Optimize perforation technique to safely increase production

Sinopec had one well in the Tarim basin of western China that was producing below expectations. Although the company attempted to remedy the situation by applying a conventional underbalance perforating technique, the well was still not producing a viable amount. Further stimulation techniques could improve production, but operating costs and wellbore-stability risks proved to be a challenge. Sinopec sought a high-performance perforating solution that would improve production without compromising wellbore stability or downhole tool integrity.

Build string to deliver productivity-enhancing clean perforations

Schlumberger proposed using the PURE system. Unlike conventional perforating systems that rely on a large static pressure differential between the wellbore and the formation to remove perforation debris and crushed-zone damage, the PURE system fully exploits the transient underbalance that occurs immediately after perforating. This creates a large dynamic underbalance that enables collecting the perforation debris in the gun chambers, minimizing skin and leaving a debris-free path for flow from the reservoir to the wellbore—maximizing production with clean tunnels.

The risk inherent to dynamic underbalance perforating lies mainly in gun shock. To mitigate this risk, Sinopec also chose to use Schlumberger perforating-shock planning software to design an optimal, fit-for-purpose downhole string. The software considers the maximum force from a perforation-induced pressure wave, the force applied to the packer, gun movement, and reservoir-stability details to design a perforating string that minimizes shock.

Double productivity index with no gun-shock damage

The results of the PURE system perforating in the underperforming well showed negative skin for the perforated interval, and postjob production data indicated a twofold PI increase compared with predicted rates of conventional techniques. Further, the operation was completed with zero issues of wellbore stability and downhole tool damage caused by gun shock because of the optimally designed downhole configuration and accurate estimation of shock.