CASE STUDY: HEAVY OIL EOR

In heavy-oil EOR (steamflood / waterflood), the biggest operational blind spot is the position of the steam or water front between wells. ETI uses Controlled-Source Electromagnetics (CSEM)—designed with 3D feasibility + noise testing and calibrated to well logs—to image fluid/temperature changes away from the wellbore, enabling faster optimization of injection strategy/costs and lower recovery risk. 

The problem EOR teams face

Steam and injected water change the reservoir quickly, but most measurements are either:

• near-wellbore only (production data, and well logs), or
• expensive and not fluid-specific enough day-to-day steering.

ETI’s workflow targets exactly what matters in EOR:

• Where is the front now?
• Is it sweeping uniformly or selectively?
• Is it moving out of zone (caprock risk / thief zones)? 

Why CSEM is a good fit

CSEM is sensitive to electrical resistivity, which changes strongly during EOR with varying water/oil saturation in the reservoir fluid:

• Steam/temperature effects can drive large resistivity changes (~150 % resistivity change for a 100 °C temperature increase). 
• Flooded zones (brine/water) tend to be more conductive, while oil-rich zones tend to be more resistive, so the EM response changes as the front moves. 

1) Feasibility first (risk & cost control)

Before field deployment, ETI/KMS runs a 3D feasibility study constrained by:

• resistivity logs (including anisotropy when available),
• seismic horizons (reservoir boundaries),
• expected EOR variations (steam/water saturation + temperature),
• and measured field noise. 

In >50 % of evaluated cases, feasibility shows the anomaly is too small—so feasibility is the gate that prevents wasted surveys. 

2) Design the right measurement (not a generic EM survey)

The workflow emphasizes measuring both electric and magnetic fields because they respond differently:

• Magnetic fields tend to be more sensitive to conductive strata / water movement.
• Electric fields are crucial to resolve fluid changes inside the heavy-oil reservoir. 
• High frequenciess respond to the shallow part of the surface and low frequencies to the deeper strata.

3) Integrate surface + borehole measurements

For steam/CO2 flood monitoring, surface and borehole data must be integrated, including surface-to-borehole geometries and calibration to conventional logs (and anisotropy where possible). 

4) Improve focus and repeatability with array processing

To deal with noise and improve spatial focus, the workflow adds:

• differential measurements for highlighting specific volumes,
• array processing for noise rejection,
• and multi-frequency sensing for shallow, medium and deep targets. 

Three-dimensional modeling results show that conventional anomalies (~10–40 %) can be significantly improved with differential measurements (~40–200 % anomaly range), thus enhancing detectability and spatial resolution. 

In many mature EOR fields, open-hole logs are unavailable for repeat monitoring. ETI's through-casing resistivity logging progressed into field applications and can support:

• reservoir monitoring,
• bypassed reserve evaluation,
• environments where open-hole logs can’t be recorded

CSEM provides interwellbore-scale imaging, while cased-hole resistivity provides well-scale truth and change detection, together strengthening the monitoring loop.

1) Better sweep efficiency
Identify channeling versus uniform sweep and adjust injection rates/patterns earlier.

2) Faster diagnosis, fewer “guess” wells
Reduce uncertainty-driven infill drilling and workovers.

3) Quantify movement away from wells
CSEM extends visibility beyond the near-wellbore zone.

4) Lower monitoring cost vs repeating seismic
EM is faster and less expensive than seismic for this fluid-imaging task. 

5) Risk reduction
Pair EM fluid imaging with microseismic where seal integrity is a concern.