3D Microseismic Source Location via Offset Well DAS Cable
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Solution Overview
Problem
Fiber optic distributed acoustic sensing (DAS) cables used for microseismic monitoring in the hydrocarbon production industry lack broadside sensitivity, resulting in non-unique source-location determination of microseismic events, which limits the interpretive value of fracture geometry parameters.
Innovation Solution
A method utilizing a single acoustic sensing cable to infer three-dimensional locations of microseismic events and calculate fracture geometry parameters by correlating microseismic events with fracture planes, employing a catch percentage parameter and intersecting locus rings with assumed fracture planes to reduce ambiguity in source-location determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a DAS cable is used for microseismic monitoring, then cost and operational advantages are achieved along with longer sensing aperture and denser spatial sampling, but broadside sensitivity is lost resulting in non-unique source-location determination
Solution Approach 1:
The patent uses an offset well as an intermediary structure to deploy the DAS cable at a location separated from the treatment well. This geometric arrangement allows the DAS cable to detect microseismic events from multiple angles, effectively using the offset well as a mediator to overcome the single-directional sensitivity limitation of DAS technology.
Solution Approach 2:
The patent transitions from two-dimensional source location (horizontal plane only) to three-dimensional source location by incorporating vertical depth information. This is achieved by using arrival time differences at multiple sensor locations along the DAS cable and applying wave propagation models to calculate depth, thereby adding the vertical dimension to resolve the non-unique source location problem.
2Ease of operation
If a single straight portion of DAS cable is available, then deployment simplicity is maintained, but the exact source-location of microseismic events becomes undefined
Solution Approach 1:
The patent divides the monitoring system into two independent but complementary components: (1) a DAS cable deployed in an offset well for detecting microseismic events, and (2) a separate fracture detection system that uses the detected events to characterize fracture geometry. This segmentation allows each component to be optimized independently while achieving the overall goal of accurate fracture characterization.
Solution Approach 2:
The patent resolves the source location ambiguity by adding the vertical depth dimension. Instead of attempting to improve horizontal resolution alone, the system uses arrival time analysis and wave propagation modeling to calculate the vertical position of microseismic events, transforming the problem from 2D to 3D space and enabling unique source location determination.
3Device complexity
If DAS cable lacks directional polarization sensing, then device complexity is reduced, but interpretive value of microseismic results is significantly reduced
Solution Approach 1:
The patent employs computational algorithms as intermediaries to extract fracture geometry information from the limited DAS data. These algorithms analyze arrival times, amplitude ratios, and spatial distributions of microseismic events to infer fracture orientation and geometry, effectively using computation as a mediator to compensate for the lack of direct directional polarization measurements.
Solution Approach 2:
The patent performs preliminary characterization of the offset well geometry and seismic velocity model before conducting microseismic monitoring. This preliminary work includes determining wellbore trajectory, calculating expected wave propagation paths, and establishing reference models. By preparing these foundations in advance, the system maximizes the interpretive value of the DAS data without requiring complex real-time processing during events.
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 approach allows for the derivation of accurate three-dimensional microseismic event clouds and fracture geometry parameters, enhancing the accuracy of fracture geometry estimation despite the limitations of DAS cable sensitivity.
Implementation Method 1
a collection of P-wave and S-wave arrival time values from a microseismic event are received from the acoustic sensing cable
Data Source
AI summary
The disclosure is directed to a method of utilizing an acoustic sensing cable, such as a fiber optic distributed acoustic sensing (DAS) cable, in a borehole to detect microseismic events and to generate three dimensional fracture plane parameters utilizing the detected events. Alternatively, the method can use various categorizations of microseismic data subsets to generate one or more potential fracture planes. Also disclosed is an apparatus utilizing a single acoustic sensing cable capable of detecting microseismic events and subsequently calculating fracture geometry parameters. Additionally disclosed is a system utilizing a processor to analyze collected microseismic data to generate one or more sets of fracture geometry parameters.