American Oil and Gas Reporter - October 2015 - 74

SpecialReport: ED&P: Eagle Ford
pressure characteristics pre- and postfrac. Heinson says he expects to see a
new curve and upward shift in production
profiles if the refracs are done right. "We
are not looking just to accelerate existing
production," he emphasizes.
Sanchez does not anticipate much in
the way of near-wellbore problems in its
collection of wells. "We have not seen
deterioration of our existing production
profiles or loss of reserves that would indicate some kind of damage mechanism
or loss of connection with the well,"
Heinson states.
Consequently, he says, the company
is not anticipating small volume refracs
in its overall completion program.
One of the biggest challenges Heinson
says he sees in the Eagle Ford is that
during new drilling, offset wells are hit by
frac fluid. "More often than not, you see a
lot of frac water being produced from all
offset wells," he describes. "We go from
producing oil and gas to producing nothing
but water for as much as 30-60 days."
Fortunately, he says, with a very few
exceptions, the wells always have come
back to the levels they were producing
before and there has been no loss of reserves. "That is an important finding for
us," Heinson avers.
The relationship between new and existing wells raises the prospect of coordinating drilling and refracturing. "We

are evaluating whether to refrac at the
same time there would be a frac hit,"
says Heinson. "At a minimum, we might
be able to avoid lost productivity, and
potentially we could add complexity or
frac geometry growth as we essentially
zipper into existing wells."
It is an intriguing concept that Sanchez
is investigating. "This could have an impact on all development planning and
our entire capital budget," Heinson reasons.
Improving On The Original
BP began refracturing horizontals in
2013 with five wells in the Woodford
Shale, then added another nine in 201314. Those wells reveal much about what
does and does not work, contends Sam
French, BP's senior reservoir engineer.
The company has carried this knowledge
forward to the Eagle Ford, where it has
conducted two refracs to date.
French says the Woodford wells were
drilled early in the industry's understanding
of how to complete horizontal shale wells,
and had stage spacing of 500 feet or
more. "We now believe that 300 feet is
closer to the optimum," he says, commenting that wells with the wider spacing
likely have significant amounts of unstimulated pay.
French says BP experimented with different diversion methods, first using rub-

F-1

900

600
300

0
Jul-12

Jan-13

Jul-13

Jan-14

Jul-14

1,200

900

600

300

Refrac Operations

D-1

Gross Gas Rate (Mscf/d)

1,200

1,500

Refrac Operations

Gross Gas Rate (Mscf/d)

1,500

ber-coated nylon balls and later switching
to biodegradable balls. Finally, he says,
BP chose a biodegradable, mixed-size polylactide acid resin agent because it achieved
higher diversion pressure increases.
In the Woodford, French says BP witnessed an average two- to threefold production increase from refracturing. Those
wells were five-six years old and had
3,000- to 5,000-foot laterals, and produced
primarily dry gas, he adds.
Meanwhile, some older Eagle Ford
completion designs may have had too
many perforation clusters for the rate
that was pumped, French suggests. "If
we had five clusters per stage, we may
have placed fractures in only three or
so," he observes.
He says shutting off the current producing stages while refracturing allows
the refrac to focus the limited energy on
bypassed pay.
French adds that BP's two Eagle Ford
pilot wells were two-three years old and
had 4,600-foot and 4,900-foot horizontal
sections. He adds that these wells had
poor production from their original completions, compared with wells with newer
completion designs. By refracturing the
initial perforations, he says BP added
significant amounts of natural gas to the
wells' expected recoveries. Production
rates in the two dry gas wells increased
sixfold, French says, while initial pro-

0
Jul-12 Oct-12 Jan-13 Apr-13 Jul-13 Oct-13 Jan-14 Apr-14 Jul-14

H-1
1,200
900
600
300

Refrac Operations

Gross Gas Rate (Mscf/d)

1,500

0
Sep-12 Dec-12 Mar-13 Jun-13 Sep-13 Dec-13 Mar-14 Jun-14

74 THE AMERICAN OIL & GAS REPORTER

Initial production and decline rates for three wells in BP's initial
five-well refracturing pilot in the Woodford Shale are shown here.
The company points out that the F-1 well was affected by an increase in gathering line backpressure after four news wells were
put on line a few days after the refracture. Once backpressure
dropped, the production rate increased again. Altogether, BP reports an average two- to threefold production increase from its
Woodford refracturing.

American Oil and Gas Reporter - October 2015

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