Zonal Isolation

Effective zonal isolation is essential for ensuring optimal stimulated reservoir volume.

Learn more about how diagnostics address these common challenges
Plug Failures & Pipe Leakage | Cement Integrity & Rotating Casing

Plug Failures

Most operators acknowledge instances of plug failures, slips and leaks are common. According to analysis from the ProTechnics Global Technology Team though, 90% of proppant traced wells exhibit at least one instance of plug leak or plug failure resulting in under-stimulated stages or over-stimulated super fracs. The percentage also increases with the use of dissolvable plug technologies.

Missed Pay: a plug failure between stage 13 and 14 results in minimal treatment of stage 14 while the injected SPECTRASTIM™ proppant tracer (yellow) continues to treat the preceeding stage 13.
Excellent Containment: all stages treated as designed

One factor to consider with plug failures is pipe leakage due to setting plugs across loose or corroded casing. Though less common, pipe leakage does pose its own set of challenges and remains an important factor in ensuring proper zonal isolation. Compromised casing integrity can not only impair frac fluid placement but also create long-term production problems.

  • More common in horizontal wells
  • Typically occurs when there is a loose casing connection
  • Often in the build section
  • Impact of pipe leakage is magnified by poor cement integrity
Pipe Leakage: poor frac containment due to suspected leaking connection

Cement Integrity

Poor cement integrity can lead to sub-optimal stimulated reservoir volume and potential well control problems during production. When evaluating this critical component of zonal isolation, poor containment is often quickly attributed to plug failure when many times cement integrity could be to blame. It is important to understand the difference between plug failures and cement integrity.

Plug Leakage: plug in place but leaking, stage 16 treatment entering through stage 15 perfs
Poor Cement Isolation: unconstrained axial stage vectoring due to poor cement placement

One technique the industry is looking to for improved cement integrity is rotating casing while cementing. During a recent ProTechTalk, William Hunter with Ovintiv commented on his experience rotating casing and the impact on isolation and fracture initiation.

“Pipe rotation is the route we’ve gone. We’ve started drilling longer and longer laterals so we went to a higher torque casing connection anyways that allowed us to rotate.”… “As we are moving more and more towards trying to get a planar fracture at each cluster, having that good isolation there is very important and rotating our casing while cementing has been a big win for us.”

Along with better cement coverage, SPECTRASTIM™ proppant tracing confirms significantly improved stage containment on all 3 wells with rotation.

Source: William Hunter, Ovintiv – SPE Workshop: Well Completions for Unconventional Resource Development Optimization and Parent-Child Interaction

Effective zonal isolation from cement placement and plug placement is essential for ensuring optimal stimulated reservoir volume. Poor zonal isolation can result from non-uniform cement placement, poor cement bonding to formation or pipe, plug failures, or casing leakage. SPECTRASTIM™™ proppant tracer during frac treatments can help identify these zonal isolation problems.