Microseismic Receiver Positioning Using Thales Circles
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In microseismic monitoring, particularly in hydraulic fracturing operations, the precise location of receivers within subterranean boreholes is challenging due to uncertainties in receiver positions and orientations, leading to errors in event location determination.
Innovation Solution
A method that determines the horizontal position of seismic receivers by analyzing the back-azimuth of seismic events using particle polarization and constructing Thales' circles from known event locations, which can be combined with travel-time measurements for enhanced accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If receiver positions are determined using cable depth and deviation surveys, then receiver locations can be obtained, but uncertainties in position and orientation lead to errors in event location determination
Solution Approach 1:
The method uses observed seismic events with known locations to provide feedback on the actual receiver positions. By comparing the observed back-azimuths and arrival times with those expected from assumed receiver positions, the system iteratively adjusts and refines the receiver location estimates, eliminating initial uncertainties from cable depth and deviation survey measurements.
Solution Approach 2:
The monitoring array determines its own positions autonomously by utilizing the seismic events it observes. Instead of relying on external survey methods, the system uses the seismic data itself (back-azimuths and arrival times from events with known locations) to self-correct and precisely locate the receivers, making the system self-calibrating.
2Measurement precision
If multiple seismic events are used to determine receiver position, then position accuracy improves, but the complexity of the method increases
Solution Approach 1:
The method segments the determination process into distinct computational steps: calculating back-azimuths from observed waveforms, constructing Thales' circles based on back-azimuth differences, and using arrival times to refine positions. This segmentation makes the complex problem of multi-event location determination manageable and systematic.
Solution Approach 2:
The method transitions from two-dimensional back-azimuth information (direction only) to three-dimensional position determination by incorporating the third dimension of arrival time. Thales' circles provide 2D location constraints, and adding arrival time data from multiple events resolves the vertical position, achieving full 3D receiver localization.
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 method reduces uncertainties in receiver positions, improving the accuracy of microseismic event location determination and fracture geometry analysis in hydraulic fracturing monitoring.
Implementation Method 1
determining the back azimuth of the seismic events and for that makes preferably use of the particle polarization of seismic waves emanating from spatially distributed seismic events
Data Source
AI summary
A microseismic method of determining the position of a downhole receiver (4) making use of received signals from events (21, 22) at least two known locations using the equivalent of a Thales circle construction from two or more pairs of events.