Single Borehole Radar for Well Logging in a Limestone Formation: Experiments and Simulations

Abstract

A borehole radar (BHR) prototype system was developed for the exploration of complicated oil and gas reservoirs. To verify the performance of the system, single-hole reflection imaging experiments were carried out in an abandoned limestone mine. In the physical experiments, the cliff wall and a metal plate were selected as the imaging targets to evaluate the detection performance of the prototype system. The average filter method was used to remove the background noise, then the frequency–wave number (F-K) imaging algorithm was adopted for radar imaging. The unknown fractures surrounding the borehole produced complex reflections that were not beneficial to effectively extract the target echo when the down-hole sensor was shifted along the borehole. However, by fixing the down-hole sensor and shifting the target, the detection range of the radar system extended up to about 10 m in the limestone formation. A 2-D finite-difference time-domain (FDTD) modeling method was also implemented to simulate the experimental procedure, and demonstrated that the prototype system can provide enough accuracy to predict the echo signal characteristics and reproduce the radar response in the formation. The combination of field experiment, theoretical analysis, and numerical simulation not only objectively validated the fundamental performance of the radar prototype, but also generated some new concepts for further improvement on the radar system design.

Consideration of Oblique Incidence in 3-D Imaging of a Planar Interface With a Circular Dipole Array in an Air-Filled Borehole

“…In Fig. 4, we find that the CEA, 180-rc, intersects the curve of r at only one point since the curve rc increases monotonically as seen in (8). Now, we define the critical receiver position rc z (CRP) as the location where the reflected wave is incident on the receiver at CEA.…”

“…Field experiments have proved that a singlehole borehole radar can image water-filled fractures in rock and estimate the dip angle of the fractures [6]. The singlehole borehole radar can also produce good images of a cliff [7] [8]. Computer simulations have predicted that a singlehole borehole radar may also be able to detect a planar interface using guided waves along the borehole [9].…”

Estimating reservoir permeability with borehole radar

“…Miorali et al (2011) and Zhou et al (2018) proposed to apply borehole radar to monitor water-oil movement for oil production optimization. A borehole radar logging prototype has been developed with the original intention to image fractures in hydrocarbon reservoirs (Liu et al, 2012;Liang et al, 2012;Ma et al, 2016). The aforementioned borehole radar applications operate at frequencies of a few hundred MHz, which correspond to wavelengths in decimeter to meter range and penetrate the reservoirs in a range of a few meters.…”

Reservoir monitoring using borehole radars to improve oil recovery: Suggestions from 3D electromagnetic and fluid modeling

“…Even deeper applications of GPR technology, for example, hydrocarbon reservoirs at a depth of up to thousands of meters, have been proposed (Chen and Oristaglio, 2002;Heigl and Peeters, 2005). Recently, laboratory experiments have been conducted to emulate the EM response of a wideband radar on the perforations and impairments of an oil well (Oloumi et al, 2015), and a borehole radar prototype system is under development for well logging usage (Ma et al, 2016).…”