Abstract

To selectively stimulate a well with a complex completion in a naturally fractured carbonate reservoir in a mature field, the use of a self-degrading diverter deployed by rigless means through 1 1/2-in. coiled tubing (CT) was necessary in addition to an effective acidizing schedule using relative permeability modifiers (RPMs) as an additional diverter. The well was completed in combined 5-in. casing (slotted liner at the lower part and upper free casing) and two upper perforated intervals.

Initially, a nonreactive treatment was performed, pumping 500 bbl of solvent through a slotted liner section to evaluate the lower zone.

After this, the operator's program involved adding two new perforated intervals in the upper portion. Following this, the challenge was to effectively treat the upper intervals while isolating the lower zone.

After consultation, the service company recommended temporarily isolating the lower zone with a self-degrading diverting agent deployed with 1 1/2-in. CT and immediately stimulating the upper intervals using a gelled acid blend system and a RPM as a diverter pumped during the stimulation phase.

A noncommercial production rate was obtained with the nonreactive treatment after the evaluation of the lower section (75 m in slotted liner section).

With the temporary isolation of the lower zone using a self-degrading diverter deployed throughout 150 m in the 5-in. liner, a reactive stimulation was performed by means of bullheading and directed to the upper intervals. Previous to the stimulation treatment, the well did not produce. After treatment, the well produced in natural flow 852 B/D of oil with 3.8 % water cut through a 1.45-in. choke. The outcome was excellent productivity in a problem well with a complex completion in a naturally fractured carbonate reservoir.

This paper highlights various challenges encountered while stimulating complex completion wells and describes step-by-step procedures followed to achieve outstanding results. Additionally highlighted is how lessons learned can be applied during future treatments on candidate wells.

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