Low-Frequency DAS Well Interference Localization
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Solution Overview
Problem
Existing methods for evaluating cross-well interference in unconventional hydrocarbon reservoirs, such as tight-gas sands and shale formations, lack spatial information and are limited by noise and installation issues, leading to inaccurate results and increased operational costs.
Innovation Solution
A method utilizing fiber-optic Distributed Acoustic Sensing (DAS) and Distributed Temperature Sensing (DTS) technologies to detect and analyze low-frequency signals for well interference, employing a data processing workflow to mitigate noise and interference, and using interrogators to collect and analyze data from installed optical fibers in monitor and production wells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pressure monitoring is used to detect well interference, then pressure communication between wells can be examined, but spatial information about connectivity is not provided
Solution Approach 1:
The patent introduces fiber optic cables as an intermediary sensing medium installed in the wellbore. These cables detect acoustic signals and temperature changes caused by cross-well interference, providing both pressure communication detection and spatial location information that neither pressure monitoring alone nor tracer methods can provide
Solution Approach 2:
The patent replaces traditional mechanical pressure monitoring systems with optical fiber-based sensing. The fiber optic cables use optical interference techniques to detect acoustic signals and temperature variations, substituting mechanical measurement with optical measurement to achieve both pressure detection and spatial resolution
2Loss of information
If chemical or radioactive tracers are used, then spatial information about well interference can be obtained, but measurement is limited to early production stages due to limited downhole survival time
Solution Approach 1:
The patent replaces chemical and radioactive tracer methods with fiber optic acoustic and temperature sensing. This substitution eliminates the need for downhole survival of tracer materials, allowing continuous monitoring throughout the entire production lifecycle while maintaining spatial information capability
Solution Approach 2:
The fiber optic sensing system is self-powered and requires no downhole power source or chemical reactions. The optical fibers passively detect acoustic and temperature signals caused by cross-well interference, eliminating the need for active tracer injection and survival mechanisms
3Measurement precision
If DAS data are sampled at high rate with high position accuracy, then critical spatial data for detecting near well bore changes can be obtained, but noise and interference from installation issues reduce measurement accuracy
Solution Approach 1:
The patent extracts and separates the harmful noise components from the DAS signal through sophisticated data processing workflows. Multiple filtering techniques are applied to remove noise from different sources, isolating the true cross-well interference signals from installation-related disturbances
Solution Approach 2:
The patent implements feedback mechanisms where the processed DAS and DTS data are continuously analyzed to improve measurement accuracy. The system uses the high-resolution spatial data to identify and correct for installation-induced noise, feeding this information back into the analysis to enhance overall measurement precision
4Measurement precision
If fiber optic cables are installed for DAS/DTS sensing, then accurate spatially-resolved evaluation of cross-well interference can be achieved, but device complexity and installation costs increase
Solution Approach 1:
The fiber optic cables serve multiple functions: they act as both acoustic sensors (DAS) and temperature sensors (DTS) simultaneously. This multi-functionality reduces the need for separate sensing systems and simplifies the overall installation complexity while maintaining high measurement precision
Solution Approach 2:
The patent merges the acoustic sensing (DAS) and temperature sensing (DTS) functions into a single fiber optic cable system. By combining these sensing modalities, the patent reduces the number of separate installations needed while achieving comprehensive cross-well interference evaluation with high spatial resolution
Data Source
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AI summary
A method of assessing cross-well interference and/or optimizing hydrocarbon production from a reservoir by obtaining low frequency DAS and DTS data and pressure data from a monitor well, when both the monitor and production well are shut-in, and then variably opening the production well for production, and detecting the temperature and pressure fluctuations that indication cross-well interference, and localizing the interference along the well length based on the low frequency DAS data. This information can be used to optimize well placement, completion plans, fracturing plans, and ultimately optimize production from a given reservoir