American Oil and Gas Reporter - February 2021 - 75

pages 75-79_Layout 1 2/16/2021 12:01 PM Page 75

SpecialReport: Permian Resource Solutions

Smart Tracers Yield Stage-Level Insights

Frac Hit Variances
Historic overcrowding is emblematic
of today's unconventional plays, as operators continually tighten interwell spacing
to wring more production from their
leaseholds. As spacing between both vertical and lateral wells narrows from 1,500
to as low as 500 feet, operators are rightly
concerned that a child well could directly
intersect the fracture network of an older
parent or offset well. In that scenario, the
two wells will overrun each other and
share the same drainage space, with the
then-depleted reservoir pressure drawing
down production from both wells.

However, that represents the extreme;
the key is to precisely identify and characterize the type and severity of a detected
interwell communication event to determine what measures should be taken
in response to optimize well spacing
designs. Figure 1 illustrates how the
various types of frac hits impact production rates and EURs.
A direct frac hit occurs when two
proppant-filled hydraulic fractures communicate, generating tremendous pressure
spikes within minutes. Although infrequent compared with other interwell
communication events, direct frac hits,
nonetheless, are culpable for a reported
40% reduction in average child well production, while the reported effects of a
direct frac hit costs $2.5 million per well
on average at minimum.
The most common interwell communication incident on a multiwell pad is
pure fluid migrating through the discreet
fracture network (DFN) and flowing into
an area opened during frac pumping.
Fluid migration is characterized by only
medium overall pressure increases and
the pressure gradient also builds slowly
over a matter of hours. Fluid migration

FIGURE 1
Production and EUR Impacts from Various Types of Frac Hits

Completion fluid

Proppant

Proppant

Well 2

Well 1

Completion fluid

No Frac Hits, Well Spacing is Too Wide

Completion fluid

Completion fluid

Proppant

Proppant

Well 2

Well 1

Limited Fluid Migration, Well Spacing is Manageable

Proppant

Well 2

HOUSTON-As shale operators resume
infill development amid ever-tightening
well spacing and improving but sometimes
nebulous economics, frac hit issues are
re-emerging in asset development strategies. However, as affordable stage-level
flow mapping data from nanoparticlebased tracers clearly demonstrate, not all
frac hits are alike, and some types of interwell communication are tolerable in
promoting maximum reservoir drainage.
While industry statistics indicate
frac-to-frac communication is responsible for upward of $21 billion in lost
production revenue and mitigation expenses over the past two years alone,
direct frac hits account for only 12%
of detected events. By contrast, an estimated 82% of frac hit signal characteristics are, in fact, fluid migration between the existing tier-one parent well
and the newly drilled child well. Fluid
migration not only has a minimal and
short-lived effect on production, but
without it, an inordinate area between
the wells will be left unstimulated, leaving potentially significant reserves
stranded. The key is to put detected interwell flow communication events in
the proper perspective.
To detect a frac hit, infill development
projects may include chemical tracers,
offset well pressure gauges, and microseismic or fiber-optic measurements. If a
severe frac hit is detected, hasty reactive
measures, such as pumping far-field diverters, usually follow. These and other
traditional approaches to seal off detected
interwell communications not only significantly increase costs, but can be ineffectual and even harmful to production
and estimated ultimate recovery rates.
Alternatively, the efforts to promote
maximum production efficiency in unconventional wells should be abandoned
in favor of a more surgical and stagespecific approach that relies on interwell
flow mapping and stage-by-stage flow
profiles to precisely define the proximal
characteristics and types of a frac hit.
Until now, however, stage-level flow mapping was economically out of reach,
except for the roughly 1% of so-called
" science " wells.

The development of unique particlebased smart tracers and data-driven diagnostics has narrowed the economic
chasm, making stage-level flow data accessible for standard unconventional
wells. Field data confirm the capacity of
the smart tracers to consistently deliver
near real-time detection with high accuracy beyond the capabilities of chemical
tracers. Importantly, the technology does
so at a fraction of the costs in relation to
the total cost of completions and competing alternatives.

Well 1

By Talgat Shokanov,
John Oliver
and Adilkhan K. Shokanov

Proppant

Direct Prop Frac-to-Frac Hits, Well Spacing is Too Close

FEBRUARY 2021 75
American Oil and Gas Reporter - February 2021

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