G. Waters, H. Ramakrishnan, J. Daniels, and D. Bentley, Schlumberger, and J.
Belhadi, and D. Sparkman, Devon Energy
It is now well documented that hydraulically fractured horizontal wells are
effective at stimulating shale reservoirs. Most commercial shale wells utilize
cement or open hole packers to achieve some form of annular isolation. With
annular isolation now commonly accepted, the general evolution of these
completions has been to stimulate ever shorter sections of the lateral with
multiple perforation clusters placed closely together. The objective being to
create closely spaced fractures, thereby increasing the reservoir contact area
that more effectively imposes a pressure drawdown within the ultra-low
permeability reservoir, resulting in a higher recovery factor.
The heterogeneous nature of unconventional shale reservoirs makes achieving a
complex, closely spaced fracture network problematic. Frequently, geologic
structure impacts the created fracture network to such a degree that fluid
entry points into the reservoir are of secondary importance. Horizontal well
evaluation can be utilized to optimize perforation placement and fracture
staging for near-wellbore fracture geometry generation. This has proven to
improve well performance. An additional productivity step can be achieved if
the far field fracture geometry can be influenced by techniques other than
perforation and fracture staging, especially if this technique can be applied
in real time during the stimulation treatment.
One method that has been successful at altering the created hydraulic fracture
geometry is real time microseismic fracture mapping coupled with fracture
diversion packages incorporated into the fracturing treatment. Evaluating
microseismic events in real time allows one to determine the need to change the
fracture geometry being generated. The introduction of diversion packages to
achieve this fracture geometry alteration can immediately be evaluated for
effectiveness via the microseismic activity. This feedback allows the
completions engineer to appropriately use these diversion packages so that
effective stimulation along the whole lateral can be achieved.
Examples of the use of real time microseismic fracture mapping and fracture
diversion packages are shown from the Ft. Worth Basin Barnett Shale formation.
Both initial well completions and recompletions are shown. The importance of
integrating well, geologic, log, and seismic information, is emphasized so that
decisions can be made effectively in real time using the microseismic activity
from the treatments. These examples demonstrate that hydraulic fracture
geometries can be influenced by the introduction of these diversion packages.
Resulting well productivity and fracture pressure responses validate the
effectiveness of this real time diversion and evaluation process.