The aim of the project is to develop a 3D seismic data-acquisition system by radio transmission, which cumulates the advantage of existing systems while avoiding their disadvantages.
- RTU : Full tests of analog acquisition board with analog/digital converter 24 bits; tests of the processing and DSP board; tests of the radio transmitter and receiver; test of reference test generator; development of hardware and software for the PC tester; test of prototype antennas. Tests of 10 RTUs; test of a concentrator (electronic and optical cable)
- DCU : Tests with a specific software to valuate the DCU boards; design of definitive electronic boards (4 boards) of the concentrator.
- CRU : Tests of the wire-wrap prototype DP/M and DC boards; valuation of the main real time operating system software; tests of the interface CRU/DCU board; Data Collector and Dual Processor printed board tested; multitasking software tested; tape tasks tested.
First tests in the field; very good results for radio transmission range and for seismic results.
Second and last test in the field with all the system : 48 tracs, more DCUs and CRU.
A full-size essay carried out in the Orleans foresthas demonstrated the reliability of the radio transmission and the capability of the system to acquire real seismic data.
The project consists in creating a system capable of transmitting, under conditions close to real time, seismic data for 1000 seismic channels on several radio frequencies semisequentially. To achieve this radio transmission, a digital modulation technique will be used to transmit a great density of digital data in a reduced radio-wave spectrum by implementing low power compatible with national regulations. DCUs (data concentrator unit) capable of receiving modulations from about 100 stations will be linked to the CRU either by UHF radio-wave linkage or by a single optical cable, or else by a combination of these two types of linkages, as function of the natural of the ground. The flexibility of the system will also be increased by the possibility of preprocessing the seismic information such as the stacking of shots in acquisition stations (RTUs). The possibility of remote controlling from the CRU of variable transmission velocities suited to different regulations will be a thirdtype of flexibility of the system. A new analog-to-digital conversion concept will be adopted to be able to transform seismic data into a digital form when they are acquired in situ. The different parts of the system will be designed by progressively building, in the laboratory, four mock-ups of RTU telemetering acquisition stations, one mock-up of the DCU and one CRU, DCU. Fields tests will then be undertaken with the aim of being representative of different transmission possibilities between the CRU, DCU and telemetering stations for a POLYSEIS system simulating 1000 seismic channels. These tests will require the development, as part of the POLYSEIS project, of the following pieces of equipment : 60 prototypes of RTUs, 4 DCUs, 2 CRUs.
The project involves 3 phases :
Phase 1 : Feasibility of the POLYSEIS system
Phase 2 : Development of prototype subsets of the POLYSEIS system
Phase 3 : Field tests of the POLYSEIS system.