Using seismic crosswell surveys to determine the aperture of partially water-saturated fractures

Journal Article · Fri Jan 01 04:00:00 EST 1999 · Geophysics

DOI:https://doi.org/10.1190/1.1444511· OSTI ID:329235

Kaelin, B; Johnson, L R ^[1]

---

1. Lawrence Berkeley National Lab., CA (United States)

An air injection experiment in a shallow fractured limestone at Conoco`s borehole test facility near Newkirk, Oklahoma, has shown large effects on the amplitude but small effects on the traveltime of the transmitted seismic waves. The authors have analyzed data from a seismic monitor survey in the kilohertz range performed during the experiment and have modeled the fracture zone as a single fracture. The large amplitude decrease during the experiment is mainly attributable to the impedance contrast between the small velocities of gas-water mixtures inside the fracture and the formation. The intrinsic attenuation of the fracture fluid seems to be a second-order effect for small apertures. During the experiment the seismic wavelengths inside the fracture become comparable to the aperture dimension, which allows an estimation of fracture apertures. The authors also have analyzed a crosswell survey acquired shortly after the experiment and computed aperture and gas concentration profiles. Aperture estimates range from <1 mm to a few millimeters, which is comparable to previous tracer tests. The results of this study are generally consistent with prior hydrologic work and single-well surveys. This study demonstrates that crosswell surveys could be an effective tool for obtaining in situ estimates of fracture aperture and gas concentration.

• Sponsoring Organization: USDOE Assistant Secretary for Fossil Energy, Washington, DC (United States)
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 329235
• Journal Information: Geophysics, Journal Name: Geophysics Journal Issue: 1 Vol. 64; ISSN GPYSA7; ISSN 0016-8033
• Country of Publication: United States
• Language: English

Related Subjects

03 NATURAL GAS
GAS SATURATION
GEOLOGIC FRACTURES
OKLAHOMA
SEISMIC DETECTION
SEISMIC SURVEYS
TEST FACILITIES
WATER SATURATION