Sustained casing/annulus pressure

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Sustained casing/annulus pressure (SCP/SAP) could occur in the well at any time during its life cycle due to several factors, such as gas migration from a high-pressure subsurface formation through leaks or cement sheath cracks in the casing annulus. It could also be caused by casing or tubing corrosion, connection failures, leaks in downhole accessories or other well integrity failures.

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Problem:

In this case, our Customer had a well with a sustained casing/annulus pressure (SCP/SAP) of 65 psi in the B annulus. After bleeding the pressure off, it kept building up over again. This represented a major risk to the well.

Diagnosis:

TGT conducted a survey with its highly sensitive Spectral Leak Detection (SPEC-LD) service to identify the leak source. The SPEC-LD* is a combination of high-precision temperature logging and high-definition spectral noise logging. The survey was conducted in two stages: at 65-psi surface pressure in the B annulus and while bleeding it off.

Findings:

The logging identified a channel behind casing that allowed the gas pressure to build up at the surface. It also enabled our Customer to identify the gas source in the rock matrix.

Actions:

The Customer worked over the well – it was perforated with high-density perforating guns and cement was squeezed above the gas source zone, eliminating the SCP/SAP.
August, 2016