The TRUST transient rapid underbalance surge technique is a single-trip perforating and surge process used in unconsolidated sands. Specifically designed to achieve effective cased hole gravel-pack completions, the technique also provides efficient cleanup of the perforation tunnels by removing perforation debris and crushed sands behind casing.

At the heart of the TRUST system is a downhole atmospheric chamber with either a single-shot annulus-pressure-activated pipe tester valve (PTV) or the IRDV intelligent remote dual valve at the top. At the bottom is another IRDV dual valve, which is positioned above the gun string. Following guidelines derived from laboratory studies, specialists size the chamber volume to provide a set inflow per perforation.

High differential pressure localized around perforations causes formation fluid to surge into the wellbore. This flow helps push out loose fines from the tunnels, and then the fines settle to the bottom of the rathole. The surge chamber design is critical for success and must be carefully done to ensure effective cleanup without formation collapse.

The standard TRUST technique assembly consists of

• HSD high shot density perforating gun system
• retrievable packer
• lower IRDV valve
• surge chamber
• PTV or upper IRDV valve.

An eFire electronic firing head or a stand-alone fast gauge can be run to record the dynamic underbalance during the surge.