First CO2 EOR Pilot in the Middle East

The reservoir in the first CO2 EOR pilot project is in a Cretaceous carbonate formation. The carbonate reservoir located in a previously unperturbed part of the field consisted of alternating porous and dense layers, which act as barriers or baffles. The average thickness of the reservoir is 130–150 ft and was divided into eight subzones based on porosity development. The average porosity was about 14%–17% and average permeability between 1 and 3 mD. However, evidence from core and logs indicated that the permeability within any given layer can vary by one order of magnitude.

Well Completions for CO2 Pilot

Located within an underdeveloped area, the mostly oil-bearing reservoir was at initial pressure above the bubblepoint and minimum miscibility pressure, and was not perturbed by any water or gas injection. To limit the CO2 injection volume requirements, the pilot consisted of three (3) wells drilled 35 m apart. The central observation well drilled in 1964 was put into production in 1994, and then squeezed off in 2009 to become an observer for the pilot. That same year, the injector was drilled with oil-based mud, and the producer was drilled with water-based mud.

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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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