Development of a Dual Mode Ground Penetrating Radar (GPR) for Deep Imaging to the Sand Dunes and Weathering Layers Thickness
Almutairi, Khaled F.*1; Alkhalifah, Tariq 1; Utsi, Vincent P.2
(1) Oil& Gas Institute research, KACST, Riyadh, Saudi Arabia. (2) Utsi Electronics Ltd., Utsi Electronics Ltd., Cambridge, United Kingdom.
A low frequency Ground Penetrating Radar has been developed and, more particularly, a dual mode GPR. The dual mode operation interleaves a short transmit pulse with a sequence of longer spread spectrum pulses. The dual mode GPR allows for rapid measurement and imaging the geological structures or layer depths, such as sand dunes more than 120m depth, and weathering patterns of geological features. Further, the antenna of the dual mode GPR arrangement allows for measurement in harsh environmental conditions and, advantageously, can achieve its resistive loading without the use of resistors that force the antenna to be excited at its midpoint. Instead, this system uses ferrite rings with specific characteristics to provide the resistive loading.
This very low frequency ground penetrating radar is used with a unique antenna configuration, mounting arrangement and transmitter control. A low frequency in combination with pulse compression technology provides improved depth capability over conventional antennas. Specifically, the GPR of the present invention uses a 5 to 15MHz frequency range, which is lower than commercially available GPR systems. This low frequency has a long wavelength which attenuates less in sand than higher frequencies. Further, the receiver of the antenna has higher sensitivity because it performs real time analog-to-digital conversion and a field-programmable gate array (FPGA) for signal processing.
The developed GPR provides knowledge of sand dunes and weathering layer depths for accurate interpretation of seismic data used, for example, by the oil exploration industry, mining industry, geotechnical investigations and groundwater exploration. For that, it becomes an important tool in the petroleum industrial world to improve the quality of land seismic data and reduce the effects of irregularities within the near surface.
AAPG Search and Discovery Article #90141©2012, GEO-2012, 10th Middle East Geosciences Conference and Exhibition, 4-7 March 2012, Manama, Bahrain