Objetivo In 'no seismic record' areas transient electromagnetic soundings can provide information of the subsurface structure. Our aim is the development of a transient EM field system including a portable receiver, field application, development of data processing and interpretation techniques. This work is to be carry out in conjunction with the oil industry in order to directly evaluate the potential application of the technique.The developed hardware consists of a grounded wire transmitter, a portable, DC operated digital data acquisition system, data processing and interpretation workstation which is being used to produce the preliminary in-field interpretation. Major developments and improvements were done for all parts of the hardware.The entire hardware was tested from the very beginning to the very during test surveys in the field.The data processing was completely redesigned and successfully tested using a pre-stack data processing system. This system significantly increases the signal-to-noise ratio. During all stages of the processing, quality control routines can be run, thus testing the reliability of the data.In order to adjust the developed technology to related exploration problems within the European Community, several numerical feasibility studies were conducted for exploration problems ( hydrocarbon and geothermal) in several countries of the European Community.A new approach of further improving the signal-to-noise ratio has been developed and tested. We call this approach "local noise compensation" which is being done by maintaining a base station during an entire survey day as reference station. Mobile receivers are then moved around in a vicinity of that base station. Under the assumption that the noise does not very much spatially the field data of the mobile receivers can be subtracting the noise derived at each particular time of the day at the base station.The interpretation of the transient electromagnetic data was improved by adding a statistical inversion package to the interpretation which gives error bounds of the individual earth model parameters. Also three dimensional modelling was done to test particularily anomalous transients. The three dimensional modelling of specific problems can either be done using numerical modelling techniques such as integral equations or reduction of the surface anomaly onto a thin latteraly inhomogeneous conductive plate.With these techniques we were able to simulate several phenomenons which we have observed in the field such a sign reversals during he measurement time of the signal.During all phases of the project these techyniques were successfully tested in the field by carriying out field surveys over several geophysical targets. These targets included immediate exploration targets as well as geophysical comparative studies.In almost all cases the results compared very well with other geophysical/geological informations giving us confidence in our development.The project is divided into hardware, data processing, interpretation, and technology transfer tasks. The hardware development included improvements and/or completely new developments of parts of the entire field system. A transient electromagnetic field system consists of a grounded wire, high current transmitter, a portable receiver and a data processing and interpretation workstation which is used for the in-field data processing and preliminary data interpretation. The development of data processing techniques included the design, building and testing of a complete pre-stack data processing system which allows us to obtain a sufficient signal-to-noise ratio even in Western Europe. The research conducted on the interpretation part of transient electro-magnetic data included improvements of the inversion to obtain for the interpreter inversion statistics and error bounds of the individual earth model parameters, three dimensional numerical modelling, and three dimensional analogue scale modelling. Strong collaboration with the oil industry and other scientists helped to obtain the necessary feedback for the system design and specification. During all phases of the project, field tests were done to check hardware, data processing and interpretation schemes. Programa(s) ENG-HYDROCARB 1C - Programme (EEC) of Community projects in the hydrocarbons sector, 1973-1985 Tema(s) 1.4 - GEOPHYSICS AND PROSPECTING Convocatoria de propuestas Data not available Régimen de financiación DEM - Demonstration contracts Coordinador UNIVERSITY OF COLOGNE Aportación de la UE Sin datos Dirección INST FOR GEOPHYSICS AND METEOROLOGY ALBERTUS-MAGNUS-PLATZ 5000 Köln Alemania Ver en el mapa Coste total Sin datos
