Experimental validation of the wavefield transform
- Univ. of California, Berkeley, CA (United States)
The advent of sophisticated electromagnetic data brought with inversion techniques it stringent demands for for interpreting subsurface improvements in the accuracy and fidelity of measurements. In particular the wavefield transformation technique makes it possible to map the interwell distribution of electrical conductivity if the data is noise-free over a large bandwidth. In that case it becomes possible to form a tomographic image of the subsurface section bounded by two vertical boreholes. In this technique the diffusive low frequency EM field is numerically transformed to a mathematically defined space where it. constitutes a wavefield. dependent on the conductivity of the The resultant pulse has a medium. Thus, an image velocity which is of the subsurface distribution of electrical conductivity can be constructed using a non-linear ray tracing technique normally reserved for seismic velocity tomography (Lee and Xie, 1993) A fully computerized laboratory scale time domain data acquisition system has been designed and used to simulate subsurface crosswell and borehole-to-surface experiments in a horizontally layered earth model. The model is made of two cylindrical blocks of graphite with an electrical conductivity of 9.4X104 S/m and 1.4 m in diameter. Steel , sheets with a conductivity of 1.39 X106 S/m and 1.2 mm thick are also used. This model has been linearly scaled down from field dimensions by a factor of 1000. The conductivity has been scaled up by a factor of 106. The time scale is unity. The acquired laboratory scale model data were successfully transformed to the wavefield domain. Thus the practicaI feasibility of the wavefield transform technique was established. In the course of this process it was observed that the system bandwidth is a crucial parameter affecting data fidelity.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 760288
- Report Number(s):
- LBNL-42409; R&D Project: 731001; TRN: AH200103%%46
- Resource Relation:
- Other Information: TH: Thesis (M.S.); Submitted to University of California, Berkeley, CA (US) Department of Materials Science and Mineral Engineering; PBD: 1 Dec 1996
- Country of Publication:
- United States
- Language:
- English
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