American Oil and Gas Reporter - September 2017 - 63

SpecialReport: Tubulars Technology

Long-Lateral Wells Drive CT Advances
By Victor A. Schmidt
Special Correspondent

The world of coiled tubing continues
to evolve as operators drill more extended
horizontal wells. Longer laterals mean
more CT in the hole, more drag, more
resistance to CT movement, and of course,
increased wear and stress on the pipe.
The need to overcome these challenges
is driving the industry to develop new
tools for CT work, new metallurgies to
add length and durability to the CT string,
and even new ways to construct wells.
"Most tight oil and shale gas wells
being drilled these days are not overly
complicated, but are single bores, with
more than 90 percent containing laterals.
All laterals have undulations, but most
are within 2 degrees per 100 feet of being
straight," notes Mark Spitz, coiled tubing
engineering manager of Cudd Energy
Services.
"With longer laterals, the industry
seems to be moving to less severe curvatures in the build rates, which aids in
pushing tubulars laterally. Build angles
of 10-12 degrees/100 feet used to be the
norm in horizontal shale wells. Now the
build angles are 6-8 degrees/100 feet,"
he states.
Typically, horizontal wells are engineered "toe up," with a 90-93 degree
total rise angle toward the toe, according
to Spitz. For toe-up wells, accurate modeling helps determine the reach limitations
of CT and helps operators determine how
to complete laterals beyond this reach
limit when using standard drillable frac
plugs milled out with CT after each stage
is completed. Beyond a certain measured
depth, operators can opt to use other
means of completion, whether using stick
pipe, slick frac technology or dissolvable
plugs to stage well fracturing operations,
he explains.
While conventional plug-and-perf
methods most commonly are used to initiate hydraulic fracturing treatments in
multistage horizontal wells, Spitz reports
that CT-actuated sleeve and port systems
may prove to be effective in lateral wells
with high stage counts, eliminating the
need to mill out plugs after fracturing.
This fracturing method utilizes an isolation packer, which, when positioned
and set, hydraulically opens the sleeve

assembly. Spitz notes that downtime between each frac stage can be only a
matter of minutes. Although higher cost
may be associated with using the CTinitiated sleeve and port technology in
comparison with a conventional plugand-perf system, the efficiency of the
CT unit and the speed of downhole sleeve
operations provide an effective and efficient fracturing method, he relates.
"Jointed pipe has advantages when
you need to rotate down hole or touch
something that is just out of reach for
CT. When you start dealing with pressure,
however, CT is hands down the way to
go," notes Spitz. "Most wellhead pressures
range from 2,000 to 4,000 psi in today's
typical horizontal wells, although some
are lower or higher. Considering CT's
ability to continuously circulate in an efficient manner, there is no reason not to
utilize coiled tubing when dealing with a
well with laterals of 10,000 feet or less."
For 10,000-foot and longer laterals,
25⁄8-inch CT is the next CT size to consider,
and it is becoming available more readily
across the various shale plays, Spitz
offers. He points out that it does have
limitations in "super laterals" and U.S.
Department of Transportation restrictions
hinder its ability to be accessible in all
shale plays. "It will be hard to transport
a 25⁄8-inch CT work string into the Utica
Shale in Ohio, where companies are
drilling some of these record-setting super
laterals," he comments.
This summer, Eclipse Resources drilled
the Outlaw C 11H with a 19,500-foot
lateral extension (total measured depth
of 27,750 feet), breaking the lateral length
record the company had established earlier
this year on the 19,300-foot Great Scott
3H (27,400 feet MD) and on the 18,544foot Purple Hayes (27,048 feet MD) in
2016. All three wells were drilled in the
liquids-rich portion of the Utica play in
Guernsey County, Oh.
State Of Recovery
Jeff Seal, U.S. CT technical manager
for C&J Energy Services, characterizes
conditions in the coiled tubing well services market as "steadily improving," but
he says technical and business challenges
remain. "With improved rig counts, the
CT industry is in a recovery state," Seal
assesses. "While it has been difficult the

past couple years to make major equipment
upgrades, we are starting to see some of
that take place."
According to Seal, one area where
upgrades definitely are occurring is an
improved string manufacturing process.
Now, coiled tubing string manufacturers
are making tempered and quenched CT
strings, he says. "The tempering and
quenching process normalizes the steel
and bias welds' molecular structure," he
says, adding that tempering and quenching
creates strings with higher tensile strength,
less fatigue and longer life, fewer problems
with microbial induced corrosion, and
possibly more extended-reach capabilities
as a result of the greater-strength steel.
"The new CT materials are harder,
more durable and better able to withstand
repeated running and bending cycles for
longer service life," he remarks.
In addition to replacing worn service
strings with higher-performance CT, the
longer laterals being drilled in resource
plays require larger-diameter CT to get
the work done. "We are adding two 25⁄8inch units to our fleet with very large
reels that hold 25,000 feet of coiled tubing
on longer trailers," Seal says.
Extra axle sets are used on the trailers
that haul the large reels to spread the
weight and stay within weight and axle
load limitations for over-the-road transport.
Narrow lease roads also can be problematic
for making turns with the extended-length
trailers, requiring sufficiently wide turns
to be built into lease roads for the well
servicing equipment, he adds.
One of the most difficult challenges
facing the CT services sector is finding
qualified personnel to operate the equipment, Seal reports. "You have to have
the people to man the CT units," he
offers. "C&J Energy Services operates a
driving school to help new hires get their
commercial driver's licenses and operate
trucks and equipment as safely as possible,
but finding the right people to hire can
be tough."
Getting To TD
Getting CT to total depth to stimulate
wells or drill out plugs after fracturing is
made more challenging as operators extend
lateral lengths, according to Steven Isaacks,
coiled tubing product line director at National Oilwell Varco. The company has
SEPTEMBER 2017 63
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