American Oil and Gas Reporter - November 2015 - 53

SpecialReport: Oil & Gas Computing
Figure 1C shows a resulting 3-D opening angle/azimuth gather computed from
the 5-D gather by integrating over the
directivity angles. Figure 1D shows a 3D directional gather computed from the
5-D gather by integrating over the opening
angles and azimuths. Note the concentration of energy at low dip angles in
Figure 1D associated with the generally
flat (zero dip) reflectors in this play.
Figure 2 shows the same section after
specularity enhancement in the 5-D do-

main. Note the removal of systematic
noise and of obvious diffractions. The
image is much cleaner and more easily
picked. The gathers also are much cleaner,
providing more stable and reliable moveout estimation and analysis results of
variations in seismic velocities and amplitudes with shot-receiver azimuth and
incident angle.
Diffraction imaging allows local subsurface heterogeneities to be detected
using the diffraction enhancement pro-

FIGURE 4
Eagle Ford Depth Slices with Enhanced Primary Reflections (Top)
And Secondary Reflections from Muting Primary Reflections (Bottom)

cedure. Figure 3 shows confirmation of
this. The first set of images at the top of
Figure 3 shows different depth slices of
specularly enhanced images. A smooth
variation of the wave field is visible with
small "disturbances," the form of which
cannot be determined using only reflection
waves.
Diffraction energy is enhanced in the
set of images at the bottom of Figure 3,
resulting in slices that reveal a very different picture from that shown by the reflected field. A strong faulting plan is
seen clearly and can be interpreted easily.
Thus, significant additional geological
detail has become evident by enhancing
the diffraction energy.
A further example of the utility of
this approach is illustrated in the Eagle
Ford Shale depth slices in Figure 4, where
the separation of competing specular
events is shown. The primary specular
events in the directional gathers have
been muted, allowing the secondary reflections from the faults to become clearly
visible.
In the top image in Figure 4, a depth
slice of the specular enhanced image is
shown at 17,880 feet. In the bottom
image, the primary specular mute is applied. The dominant seismic energy from
the near horizontal horizons is muted,
leaving the weaker seismic energy from
the fault. Thus, the major faults are delineated clearly in the muted image, allowing easy picking. The stacking masks
this coherent event, leaving the interpreter
to attempt extraction in the post-stack
domain under adverse conditions.
The new approach considers migrations
as a general mapping procedure from the
surface acquisition domain to that of the
physically derived subsurface domain.

EQT Completes Gas Well
In Pennsylvania's Utica

PITTSBURGH-EQT Corporation has
completed flowback operations on its
Scotts Run dry-gas Utica well in Greene
County, Pa., achieving a 24-hour deliverability test of 72.9 million cubic feet
with an average flowing wellhead pressure of 8,641 psi.
Following the 24-hour deliverability
test, EQT reports the well produced an
average of 27.0 MMcf/d over seven days
under a restricted choke with an average
flowing pressure of 9,563 psi.
EQT adds that it planned to produce
the well at a restricted rate of 25 MMcf30 MMcf a day.
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NOVEMBER 2015 53

American Oil and Gas Reporter - November 2015

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