The application of Distributed Acoustic Sensing (DAS) technology in the field of well logging has completely revolutionized the traditional method of underground data acquisition. By using the optical fiber itself as a sensor, it enables continuous, real-time and distributed measurement of physical quantities such as acoustic waves, vibrations and temperature in the wellbore, providing unprecedented data support for reservoir characterization, production optimization and effect evaluation of stimulation measures.
1. Core Application Scenarios of DAS in Well Logging
(1) Production Dynamic Monitoring
Main monitoring objects: Liquid production profiles of oil, gas and water layers, production intervals of electric submersible pump (ESP) wells, and water absorption profiles of injection wells.
Technical value and outputs: Identify water breakthrough positions, evaluate the effect of zonal water injection, and provide a decision-making basis for water shutoff operations.
(2) Hydraulic Fracturing Monitoring
Main monitoring objects: Initiation and propagation of fracturing fractures, fluid intake efficiency of each perforation cluster, and inter-well and inter-stage interference.
Technical value and outputs: Optimize fracturing parameters, evaluate the opening status of each cluster, and provide key references for well pattern deployment.
(3) Seismic Exploration and Reservoir Characterization
Main monitoring objects: Vertical Seismic Profile (VSP), cross-well seismic, and microseismic events.
Technical value and outputs: Obtain high-precision near-well velocity models, realize reservoir and fluid imaging, and assist in fault identification.
2. Unique Advantages and Common Technical Combinations of DAS
DAS stands out prominently in the field of well logging due to its disruptive advantages over traditional point sensors.
Distributed measurement: A single optical fiber serves as tens of thousands of continuous sensors, capturing complete information of the entire wellbore with no monitoring blind spots.
Real-time and long-term operation: Capable of uninterrupted testing for an extended period, enabling full-time dynamic analysis and capturing transient events as well as long-term change trends.
High sensitivity and passive characteristics: The optical fiber itself is resistant to electromagnetic interference and corrosion, requiring no downhole power supply, and can operate stably under complex well conditions (e.g., high-yield ESP wells, high-temperature and high-pressure environments).
Diverse technical combinations: In practice, DAS is often combined with Distributed Temperature Sensing (DTS) technology to form an integrated monitoring solution of "DAS + DTS". DTS provides temperature field information, which complements and verifies the acoustic/vibration information from DAS, jointly analyzing the dynamics of downhole fluids to achieve a more comprehensive diagnosis of production conditions.
For example, the "DTS+DAS" system developed by Smarteng Micro has participated in more than 90 optical fiber well logging projects and 26 long-term monitoring projects after years of technological R&D, field implementation and remote services. Its service scope covers a variety of well types including flowing high pour-point oil wells, rod-pumped oil wells, CBM rod-pumped wells, CBM horizontal wells, shale gas horizontal wells, natural gas horizontal wells, natural gas wells, gas storage injection-production wells, CO₂ injection wells, N₂ injection wells and water injection wells, accumulating rich project experience.
3. Development Trends
The future development of DAS technology in the field of well logging is closely linked to the following trends:
- Integration with artificial intelligence and big data: Faced with the massive data generated by DAS, machine learning and artificial intelligence technologies are being widely adopted to automatically identify signals, classify events and extract valuable information.
- Expansion to broader fields: The application of DAS is expanding from conventional oil and gas exploitation to shale gas, geothermal energy, carbon dioxide geological storage and geological disaster monitoring.
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