Production Enhancement

Distributed Fiber Optic Sensing

1. Overview

Distributed Fiber Optic Sensing (DFOS) is an advanced measurement technology that uses optical fibers as continuous sensing elements to monitor physical parameters such as temperature, strain, vibration, and acoustic energy along the entire length of the fiber. Unlike traditional point sensors, DFOS provides fully distributed measurements with meter- or even centimeter-scale spatial resolution over distances of several kilometers.

DFOS operates by detecting and analyzing light scattering phenomena — primarily Rayleigh, Brillouin, or Raman scattering — that occur when a laser pulse propagates through the optical fiber. Variations in the backscattered light correspond to changes in strain or temperature along the fiber, allowing the system to construct a continuous profile of the monitored structure or formation.

  • DAS (Distributed Acoustic Sensing): Measures acoustic vibrations and is widely used for seismic imaging, microseismic monitoring, and flow detection.

  • DTS (Distributed Temperature Sensing): Provides continuous temperature profiles for reservoir, wellbore, or pipeline monitoring.

  • DSS (Distributed Strain Sensing): Detects deformation, stress, or bending in wells, pipelines, and structures.

  • DTGS (Distributed Temperature and Gas Sensing): Combines temperature sensing with gas detection for enhanced safety and environmental monitoring.

2. Applications in Energy and Geoscience

  1. Reservoir and Wellbore Monitoring – Continuous profiling of temperature, pressure, and flow in horizontal or vertical wells to optimize production and detect water or gas breakthrough.

  2. Seismic and Microseismic Monitoring – Using DAS for Vertical Seismic Profiling (VSP), cross-well imaging, or passive seismic detection, offering real-time insight into subsurface dynamics.

  3. CO₂-EOR and CCUS Projects – Tracking CO₂ plume migration, monitoring caprock integrity, and ensuring long-term storage security through temperature and acoustic response analysis.

  4. Pipeline and Infrastructure Integrity – Detecting leaks, intrusions, and mechanical strain to prevent failures and enhance operational safety.

  5. Geotechnical and Environmental Monitoring – Measuring strain, vibration, and temperature in tunnels, dams, slopes, and geothermal reservoirs for stability and environmental management.

3. Advantages

  • Continuous, real-time monitoring over long distances

  • High spatial and temporal resolution

  • Immunity to electromagnetic interference

  • Robust operation in harsh environments

  • Cost-effective when deployed as multi-parameter sensing systems

Microseismic Monitoring

1. Overview

Microseismic monitoring is a geophysical technique used to detect and analyze small-magnitude seismic events (microearthquakes) generated by subsurface processes such as hydraulic fracturing, CO₂ injection, geothermal stimulation, or reservoir compaction.
It provides real-time information on fracture propagation, fluid migration, and stress redistribution, enabling a better understanding of reservoir dynamics and stimulation effectiveness.

The method is non-invasive and allows continuous monitoring of subsurface activity over large spatial and temporal scales, serving as a key component of reservoir surveillance, CCUS integrity assessment, and unconventional resource development.

2. Principles of Microseismic Monitoring

Microseismic events are small stress releases (typically magnitude −3 to +1) caused by rock deformation or fracturing.
Each event generates P- and S-wave arrivals, which are recorded by arrays of geophones, accelerometers, or fiber-optic sensors placed in boreholes or on the surface.

By analyzing the arrival times, amplitudes, and waveforms at multiple receivers, the event hypocenter (x, y, z) and origin time (t₀) can be determined through triangulation and inversion algorithms.
These event locations collectively define the fracture geometry, stimulated rock volume (SRV), and potential fluid flow pathways.

3. System Configuration

A typical microseismic monitoring system consists of the following components:

  • Downhole or Surface Sensor Arrays:

    • Downhole arrays: Deployed in observation wells close to the treatment zone (1–3 km depth), providing high signal-to-noise ratios.

    • Surface or shallow arrays: Used when well access is limited, covering a broader area but with lower resolution.

    • Fiber-optic Distributed Acoustic Sensing (DAS): Offers continuous acoustic measurements along the entire fiber length, allowing real-time distributed monitoring without point sensors.

  • Data Acquisition System (DAS/DTS/DxS):
    High-speed recording units with precise time synchronization (GPS or atomic clock) capture full-waveform data during injection or stimulation.

  • Processing and Analysis Software:
    Advanced algorithms perform event detection, picking, location, magnitude estimation, moment tensor inversion, and visualization in 3D fracture mapping.

  • Telemetry and Control:
    Real-time data transmission allows continuous monitoring during field operations, enabling rapid decision-making for injection control.

4. Data Processing and Interpretation

  1. Event Detection: Identify microseismic signals above background noise using STA/LTA or machine-learning filters.

  2. Phase Picking: Determine precise P- and S-wave arrival times for each event at multiple sensors.

  3. Event Location: Triangulate hypocenter positions using travel-time inversion methods.

  4. Magnitude and Source Mechanism Analysis: Calculate seismic moment, magnitude, and moment tensor to infer fracture orientation and stress regime.

  5. 3D Visualization: Plot event clouds to delineate fracture networks, stimulated volume, and zones of deformation.

Microseismic data are often integrated with pressure, injection, and geomechanical models to assess stimulation effectiveness and reservoir response.

5. Applications

  • Hydraulic Fracturing:
    Real-time mapping of fracture growth, orientation, and height containment; optimizing stage spacing and treatment design.

  • CO₂-EOR and CCUS:
    Monitoring injection-induced seismicity and verifying storage integrity by detecting potential caprock breaches or fault reactivation.

  • Geothermal Reservoirs:
    Tracking fracture creation and heat-exchange zone development.

  • Reservoir Compaction and Depletion:
    Detecting deformation or micro-faulting associated with long-term production.

  • Wastewater and Acid Gas Injection:
    Ensuring safe injection practices and early detection of abnormal pressure buildup or induced seismic risk.

6. Advantages

  • Non-invasive and continuous subsurface monitoring.

  • Provides real-time feedback on fracture propagation and reservoir response.

  • Enables 3D mapping of the stimulated reservoir volume.

  • Integrates with fiber-optic sensing (DAS/DTS) and geomechanical models for multi-physics interpretation.

  • Assists in risk management, ensuring operational safety and compliance with regulatory frameworks.

7. Summary

Microseismic monitoring is a powerful diagnostic tool for understanding fracture development, reservoir stimulation efficiency, and CO₂ storage behavior.
It bridges geophysics and reservoir engineering by transforming seismic event data into actionable insights about reservoir structure, integrity, and dynamic behavior.

When integrated with fiber-optic distributed sensing, pressure monitoring, and reservoir simulation, microseismic analysis enables a comprehensive, real-time view of subsurface processes essential for optimizing EOR, CCUS, and unconventional reservoir development.