Three-Stage Fracturing Treatments Save up to 12 Operating Days | Schlumberger
Case Study
Romania, Europe

Challenge: Limit upward fracture growth into gas cap and achieve effective oil well stimulation in Lebada field for maximum resource recovery at minimum cost.

Solution: Accomplish precise fracture placement with two proprietary Schlumberger technologies—StageFRAC multistage fracturing and completion services and ClearFRAC XT polymer-free frac fluid.

Results: Performed three-stage operation in a single sequence in two operating days, without rig or vessel standbys, resulting in a production rate 2.5 times greater than any other offset wells.

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Three-Stage Fracturing Treatments Save up to 12 Operating Days

Petrom uses StageFRAC and ClearFRAC XT technology to achieve production 2.5 times greater than offsets

Petrom S.A. is the operator of the Lebada field in the Black Sea offshore Costanta, Romania. Petrom’s objective was to stimulate a part of the reservoir still containing substantial oil reserves, obtaining optimal production through the placement of multiple fracture treatments while minimizing completion time and costs.

The target oil well intersects 50 to 60% dirty limestone laminated with streaks of different permeability. The well is close to the Cretaceous reservoir gas cap, with a trajectory perpendicular to a nearby fault. The operator was concerned about limiting fracture growth into the gas cap. Adding to the challenge, no specialized fracturing vessel was available in the Black Sea during the required time period.

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Modified supply boat using land-based fracturing equipment for Black Sea well stimulation for Petrom S.A.

Schlumberger proposed two technologies, StageFRAC multistage fracturing and completion services and ClearFRAC XT polymer-free frac fluid, to meet Petrom’s needs.

StageFRAC technology permits precise placement of multiple fractures in a single pumping treatment. Openhole packers run on conventional casing are used to segment the reservoir. Hydraulically activated sliding sleeves are located between each set of packers. Balls dropped from the surface during pumping open each sleeve, isolating previously fractured zones.

ClearFRAC XT stimulation

Petrom chose to use ClearFRAC XT extended-temperature fracturing fluid. This polymer- and solids-free viscoelastic fracturing fluid was less damaging than the polymer-based systems used previously in the area. ClearFRAC XT fluid significantly reduces fracture cleanup. It is insensitive to water quality and can be mixed with produced water. The fluid was formulated with seawater and mixed continuously during the operation. This flexibility enabled preparation of more than 1,100 m3 of fracturing fluid without the interruption of trips to port to refill the boat’s internal tanks, making it a very cost-efficient solution.

Log: Fracturing port placement versus formation lithology in a Petrom S.A. offshore well.
Fracturing port placement versus formation lithology in a Petrom S.A. offshore well.

Exceptional results

Fracturing treatments were pumped from a modified supply boat equipped with a dynamic positioning system. A jackup was used on site to support the operation.

Three separate zones of interest were selected to maximize resource recovery. Sonic Scanner acoustic scanning platform and FMI fullbore formation microimager logs were used to optimize the design.

Because all three fracturing operations were performed in a continuous pumping sequence, the entire completion process was executed in just 2 operating days—a savings of up to 12 days of operating time. The final result was effective reservoir drainage through multistage fracturing of openhole wellbores, which dramatically reduced completion times. After treatment, the well’s stabilized production rate was approximately 2.5 times greater than the area’s best offsets.

Based on the success of this project, Petrom is planning to run at least four additional jobs using StageFRAC and ClearFRAC XT technologies in the immediate future.

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“This was the first successful application in Europe of multistage fracturing in a Petrom well. The three-stage operation was performed in one on-the-fly sequence, providing significant savings of up to 12 days of operations and avoiding rig and vessel standby. Post-frac results exceeded expectations.”

- Viorel Ghita, Director of Asset 6, Petrom S.A.

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