Crosswell acoustic surveying in gas sands: travel-time pattern recognition, seismic Q and channel waves
The application of crosswell acoustic measurements to gas sands research has been explored through surveys conducted in the Mesa Verde formation at the Department of Energy Multi-Well Experiment (MWX) site near Rifle, Colorado. The borehole tools used in the survey are similar in concept to those used in commercial service for sonic logging, but they are especially adapted for the stringent requirements of crosswell shooting in hot gas wells. Important information about the geologic structure between wells can be extracted from crosswell scans without resorting to elaborate processing. A useful representation is a display of the travel time of P-waves in terms of the cylindrical coordinates of the transmitter referenced to the receiver. This is known as a gamma-depth (..gamma..-Z) plot. Such a representation may yield distinctive patterns, which can be interpreted based on the successful replication of the pattern through computer simulations. The apparent seismic Q of P-waves transmitted through the sands at the MWX site is derived using two methods. The first applies to crosswell surveys in which signals can be acquired over a significant range of source-receiver distances. A Q of 15 between well pair MWX 1/2 is derived in this manner. The second method makes use of signals transmitted between wells in a three-well complex and provides an estimate of seismic Q for the rocks bounded by each well pair. Q estimates derived from this technique are 18, 30, and 28 for well bores MWX-1/2, MWX-2/3 and MWX-3/1, respectively. Channel waves propagate through the MWX coals. Evidence suggests that tube waves launched in the transmitter well give rise, under appropriate conditions, to channel waves, which in turn excite tube waves in nearby wells that penetrate the same channel. Although the sequence of conversions is weak, the resulting waveforms are coherent enough to resolve the channel waves through stacking. 8 refs., 10 figs.
- Research Organization:
- Los Alamos National Lab., NM (USA)
- DOE Contract Number:
- W-7405-ENG-36
- OSTI ID:
- 5928446
- Report Number(s):
- LA-UR-84-1140; CONF-8506104-2; ON: DE85010777
- Resource Relation:
- Conference: 26. Society of Professional Well Log Analysts annual logging symposium, Dallas, TX, USA, 17 Jun 1985
- Country of Publication:
- United States
- Language:
- English
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58 GEOSCIENCES
COLORADO
SANDSTONES
ACOUSTIC MEASUREMENTS
SEISMIC WAVES
VELOCITY
EXPERIMENTAL DATA
PATTERN RECOGNITION
SONIC LOGGING
WELL SPACING
DATA
FEDERAL REGION VIII
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NORTH AMERICA
NUMERICAL DATA
ROCKS
SEDIMENTARY ROCKS
USA
WELL LOGGING
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580203 - Geophysics- Geophysical Survey Methods- (1980-1989)