SUSTAINED CASING PRESSURE

Corrective or Preventive solution to SCP/SAP

Sustained casing/annulus pressure (SCP/SAP) may occur anytime during the life of a well. If the pressure builds up at a significant rate and exceeds the maximum allowable operating pressure, production or injection may have to be suspended and require a costly workover.
 
 
The symptoms itself can be mitigated by bleeding off the pressure at regular intervals if there is easy access to the wellhead. It is also common to fill the annulus with a heavier fluid in order to increase the hydrostatic pressure in the well. 
 
To cure the problem however, the pressure should be isolated from the wellhead by a gas tight plugging material close to the source. Sandaband may be a viable solution for such wells provided the existing annulus fluid can be displaced, either out into the formation or out of the well.

 

 


In this example, pressure builds up in the B-annulus, caused by an uncemented permeable zone or degraded/fractured cement at the shoe.

Bullheading heavy brine into this annulus may increase  hydrostatic downhole pressure and thereby reduce pressure at surface.

However, a liquid column will not prevent gas from bubbling up through the liquid column.

As it ascends, the gas will either expand (open shoe) or increase the pressure at the wellhead (closed shoe).
 

 

 

Here Sandaband is being pumped into the well and displaced by brine or seawater.

Bridging off at the restriction it will prevent gas from entering the annulus all together.

This can be done in any annulus provided there is injectivity and surface access.

The even better solution is to place Sandaband behind the casing during well construction.

A flexible reshaping material combined with a solid fundament at the shoe is the best assurance of a healthy well for the entire production period.

 



 
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