- Wells that exhibit a high producing fluid level, limited by equipment, and are not pumped off, even at high total fluid rates.
- A high water-oil ratio, or (WOR).
- An indication of good remaining oil column or mobile oil saturation. A well which has oil buildup behind the tubing which can be flushed out by circulating the well is an excellent candidate.
- The well should be relatively high on structure.
- The well should have had a relatively high initial production rate, and a good cumulative production history, demonstrating a significant amount of original oil in place.
Ideal Formation Characteristics
- Carbonates (Dolomites & Limestones)
- Highly fractured (Naturally)
- High permeability contrast within produced interval
- Bottom water drive
Required Information for Treatment Design
- Production data (Current)
- Completion data (Open Hole or Perforated)
- Lithology (Carbonate or Sandstone?) (Naturally fractured) (Degree of permeability variation) (Contrast)
- Logs and core analysis if available
- Water analysis (Produced water)
- Reservoir temperature
Preparation for Treatment
- Proper cleanup is critical for success. (Acidize, Swab, Clean out Wellbore)
- Pull rods and tubing
- Test tubing (Steam clean if necessary)
- Run and set tension packer +/-1 joint above interval to be treated
- Acid job to clean up iron sulfide, scale, etc. (This step is critical to assure polymer injectivity into water-bearing zone)
- Pre-treatment gel scan with mixing water to determine chemical formulation
- Injectivity Test - usually 2% Kcl water with premium biocide and surfactants
- Calibration of metering systems to deliver proper chemical formulation
- Start polymer injection-correlation of mixing systems
- Periodic sampling of mixture during treatment/quality control/determine gel times
- Treatment log-modified Hall plot-Monitor injection rate and pressure
- Moderate pressure buildup throughout treatment is desirable
- Excessive or rapid pressure response indicates plugging action (Reduce injection rates or terminate treatment)
- Oil post-flush with oil-soluble corrosion inhibitors and emulsion preventers
- Shut well in 3-5 days to assure maximum development of gel strength
Criteria to qualify a well for treatment includes: