1. Integrated well-log, VSP, and surface seismic analysis of near-surface glacial sediments:
Red Lodge, Montana
J.Q. Huang, Department of Earth and Atmospheric Sciences, University of Houston.
J. Wong, CREWES, University of Calgary.
Summary Data acquisition and avaiable well logs 2D/3D seismic analysis Hydrophone VSP tube wavefield processing Wireline logs, 2D seismic, and VSP comparison
The UH 2010 Montana field camp conducted a series of The GB-1 well locates at 450 07’48.318” N, 1090 16’48.798” W, with 2D seismic profile was 5.2m south offset hydrophone Figure 8: Hydrophone Three events can be identified on the L-plot. 40m depth event,
geophysical surveys and had the goal of determining the the elevation of 1881m, has water level at 15m and the metal casing acquired near the well GB-1, Figure 5: Upper: 2D seismic tube wavefield was chosen for
VSP with primary
shows on geophone Z component stack. Also gamma ray log
downgoing P wave
thicknesses of glacial benches formed from glacial outwash from down to 13m, the logs can be interpreted from this depth. The well is it has 72 receivers at 5m survey fold analysis. The
tube wavefield processing. picks (green). increases, velocity decrease at 40m depth (Fig. 12).
background color shows the
the Beartooth Mountains. lined with cement casing. From driller’s log, it encounters about 13m spacing and shots (vibroseis fold coverage in the survey. The tube wave velocity
Interval velocity
50m depth event shows on geophone Z component stack, and
calculated from the
The well logs included measurements of conductivity, radioactivity of unconsolidated overburden, this gravel may be the youngest truck) at 5m spacing (N50E). Bottom: 3D seismic survey fold
changes at 90m depth caused first arrival times. hydrophone tube wavefield stack. Also conductivity increases,
analysis. 8 receiver lines
(gamma ray), temperature, and sonic velocity. The multi-offset VSP pulse of glacial deposits. The gamma ray, conductivity, resistivity The signal length recorded shown by blue dots (N50E) and by the wave engergy trapped velocity decreases at 50m depth. The driller’s report shows a
was undertaken using surface sources (an accelerated weight drop indicate a boundary at 25m. The full wave sonic log is increased was 600ms with 0.125ms 10 shot lines (N40W) shown by
at the perforation zone at this water perforation zones at 50m depth as well.
pink dots.
and sledge hammer) with a hydrophone string and a downhole, from 1500m/s to 2500m/s at 25m depth as well (Fig. 2). sample rate (Fig. 5). The depth (Fig. 8). To get wavefield 65m depth event shows on geophone Z component stack. Also
wall-clamping, 3-component geophone. Sonic and VSP velocities The wall-clamping 3C geophone near surface P wave separation, a 17-point median gamma ray log increases, velocity increases at 65m depth.
Figure 6: Upper: Typical
ranged from 1500m/s in the very near surface to 3000m/s at 85m was placed at depths ranging refraction velocity model shot record from the 2D filter was applied to separate The VSP velocities shows a velocity change at 25m depth, same
depth. A distinct black clay layer (with high conductivity, high from 4m to 114m with half-meter shows a layer at 25m depth seismic survey. Head
the wavefield. A deconvolution fashion changes are also detected from geophysical logs, which is
wave first break picks
gamma ray, and low velocity) was penetrated at 85m. High- intervals. A hydrophone string (Fig. 6). indicate in blue lines. with 100ms operation window interpreted as the total glacial deposits in this study.
resolution 2D and 3D seismic surveys were designed and acquired covered the depths from 6m to 3D seismic survey has 152 Bottom: Near surface P
produces sharper and better-
wave refraction velocity
near the well GB-1. On the L-plot composite displaying well log 112m with half-meter intervals. receivers per line at 2m model with weathering defined reflection events. A
data, and the VSPs corridor stack, three reliable reflections The variable VSP were acquired spacing and 9 shots (10lb layer velocity 800m/s
outside 100ms corridor stack to
Figure 2: Geophysical logs from the GB-1 replaced by glacial deposit
were analyzed, and 50m depth one also shows on driller’s report as by different combination of well as acquired in 2010. Different geophysical sledgehammer) per line at velocity 1800m/s. get the final reflection series Figure 9: Displayed with Ormsby filter (20-40-150-300
a water perforation zone. The VSPs velocities and sonic log show a source and receiver (Fig. 3). logs have the same fashion of change at the 6m spacing. The signal (Fig. 9). Hz) and AGC (500ms window length).
same depths, which are highlighted by red lines.
velocity increase at 25m depth, which is interpreted as the total From the source type, the sledge length recorded was 1024ms Upper: Wave field separation. Middle: Deconvolution.
Bottom: Corridor stack.
glacial deposits in this study. hammer source VSP has weaker with 1ms sample rate.
signal and lower signal-to-noise Near-offset geophone VSP processing Figure 12: L-plot of VSP (TWT),
Geology and motivation Hydrophone VSP tube wavefield separation sonic & gamma logs, and VSPs
ratio. From the receiver type, the corridor stack.
The study area, near Red Lodge hydrophone shows a strong The 3m east offset geophone/AWD VSP with half-meter receiver
effect from tube waves, which is There are 13 different offsets from 3.2m-27.2m (2m interval) in the interval and 0.5ms sampling rate was processed. The vertical Z
Montana, is close to the border
the wave that travels through the south walk-away VSPs (Fig. 3). The hydrophone VSP shows component was chosen to be processed because consistency of
of Montana and Wyoming.
water along the GB-1 water well. Figure 3: Base map of the GB-1 well VSP strong effects from tube waves, and the tube wave has water upgoing P wave events. A 21-point median filter for field References
During the last glacial maximum
The wall-clamping geophone surveys. The symbol indicates different velocity around 1500m/s which is similar with glacial deposit separation. A deconvolution with 30ms operation window produces
(approximately 12,000 to 20,000
shows more constant signal combination ofupper right corner. refer to the
source and receiver, velocity (1800m/s). sharper and better-defined reflection events. A 21-point median Huang, J.Q. and J. Wong, 2011, Integrated well-log, VSP, and
years ago, locally called the legend on the
without the effect from tube Median filters have been applied to remove the downgoing and filter was then applied to the deconvolved upgoing reflection events surface seismic analysis of near-surface glacial sediments: Red
Pinedale), mountain glaciers
waves. upgoing tube waves from 5.2m south offset hydrophone VSP. First to flatten and enhance the deconvolved upgoing wavefield. 50ms Lodge, Montana: SAGEEP, 24, 227-227.
formed in the Montana area,
break picked on primary downgoing tube wave, aligned on 300ms windowed edge corridior stack was applied to get final stack (Fig. Hinds, R.C., N.L., Anderson, and R.D., Kuzmiski, 1996, VSP
picking up and transporting rock Theory refraction critical offset calculation to be subtracted by the median filter. The first breaks were picked 10, Fig. 11). interpretive processing theory and practice: Soc. Explor. Geophys.
fragments. In our case, the
manually for better accuracy and then interpolated to make sure Ritter, D.F., 1964, Terrace development along the front of the
glacial deposits were formed by A four layer forward geologic model
every trace has a first break time value in the header. Then first Beartooth mountains, southern Montana: Ph.D. thesis, Princeton
rivers and streams running from was built for understanding local
break picked on primary upgoing tube wave, aligned on 300ms to University.
the glacier onto the plains. geology (Fig. 4). The P wave
be subtracted by the median filter. Stewart, R.R., 1984, VSP interval velocities from traveltime
Nearby outcrops show the velocity was picked from the sonic
The comparison of before and after removing the tube waves is inversion: Geophysical Prospecting, 32, 608-628.
glacial till deposits of rock size log, the S wave velocity was
calculated using G. Nottis’ equation shown in Figure 7.
ranging from 0.3m to 3m in
diameter (Fig.1). The total (Nottis, 2010), Acknowledgements
thickness of glacial bench is Figure 7: Hydrophone gather before and
Figure 10: First breaks picks (green lines) from the 3m
east offset geophone vertical component gather,
around 23m (Ritter, 1964). Where D is depth in ft, and Vs is in after removing the tube waefield, displayed displayed with Ormsby filter (30-60-150-300 Hz) and We express our appreciation to the Allied Geophysical Laboratory at
ft/s. with Ormsby filter (20-40-150-300 Hz) and AGC (500ms window length). And comparison of the University of Houston for supporting this work. We also thank
Figure 1: Upper: General location map of Red Lodge, Montana, the AGC (500ms window length). The primary sonic log and VSPs interval velocity from the GB-1
location of study site is annotated with a red arrow. Density was calculated using downgoing and upgoing tube wave are well. GEDCO for use of their software.
Middle: Plane view of the field site, the glacial movement direction Uyanik’s equation (Uyanik, 2010), illuminated by arrows.
Figure 11: Displayed with Ormsby filter (30- The 2D and 3D surface seismic designs were generated using
shows in red arrow. Figure 4: 2D seismic refraction critical offset 60-150-300 Hz) and AGC (500ms window OMNI seismic survey design package. The VSP was analyzed by
calculation using Snell’s law, the offset was length).
Bottom: The field site of the glacial bench outcrops near the GB-1 well Where ñ is KN/m3 used in refraction first break picking for Upper: Wave field separation. Middle: using VISTA VSP package by GEDCO.
(Pers. Comm. R. Stewart, 2011). (kg/m3=100KN/m3), and Vp is in m/s. refraction static analysis. Deconvolution. Bottom: Corridor stack.
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