Sustained Casing Pressure (SCP) remains one of the challenges faced by operators.

This is especially difficult to repair successfully with cement without major workover operations.

Wellcem and Intelligent Energy Services Co. Ltd has been actively helping Saudi Aramco to solve Sustained Casing - Casing Annulus Pressure (CCA) problems, completing over 350 jobs with a success rate of 96.5%.

 

The Problem

Sustained Casing Pressure is usually defined as unintended pressure in a contained annulus resulting from the communication from pressurized form or gas resulting in pressure build up in the subject annulus that is measurable at the wellhead.

SCP rebuilding after having been bleed down and is not caused by wellbore temperature fluctuations is a clear sign that the well integrity has been compromised.

Read and download our Case Studies:

Causes of SCP

The leading causes usually are issues in the casing casing annulus or the tubing casing annulus. Causes for SCP In the Annular communication paths are generally the following:

A) Flow stream communication path

  • Tubing connection leak
    • A hole within the production tubing
    • Parting of the tubing string
    • Leak in gas lift mandrels, chemical injection mandrels or control lines
    • Packer seal leak
  • Seal, penetration, or connection leaks in the tree or wellhead


B) Annular communication paths:
    • Production casing hanger leak
    • Tubing hanger leak
  • Production casing string failure (Collapse, connection leak, hole due to corrosion, liner top failure)
  • Cement seal failure in an outer annulus combined with a casing leak in the production casing string
  • An uncemented section in an outer annulus combined with a casing leak in the production casing string


C) Potential flow paths into the outer annuli (e.g., B to C):
 
  • Cement seal failure
  • Exposed formation sections
  • Casing string leaks

Download Case Study - Sustained Casing Pressure in B-annulus

Common Cement Problems leading to SCP

Damage to cement from operational activities such as pressure testing, squeezing, or fracturing
  • Thermal cycling
  • Micro-annulus and channeling
  • Cracking/micro-fractures due to stress loading conditions
  • Weak cement bonding to the casing or formation
  • Lost circulation during cementing
  • Cement channeling due to ineffective mud displacement (Resulting in a conduit between different depths)


Remediation Methods

  • Workover – ultimate solution - expensive
  • Pressure Management – Not a permanent solution
  • Lubricate – in weighted brine or mud - Temporary
  • Circulation – of weighted brine or mud - Temporary
  • Annular Intervention
    • Internal casing patch
    • Cement injection*
    • Resin injection

* Note: Traditionally limited success


Wellcem Resin Solution - ThermaSet Resin

  • ThermaSet® is a thermosetting resin
  • Consistency as thin oil, density as seawater
  • Immiscible with water
  • Curing time can be accurately controlled
  • Density and viscosity can be tuned

The set product is:
  • Durable, it seals and bonds well
  • Proven to last in typical oil & gas well conditions
  • Flexible
  • Impermeable

 

SCP in the B-Annulus

Solution

  • A specific ThermaSet recipe was designed for this well.
  • 3,5 m3 of fluif was evacuatred from B-Annulus with the help of Nitrogen prior to pumping ThermaSet.
  • 3 m3, 1,9 SG ThermaSet pill was fed into the B-Annulus from surface with the help of a centrifugal pump.

Results

Successfully inflow tested the B-Annulus for 48 hpurs - No flow or pressure builkd-up on B-annulus

 

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Additonal reading - Published SPE papers

Download Case Study Sustain Casing pressure in B-annulus

 

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