Prediction of sealed annular pressure between dual packers in HPHT deepwater wells

Abstract

High-pressure and high-temperature (HPHT) deepwater oil and gas wells are under the influence of high-temperature formation fluid after putting into production. The thermal expansion pressure of sealed annular fluids caused by the annulus temperature change has large effect on the safety of strings among dual packers. This study presented a casing-cement sheath-formation model which take into account the effect of the sealed annulus temperature and volume changes between dual packers, established a displacement function of the sealed annular fluid, the free tubing and the cemented casing that based on the thermo-elastic mechanics, analysed the influence factors of sealed annular pressure, including the expansion coefficient and elasticity modulus of annular fluid, the wall thickness of casing and tubing stings. An example of a HPHT deepwater gas well was analysed. The results show that the sealed annular pressure has a positive linear correlation with the annulus temperature difference, and annular pressure buildup with the increase of thermal expansion coefficient and elasticity modulus of the annulus fluid, decreases with the casing wall thickness. To prevent the potential risk associated with annular pressure, high-compressibility and thermal-insulated materials could be developed to control sealed annulus thermal expansion pressure.