Thickness measuring of modeled oil-saturated rock with nanosecond bohole electromagnetic loging tool

The paper presents the experimental results of sounding a wet sand-air interface using a laboratory model of a borehole GPR. For this purpose a box filled moist sand moisturized with brine was built. The box was located in a laboratory room on a concrete screed. Radar antennas were housed in a waterproof plastic pipe on the bottom of the box. Radar antennas were made in the form of dipoles with extended bandwidth. The transmitting antenna was connected to the generator, the receiving antenna to the stroboscopic oscilloscope. With variation of thickness of a sand layer over the antennas and the distance between the transmitting and receiving antennas the signals of receiving pulses were recorded. An attenuation coefficient of amplitude and propagation velocity of broadband pulse were measured. It is shown that the theoretical model borehole GPR, created by authors using the method of discrete sources, well predicts a temporary shape and time delay of the pulse reflected from the boundary layer. A method for determining the thickness of the layer of wet sand from the measured time delay of the pulse reflected from the boundary layer at different distances between the transmitting and receiving antennas radar was proposed. This method allows to determine the distance to the interface with a relative error of 2.2 % without the involvement of a priori information on the electro physical properties of the medium in the layer. The results of this study allow you to plan and start bench testing of prototypes borehole probes.