Downhole Optical Fiber Depth Calibration via Seismic Wave Analysis
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Solution Overview
Problem
Existing depth calibration methods for optical fibres in wells are influenced by the accuracy of OTDR and cable counters, leading to insufficient calculation accuracy and inability to meet current technical needs.
Innovation Solution
A method that performs de-noising on seismic wave field data acquired by optical fibres, compares it with logging data for analysis, and determines depth calibration information to improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If OTDR and cable counter are used for depth calibration, then the calibration process is simple, but the calculation accuracy is insufficient
Solution Approach 1:
The patent introduces seismic wave field data as an intermediary element to bridge the gap between simple calibration methods and accurate depth determination. By using seismic waves that propagate through the formation and are detected by the optical fibre, the system obtains indirect but highly accurate depth information without requiring complex direct measurement equipment.
Solution Approach 2:
The patent replaces the mechanical/electrical measurement systems (OTDR, cable counter) with a seismic wave-based measurement approach. Instead of using optical time-domain reflectometry or mechanical cable counting, the system uses seismic wave propagation characteristics and optical fibre sensing to determine depth, achieving higher accuracy through physical principle substitution.
2Measurement precision
If de-noising processing and seismic wave field data analysis are performed, then depth calibration accuracy is improved, but the processing complexity increases
Solution Approach 1:
The patent applies de-noising processing as a preliminary action before performing seismic wave field data analysis. By preprocessing the raw seismic data to remove noise and enhance signal quality in advance, the subsequent depth calibration calculations can proceed with higher accuracy without requiring overly complex processing algorithms.
Solution Approach 2:
The system uses the optical fibre itself as both the data acquisition device and the measurement sensor. The optical fibre that is already deployed in the well serves dual purposes: transmitting seismic wave field data and providing the measurement medium for depth calibration, eliminating the need for separate calibration equipment and reducing overall system complexity.
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
The method achieves improved depth calibration accuracy by accurately determining the wellhead initial position and receiving point spacing of the optical fibre, providing reliable data support for subsequent analysis.
Implementation Method 1
acquiring borehole seismic wave field data based on an optical fibre acoustic wave sensor
Implementation Method 2
optical fibres are widely used in the field of borehole geophysics
Data Source
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AI summary
Disclosed are a method and device for calibrating the depth of an optical fibre in a well. The method comprises: acquiring borehole seismic wave field data based on an optical fibre acoustic wave sensor; determining first arrival time information based on the borehole seismic wave field data; determining a downgoing wave first arrival amplitude based on the first arrival time information and the borehole seismic wave field data; determining an optical fibre amplitude feature point based on the downgoing wave first arrival amplitude; determining a wellhead initial position and a receiving point spacing of the optical fibre in the well based on the optical fibre amplitude feature point and logging curve feature points; and determining depth calibration information of the optical fibre in the well based on the wellhead initial position and the receiving point spacing. By improving the existing optical fibre depth correction method, after de-noising processing and first arrival pick-up are performed on the borehole seismic wave field data acquired by the optical fibre acoustic wave sensor, the wellhead initial position and receiving point spacing of the optical fibre in the well are determined in combination with existing logging data, so that the depth position of the downhole optical fibre can be calibrated, and the depth calibration accuracy is improved.