The 10th International Symposium on Recent Advances in Exploration Geophysics (RAEG 2006)

Modern technology of prestack depth migration brings directly depth section from seismic data acquired in the time domain. However, practical methods of time to depth conversion from time structure interpretation survive because of its flexibility in handling velocity and cost performance. One of the frequent problems in time-depth conversion is depth mistie at well markers. The more the well, the more complicated technique needs to be considered to solve the entire mistie. We introduce to solve the mistie issue in depth conversion by use of Geostatistics on to well check shot data, which guarantees to maintain the input data unchanged after spatial estimation. In addition to utilization of Geostatistics for conversion velocity estimation, we introduce error estimation criterion to evaluate the estimated velocity for the conversion. This criterion is evaluated comparing velocity variation at well markers. After the estimation of 3D velocity from available check shot data using Kriging approach, we evaluate velocity error distributions by means of sequential Gaussian simulation methods and extract the reliable part of velocity from the criterion. This extracted velocity data and well velocity data are integrated for final depth conversion. We estimate three realizations of velocity error distributions, which give us 3 realizations of final velocity models. The results of depth conversion by those 3 velocity models vary the depth structure within 170 meters or 7% variation at average depth of 3000 meters structure. This 7% variation can be considered as the structural uncertainty after depth conversion except for the well locations in this sturdy.

Seismic interferometry can reconstruct reflection responses by cross-correlation of transmission responses on the surface. An advantage of this method is that we can simulate as many shot records as there are receivers with only one shot record. We applied this method to inverse VSP data acquired by one explosive source in the subsurface at a civil construction site in Mizunami, Japan. From the observed transmission records, shot gathers are reconstructed applying the cross-correlation, and following data processing including poststack migration we obtain a two-dimensional subsurface image. This section is clear enough to evaluate subsurface structures.

IP method has ability of providing valuable information about the structural and hydraulic nature of porous media and fluids contained with such media. To date most IP interpretation technique uses only the chargeability property. In principally IP can give more valuable information about subsurface structure. Using complex resistivity (conductivity) approach, it provides the improved lithological characterization, since surface polarization effects are separated from electrolytic and surface conduction effects. In this study, we develop IP inversion technique using complex resistivity and expand it to the multi-frequency data set. Inverting multi-frequency data set with appropriate object function, it may enhance the noise characteristics of whole data set and enable more accurate estimation of hydraulic and structural parameters.

Waste at controlled landfill disposal sites is a potential cause of environmental pollution or risk and the detection of leakages through man-made liners in waste disposal site has become increasingly important in the last few years. We applied the electrical survey technique to develop a simple and convenient system to detect leakages in waste disposal site with man-made liners. The leakage detection system, which uses permanently installed electrode array under the liner, detects effectively an electrical potential distortion caused by perforations in the liner. Moreover, the potential data obtained under the liner was transformed into a relative current data which has better resolution in locating the leakage point. Also, we developed a simple weighting method which can estimate quantitatively the amount of leakages.

An element free Galerkin method which does not require connectivity between elements and nodes is examined its efficiency for rock experiment. In this study, unconfined compressive test and biaxial test are performed. In this process, the rock specimen is assumed to heterogeneous assigned by Weibull distribution. Acoustic Emission which is microscopic behavior of the specimen agrees with UCS. And failure mode of the specimen also agrees with general laboratory test results. Next, macroscopic behaviors of the specimen which is Young’s modulus, UCS, cohesion, internal friction angle are examined unconfined compression test and bi-axial test. These macroscopic parameters show the tendency has been to increase with an increase in shape parameter.

Multi-component GPR system is developed. It is a part of integrated electromagnetic survey system. The GPR system has four antennas and is able to measure with four antenna patterns. Two field tests are conducted. First test was conducted to analyze the effect of angles between target, steel pipes, and survey line with two directional parallel antennas. Hyperbolic shapes of reflections in data differ by the angles, 0, 30, 60 and 90 degree. Two parallel antennas compensate each result at any survey direction. Summation of two pair of antenna improved the results. Second field was conducted to evaluate the multi-component migration. It is not big different for angle 0 configuration. However two component migration improved the image for angled configuration.