06 Patent-US5530359A-Borehole-Logging-Reflected-EM-Signals 1996
US Patent 5,530,359, filed in 1995 and issued in 1996, discloses a borehole radar logging tool that determines both the distance and azimuthal direction of subsurface reflecting structures without mechanically rotating the antenna. The invention replaces the prior‑art directional antenna that required rotation with a circular array of receiver elements (typically linear dipoles housed in corner isolators filled with high‑dielectric material) arranged symmetrically around the tool’s longitudinal axis. By measuring the signal difference between pairs of elements, the tool extracts directional information using a simple analytical relationship \(S{nm}(\theta,\phi) \propto |1-e^{-ikd{nm}\sin\theta\cos\phi_{nm}}|\). The tool can be implemented as a conventional wireline logging system or as a logging‑while‑drilling (LWD) bottom‑hole assembly, with integrated power, compass, and telemetry. The patent details the mechanical construction (corner reflectors, absorbing plates, high‑dielectric loading), the electronic architecture (difference‑measuring devices or software differencing), operating frequencies (≈40 MHz center, up to 120 MHz, with optional phased‑array operation near 300 MHz), and the method for converting measured differences into azimuthal direction. Twenty claims define the essential elements, including the symmetric receiver array, linear dipole elements, difference‑measurement means, direction‑determination logic, and LWD integration. The invention enables full‑azimuth coverage, higher signal‑to‑noise ratio, and eliminates the need for rotating hardware, improving reliability and measurement speed for applications such as reservoir characterization, geo‑steering, and fracture detection.
Topics
Core Innovation: Circular Receiver Array with Pairwise Differential Measurement
Introduces the central concept of arranging multiple receiver elements around the tool axis and extracting direction by measuring signal differences between element pairs.