Schlumberger

Case Study: Dynamic Underbalance Perforating Technique Doubles Productivity Index for Sinopec

Deploying PURE system in fit-for-purpose string achieves negative skin factor with no wellbore instability in Tarim basin, West China

Challenge: Maximize single-well production from perforating while reducing gun shock and wellbore-instability risk.

Solution: Boost production by using PURE clean perforations system, for clean perforations, which removes perforating debris and crushed-zone damage from tunnels immediately after guns fire.

Result: Doubled productivity index (PI) compared with conventional underbalance techniques; eliminated wellbore-stability issues and downhole tool damage caused by shock.

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.

  PURE system Conventional Conventional
Choke, in [mm]
0.12 [3]
0.12 [3]
0.12 [3]
Oil rate, bbl/d
339
309
284
Wellhead Pressure,
psi [MPa]
6,759 [46.6]
6,005 [41.4]
6,033 [41.6]
Reservoir Pressure,
psi [MPa]
7,034 [48.5]
6,599 [45.5]
6,570 [45.3]
Drawdown Pressure,
psi [MPa]
268 [1.85]
590 [4.07]
538 [3.71]
PI, m3/d/MPa
25.03
10.34
10.46
Skin Factor
–2.39
0.66
13.2

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.


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"The test data proved the PURE system can dramatically improve production and has a great market for production-enhancement campaigns."
Sinopec engineer
Perforating project

Remove Perforation Debris & Crushed-Zone Damage

PURE Perforating System for Clean Perforations
The PURE system creates clean perforations by optimizing the dynamic underbalance that occurs after charge detonation. Visit PURE System page