Dynamic Fracture Monitoring Technique in Deep Coal Seams Based on a Time-Varying Electric Field Method.

Area of Science:

• Geophysics
• Petroleum Engineering
• Reservoir Engineering

Background:

• Deep coalbed methane (CBM) development is hindered by poor understanding of hydraulic fracture propagation.
• Existing monitoring methods lack the real-time, high-resolution data needed for accurate stimulation evaluation.

Purpose of the Study:

• To introduce and validate a novel dynamic fracture monitoring technique for deep CBM reservoirs.
• To improve the characterization of hydraulic fracture growth and fluid migration during stimulation.

Main Methods:

• Development of a coupled electric field-fracturing fluid flow model.
• Deployment of a high-density downhole electrode array with real-time data processing.
• Application of dynamic inversion for fracture geometry and fluid distribution analysis.

Main Results:

• The technique achieved millisecond-level signal acquisition and dynamic fracture tracking with 0.5 m spatial accuracy and <5 min temporal resolution.
• Quantified three-stage fracture behavior (initiation, extension, reorientation) with maximum fracture length of 214.95 m.
• Identified stress-extended zones not reached by fracturing fluid, indicating reservoir heterogeneity.

Conclusions:

• The time-varying electric field method provides accurate, real-time monitoring of hydraulic fractures in deep CBM reservoirs.
• The findings enable better evaluation of stimulation effectiveness and optimization of fracturing designs.
• This contributes to overcoming challenges in deep coal seam development and production.