Schlumberger

First CO2 EOR Pilot in the Middle East

Pilot helps define steps in EOR planning, execution, and assessment of results

The injection of carbon dioxide (CO2) into oil reservoirs for enhanced oil recovery (EOR) has received considerable attention in recent years. As many fields undergoing waterflood approach the limit of recovery, 25-50% of the original oil is left behind. Based on experience with CO2 flooding worldwide, a considerable part of residual and trapped oil can be recovered with miscible CO2 injection under appropriate conditions. However, to determine the full economic potential of the process, field pilots were needed to identify risks and confirm performance.

Carbon dioxide EOR pilot

The first CO2 EOR pilot project in the Middle East was unique because the CO2 flood was implemented with the reservoir at original saturation. Progress of the CO2 flood was monitored through pulsed neutron logging (PNL). Several pulsed neutron surveys were recorded in the injector, observer, and producer wells, and provided essential measurements for saturation analysis.

Pulsed neutron logging characterization

Monitoring for CO2 in miscible flood using PNL can also present challenges. Since CO2 environments are yet uncharacterized, reliable conclusions require that measurements be immune to the borehole environment or that perturbation be minimal and easily corrected. The pilot project helped develop steps to address challenges and achieve the objectives of the monitoring exercise.

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Lessons Learned

  • Ensure the reservoir is at undisturbed saturation in the wellbore vicinity.
  • Develop a monitoring strategy to detect the arrival of flood front.
  • Deduce residual oil saturations after the flood based on observer well.
  • Mitigate effects of parasitic fluids in near-wellbore region(s) following suggested measures.
  • Optimize borehole and casing size, and completion design.
  • Measure flow profile on producer directly with production logging sensors.
  • Improve logging sensor technology to assess fraction of miscible versus free CO2 in formation.

CO2 EOR pilot

Schematic of map of the field showing the area currently under productionBorehole environment in the injector well.Measurement environment in the producer well.
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