiled tubing and an
abrasive jet perforating tool, after which
the BHA is pulled to surface, leaving an
open wellbore to carry out the fracturing
process. The initial frac treatment is
pumped first, followed by diverting agents
to isolate the stage. In many cases, the
formation can be seen breaking down
during fracturing through a fluctuation
in the treatment pressure.
As diverting agents begin to isolate
perforations, an increase in treatment
pressure indicates the frac fluid has been
diverted to other perforations. Because
of varying formation gradients, the treatment pressure may increase until a breakdown is seen on the newly exposed per-

forations. Once this occurs, the next stage
can be fractured and the process may be
repeated as needed. As in the first method,
cleaning out the diverting agents is completed once all frac treatment fluid has
been pumped.
Case History
A fracturing process using a fibrous
diverting agent was performed on a new
well in Grayson County, Tx., which borders the Oklahoma state line and is where
activity has focused on horizontal Woodford Shale development. A total of 144
abrasive perforations were made using
coiled tubing, with seven frac stages making up the entire hydraulic fracturing volume. After the perforations were made,
CT and the BHA were removed from the
wellbore to prepare for the fracture treatment.
The diverting agent was pumped down
hole after the initial frac stage. A spike
in pressure was observed after the volume
to displace the diverting agent was
pumped, indicating a successful isolation
of the fractured zone.
Acid was pumped directly behind the
diverting agent to assist in the subsequent
breakdown for the next fracture treatment.
After the final frac stage was completed,
the diverting agents were removed from
the wellbore using a downhole milling

assembly. A section of the job history is
shown in Figure 2.
Positive indications of the diverting
agents were seen during the milling operation, thus confirming a successful diversion as well as providing the operator
with data indicating where each frac stage
had been pumped. This diversion method
can be applied easily to a recompletion
simply by isolating existing perforations
prior to the initial frac stage.
Conclusion
While there are many benefits to fracturing/refracturing methods based on
coiled tubing, abrasive perforating and
diverting agent technologies, some of the
main considerations are speed, cost effectiveness and reliability. Having to run
downhole tools such as packers, plugs
and sleeve systems can be quite expensive
and complex, and may require large tool
strings, extensive drill-outs, increased
downtime, increased water requirements,
and reduced inside diameter restrictions
in the wellbore.
Being able to combine efficient and
proven technologies to achieve successful
fracturing and refracturing operations is
a very effective strategy to compete with
the economic challenges inherent in today's oil and gas operating environment.
❒

FIGURE 2
Job History Chart Showing Frac Stages 3-7 of Well
Using Fibrous Diverting Hydraulic Fracturing Method
Blender Prop Conc (ppg)
Treating Pressure (psi)

8.000

BH Prop Conc (ppg)
Slurry Flow Rate (bpm)

8.000
50.00

9,000

6.400
7,200

Diverting
Agent
Lands

6.400
40.00

4.800

5,400

30.00

3.200

3,600

20.00

1.600

1,800

10.00

0.00
0.00

0.00
0.0

72.4

144.8

217.2
Time (min)

289.6

362.0 0.00

BRETT
FEARS

Brett Fears is team leader for Thru
Tubing Solutions' engineering department, where he has been working for
six years. He has 15 years of experience
as a design engineer for downhole
tool applications. Prior to TTS, Fears
spent time designing tools for Halliburton Energy Services' casing equipment department. He graduated in
2001 with a B.S. in mechanical engineering from the University of Oklahoma, and received an M.S. in mechanical engineering from Oklahoma
State University in 2008.
FEBRUARY 2016 43

American Oil and Gas Reporter - February 2016

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