Sonic Logging Tool Isolator for Dipole Measurement Precision
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Solution Overview
Problem
Conventional sonic logging tools face challenges in accurately characterizing unconventional reservoirs, such as shale gas and oil formations, due to interference between tool intrinsic modes and borehole modes in horizontal or high-angle wells, and require a balance between mechanical strength and flexibility to avoid contamination of dipole measurements.
Innovation Solution
The sonic logging tool design includes individual acoustic receiver modules with sensors, amplifiers, and A/D converters encapsulated near the outer diameter, an isolator section functioning as a mass and spring system with a mandrel of alternating diameters, and a perforated sleeve to minimize tool interference and allow for high-quality dipole and monopole measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the tool diameter is reduced to enable deployment in horizontal or high-angle wells, then adaptability to well configurations is improved, but measurement precision deteriorates due to increased tool interference and intrinsic mode contamination
Solution Approach 1:
The tool is divided into separate acoustic source and receiver sections with an isolator section between them. The isolator section is segmented into alternating portions with different outer diameters, creating a mechanical band-stop filter that segments the frequency spectrum and blocks tool intrinsic modes from contaminating the dipole measurement bandwidth.
Solution Approach 2:
An isolator section functioning as a mechanical band-stop filter is introduced as an intermediary between the acoustic source and receiver sections. This isolator blocks the propagation of tool intrinsic modes while allowing formation acoustic signals to pass through, thereby protecting measurement precision without requiring a larger tool diameter.
2Reliability
If the isolator section is designed with alternating portions to function as a mechanical band-stop filter, then tool interference is reduced, but device complexity increases
Solution Approach 1:
The isolator section serves multiple functions simultaneously: it provides mechanical isolation between source and receiver sections, acts as a band-stop filter to block tool intrinsic modes, and maintains structural integrity of the tool assembly. This multi-functionality reduces the need for separate components, thereby limiting the increase in device complexity while improving measurement reliability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enables high-quality dipole sonic measurements with a smaller outer diameter tool, reducing interference from tool intrinsic modes and allowing for accurate detection of pressure differences, essential for effective characterization of anisotropy and fracture evaluation in horizontal wells.
Implementation Method 1
The isolator section can be configured to function acoustically as a mass and spring system. For example, the isolator section can include a mandrel having alternating portions with different outer diameters.
Implementation Method 2
Additionally, the mandrel can be configured to function acoustically as a mechanical band-stop filter. For example, a center frequency and/or a bandwidth of the mechanical band-stop filter can be related to respective sizes of the first and second portions of the mandrel.
Implementation Method 3
Each acoustic receiver module can include a transducer element that is configured for detecting acoustic signals
Data Source
AI summary
A tool for monopole and multipole sonic logging includes an acoustic source section, an acoustic receiver section, and an isolator section disposed therebetween. The tool may include a mandrel having integrally formed alternating first portions having a first outer diameter and second portions having a second outer diameter. The second outer diameter is smaller than the first outer diameter, which allows the portions to function acoustically as a mass and spring system. The isolator section sufficiently mutes or delays extensional and flexural modes intrinsic to the logging tool itself. Thus, the effects of the tool presence on the measurements are minimized. In addition, a plurality of axially oriented grooves are defined in an outer surface of the acoustic receiver section, and each groove is configured for receiving an acoustic receiver module that includes a sensor, an amplifier, an A/D converter, and a digital multiplexer.