API RP 90:2006(2012) pdf download

API RP 90:2006(2012) pdf download.Annular Casing Pressure Management for Offshore Wells.
• Change the production rate and monitor the “A” annulus for pressure changes. Ii the pnxluction rate is increased, then the annular pressure should increase, Likewise, ii the production rate is decreased, then the annular pressure should decrease. The annular pressure should change and remain constant, If the annular pressure does not change as expected or does not remain constant after the change. then there may be SUP because of tubing-to-annulus colnmunication. lithe pressure changes as expected and remains constant, the pressure is thermal casing pressure. A decrease in production rate should result in a decrease in the “A annulus pressure and an increiLse in the flowing tubing pressure. lithe “A’ annulus pressure increases instead of decreasing. then there is significant communication between the production tubing and the “A” annuIns. If the “A” annulus first begins to decrease hut later begins to rise, then communication exists between the production string and the “A” annulus, hut the leak rate is possibly small.
An increase in the production rate should result in an increase in pressure in the “A” annulus and a decrease in the flowing tithing pressure. If the pressure in the “A” annulus decreases instead of increasing, then there is significant communication between the production string and the “A” annulus. If the “A” annulus pressure first begins to increase hut later begins to decline, theti communication exists between the production string and the “A” annulLis, hut the leak rate is possibly small.
• While producing at a constant production rate. increase the annular pressure by 10— 15 percent by injecting fluid through the umbilical line and monitor the “A” aniiulus. If the annular pressure decreases, then SUP caused by tuhing-to-annulus communication may exist. lithe annular pressure remains stable for 24 consecutive hours while maintaining a constant production rate, the pressure is most likely thennal. Injection of fluid through the umbilical is possible since fluid quality and hydrate formation can be controlled during the injection of fluids.
Alternatively, the operator may use predictive models alone or in combination with a limited shut-in time bleed-down test or other techniques to demonstrate that the pressure is thermally induced and not sustained. Except for bleeding the pressure, the other diagnostic test methods may not determine if an annulus has sustained pressure masked by a thermal component. In all cases, the pressure analysis method is to be documented in accordance with Section 9.
The following general principles apply to the various diagnostic tests:
• All annular pressure evaluation tests should be documented in accordance with Section 9.
• The tlowing tubing pressure (FTP) and shut-in tubing pressure (SITP) should be monitored and documented dunog the test. Should either the FTP or SITP not be observed during the test, then the most recently observed pressure should suffice.
• The production rate should be monitored and documented during the test.
• Any applied pressures should he monitored and documented during the test.
• The subsurface safety valve should be open during the test.
• Pressure should either be continuously recorded or recorded at a set time interval such as a minimum of every hour.
• Careful consideration should be given to the amount of fluid bled from an annulus.
• Consideration should also be given to flow assurance issues related to bleeding fluids through the annulus monitoring line.
• Establish when to stop the bleed-down part of the test,
• Immediately following the bleed-down test, the rate of build-up should he monitored and documented for a set period of time or until the pressure has stabilized.
• Both bleed-down and build-up pressure should be recorded.
• The operator may consider replacing any fluid bled off during the test with an appropriate fluid. Annulus fluid replacement should be considered when stabilized casing pressure levels are significantly below hydrostatic. Dedicated casing annulus umbilical lines, if they exist, could be used for this purpose. Items to consider when evaluating replacement of the fluids bled-off include hardware configuration, need for corrosion inhibitors, filtration, casing/tubing collapse and burst properties. differential across the packer, and thermal expansion of the re-injected fluids.