HR: 0800h
AN: NS31B-0395    [Abstracts]
TI: The applicability and limitation of aperture size estimation from acoustic televiewer using 3 inches physical borehole model
AU: * Hwang, S
EM: hwangse@kigam.re.kr
AF: Seho Hwang, 92, Gwahak-lo, Yuseong-gu, Daejeon, 305-350, Korea, Republic of
AU: Shin, J
EM: Jehyun@kigam.re.kr
AU: Oh, H
EM: ohayoun@yahoo.co.kr
AF: Seho Hwang, 92, Gwahak-lo, Yuseong-gu, Daejeon, 305-350, Korea, Republic of
AU: Park, K
EM: kgpark@kigam.re.kr
AB: Acoustic televiewer (ATV) has been used to detect the fractures properties which have been intersected by the drilling, and it gives very useful information for the characterization of the fractures such as azimuth, dip, opening, apparent aperture, and so on. Acoustic televiewer, however, tends to interpret fractures larger than real aperture size as well known already. For identifying the applicability and limitation of acoustic televiewer for the characterization of the fractures, 3 inches physical aluminum borehole model has been specially manufactured. The total length of model is 24 centimeters: the intervals of fractures at the dip angle of 0° and 90° extend to 10 centimeters respectively, and the remainder consists of fractures with the different orientation at the dip angle of 30° and 60°. The aperture size is 1, 2, 3, and 5 millimeters, and the depth is the same as aperture size. ATV sonde with main frequency of 1.5 MHz has been used for the data acquisition. And the logging velocity is from 0.1 to 0.9 m/min, the sampling rate per revolution is 360, and number of revolution per second is 20. In case of zero dip angle: There is no vertical resolution in spite of very small logging velocity of 0.1 m/min. The amplitude and travel time data represent 6 millimeters or more regardless the aperture sizes. The vertical resolution in the case of the logging velocity of 0.9 m/min seems to be good compared with 0.1 m/min. But, the vertical resolution for quantitatively estimating the aperture size of fracture with the dip angle of zero is thoroughly very low considering the principle of the measurement. In case of vertical dip angle: The travel time data tends to make it larger 20 percents than the aperture size of model under the velocity of 0.2 m/min and 360 scan, and the amplitude data enlarges over 50 - 60 percents. In case of dip angle 30°: Though the aperture size has been detected larger than model under 3 - 5 millimeters, the estimation of aperture size is possible. But the case of 1 and 2 millimeters is not. In case of dip angle 60°: Though the aperture size has been detected larger than model under 2, 3, 5 millimeters, the estimation of aperture size is possible. This result which the resolution for estimating fracture aperture size is low when dip angle is low more, is very good correlation with the results of ATV application for the 3 inches boreholes located in seawater intrusion zone of Yeonggwang- gun, Jeonnam, South Korea.
DE: 1835 Hydrogeophysics
SC: Near-Surface Geophysics [NS]
MN: 2007 Fall Meeting