51316-7537-Effect of Residual Stresses on Casing Sour Burst Pressure

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Product Number: 51316-7537-SG

ISBN: 7537 2016 CP

Author: Shashank Nawathe

Publication Date: 2016

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In recent years there has been an increase in the use of high strength materials for production casing in deep water applications. It has been observed that many of these deep water wells are characterized by HPHT (High Pressure / High Temperature) or XHPHT (extra high pressure and high temperature) and contain a small amount of H2S originating from either natural geological souring or reservoir souring caused by water injection. As such the casing in these wells needs to have not only high strength but also good SSC (sulfide stress cracking) resistance. Because the SSC resistance of the materials generally decreases with the increase of strength a fit for purpose design with consideration of all the effects such as H2S solubility and residual stress becomes a key to the success of HPHT or XHPHT projects.Large magnitudes of residual stresses are a by-product of manufacturing processes in high strength and low alloy steel casings and are generally tensile on the outer diameter and compressive on the inner diameter. The compressive state of stress on the inner surface exposed to the sour environment has the potential to delay propagation of crack-like defects and increase the casing sour burst pressure. Quantifying the magnitude and distribution of residual stresses across the casing wall and their impact on the crack tip stress intensity factor might be beneficial for a precise load and resistance factor design.This paper presents a study to assess the variability of manufacturing residual stresses on the sour burst pressure in a C110 production casing. Multiple techniques such as X-ray Diffraction Deep-hole-Drilling and Split ring have been employed to measure the through-thickness distribution of residual stresses. A numerical study has been presented to assess the effect of measured residual stresses on the sour burst pressure of the casing.