CASE STUDY
One-Run In Situ Stress Testing by Microfracturing
Guides Hydraulic Fracturing, Antelope Shale
MDT tester in dual-packer configuration isolates intervals for measurements
to calibrate mechanical properties from sonic logs, San Joaquin Valley
CHALLENGE
Determine the magnitude of in situ stress
for designing hydraulic fracturing of multiple
intervals in the Antelope Shale.
SOLUTION
Efficiently microfracture test multiple
intervals in a single run by deploying the
MDT* modular formation dynamics tester
to isolate the intervals between dual packers
and inject fluid to create and propagate
small-scale hydraulic fractures.
RESULTS
Successfully placed hydraulic fractures
in the Antelope Shale on the basis of
accurate in situ stress measurements
obtained by conducting multiple
microfractures with the MDT tester
in a single run.
Introducing hydraulic fracturing to the Antelope Shale
An operator in the southern San Joaquin Valley needed in situ stress measurements to design
effective completions employing hydraulic fracturing. Whereas the Monterey Formation produces
from prolific natural fractures, its equivalent in the southern San Joaquin Valley, the Antelope
Shale, is not naturally fractured. For the Antelope Shale to become a major unconventional
resource, hydraulic fracturing would be necessary to replace the role that natural fractures play
in the Monterey.
Directly measuring minimum stress magnitude in multiple intervals
The MDT modular formation dynamics tester effectively defines intervals for microfracture testing
with the high-performance inflatable elements of the Dual-Packer Module. Even thin zones can be
isolated between the packers for evaluation with small, controlled injection volumes. In a single
trip in the well, multiple intervals can be efficiently individually tested. By measuring the formation’s
pressure response immediately downhole, the MDT tester avoids the frictional loss and time lag
that compromise surface pressure measurement.
Designing effective fracture stimulation
Because fracture height is primarily controlled by the minimum in situ stress, measuring the
contrast in the closure pressure during microfacture tests is critical. The operator gained a wealth
of useful information in a single trip of the MDT tester by successfully determining the in situ stress for
multiple intervals. These discrete measurements were used to calibrate mechanical properties derived
from sonic logs for designing efficient, effective fracturing operations for the Antelope Shale.
Breakdown pressure
Fracture propagation
pressure
Fracture
propagation
pressure
Instantaneous
shut-in pressure
Pressure
Instantaneous
shut-in pressure
Reopening
pressure
Minimum in situ stress
Interval pressure
Closure
pressure
Closure
pressure
Flow rate
Hydraulic
pressure
Injection cycle 1
Injection cycle 2
Time
Repeated fluid injections create and propagate small-scale fractures in the interval isolated
between the MDT tester’s dual packers. The difference in the closure pressures is used
to determine the minimum in situ stress that controls the fracture height created during
hydraulic fracturing.
*­ Mark of Schlumberger
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Formation Evaluation