Porosity & Permeability, Fluid Flow, Resistivity
HYDROGEOLOGY
Magnetic Resonance
Features
- Measure porosity & pore size (in saturated zone)
- Measure saturation (in unsaturated zone)
- Calculate permeability, bound vs free fluid
- Distinguish between water, oil & gas
- Does not require a nuclear source
Applications include:
- High-resolution packer test infilling
- Leach pad optimization
- Tailings dam hazard analysis
- Monitor dewatering progress
- Well screen placement
- Coal gas content
- Grain size estimation
Above: Magnetic Resonance permeability log is shown in brown below, compared with 5 m packer intervals in light green. Dark green is NMR permeability averaged over the packer interval, and red is core permeability. As is evident, NMR permeability agrees well with packer tests, while offering much higher resolution. Above is the total porosity measured by NMR, subdivided into free fluid (blue), capillary fluid (yellow), and bound fluid (grey). Purple bars are porosity from core.
Above: NMR matches pump test results well; reads lower porosity than core due to lack of confining pressure in core analysis.
Above: NMR can measure free and adsorbed gas and oil content, with rapid turnaround as compared with traditional methods.
Dual Neutron
- Measures water content (porosity) downhole
- Uses a nuclear source
- Cannot determine pore size or permeability estimate
Fluid Flow
Spinner and Heat-Pulse Flowmeter
- Measure flow rates under ambient and pumping conditions
- Locate in/out flow zones and rates
- Spinner Flowmeter for high-flow or pumping conditions
- Heat-Pulse Flowmeter for low-flow or ambient conditions
Above: Schematic illustration of hypothetical flow regimes measured under ambient and pumping conditions.
Above: The bar chart to the left and well schematic on the right, show inflow and outflow rates measured with Heat-Pulse Flowmeter under ambient conditions. The logs in the center show rates measured by Spinner Flowmeter under pumping conditions. The difference above and below each step in these curves are the inflow rates, shown in the bar chart to the right. Fluid temperature/conductivity logs also provide qualitative indication of inflow/outflow zones due to differences in fluid properties between inflowing formation water and borehole water post-drilling.
Fluid Temperature & Conductivity
- Locate flow zones downhole via differences between inflowing formation water and borehole water post-drilling.
- Combine with Flowmeter for flow confirmation (see above)
Nuclear magnetic resonance
Quantitative flowmeter
Temperature
Resistivity
Elog
- Identify fracture zones below water table
- Combine with Caliper and/or Televiewer for fracture confirmation
Cross-Hole Resistivity
- Image fluid flow with excellent depth resolution.
- Contaminant plume migration
- Leach pad flow pathways
- Tailings dam saturation profiles
- Also used with cross-hole IP for mineral exploration
Above: Cross-hole resistivity profile of a low-resistivity anomaly, such as a contaminant plume, leachate flow pathway, or mineralization.