Schlumberger

Case Study: Underbalance Surge Technique in Perforated Zones Used to Control Sand Production

TRUST technique improves packing efficiency and increases production in high-permeability Far East formations

Challenge: Control sand production in four wells drilled in unconsolidated, highly permeable formations.

Solution: Use the TRUST transient rapid underbalanced surge technique to improve the packing efficiency of the perforations.

Result: Improved packing efficiency of the perforations and exceeded production expectations from these four wells.

Increased production method sought

Sand production from soft, unconsolidated, highly permeable formations can make perforating and production operations less efficient. The costs of sand control, separation of sand from produced fluids, damage to production hardware, and restricted production are some challenges operators face in such formations.

An operator in the Far East had been perforating a well with a modest underbalance of 300 to 500 psi prior to gravel packing and was sometimes required to resort to acid stimulation to achieve economical production. The operator sought a better way to achieve cleaner perforations, prevent sanding in the guns, and obtain a high volume of sand-free production.

TRUST technique selected to improve packing efficiency of perforations

The operator and Schlumberger engineers reviewed data from previous conventional perforating operations in determining how to complete the well to optimize gravel-pack and fracture pack operations. They decided to use the TRUST underbalanced surge technique.

With the TRUST technique, a long surge chamber between two IRDV intelligent remote dual valves was run in the TCP string. A fast memory gauge was run close to the perforating guns to collect 28,800 data points per second for further analysis. Then, the well was perforated, surged at high differential pressure to clean the perforations and minimize skin, and reverse circulated. Rig time was saved because all operations were completed in a single run.

HSD high shot density guns with PowerFlow slug-free big hole shaped charges minimized damage and debris in the weak sand formations. To prevent sanding in the guns, they were pulled from the zone after overbalanced perforating and before opening the lower IRDV to create the brief, sharp pressure drop to an underbalanced state across the perforations.

Efficiency of packing improved

Four wells were perforated, surged, and gravel packed using the TRUST technique. Some of the wells had multiple zones that were completed separately. The production rate from the wells was expected to reach 5,000 bbl/d.

Dynamically surging the perforations and then immediately prepacking significantly improved the packing efficiency of the perforations. Whereas industry guidelines dictate that the packing factor should be no lower than 24 lbm/ft, three of the wells had an initial packing factor over 27 lbm/ft and reached 38 lbm/ft after they were producing.


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