Well Integrity Analysis to Assess SCP Inside Hig Temperature Gas Wells

Abstract Frequent cases of high temperature (HT) gas wells experiencing annulus pressure have driven the development and implementation of advanced modelling and analyses techniques to assess the severity of the sustained casing pressure (SCP), its impacts on to the wells' cement and casings. The potential root cause of this build-up is also identified and rationalized. Two case studies are presented here based on their individual nature of the SCP incident and severity, and the most effective mitigations have been proposed and successfully implemented to maintain continuous productions without any need for any additional costly well intervention activities. Real-time pressure and temperature data are heavily relied upon to provide data to assess the SCP issues affecting the wells. Based on the obtained data, the impact of the annulus pressure magnitude and frequency of the build-up are assessed against the casings' allowable material limits. Once the casing integrity is confirmed and mapped against the maximum pressure limits, the cyclic pressure ranges are evaluated to assess the casing fatigue capacity and to determine the pressure bleeding intervals. The cement integrity checks are carried out based on the obtained data to check the annulus pressure magnitude and if the casing-cement interface (or cement bond) are breached. This will also help streamline potential root causes for the pressure build-up and provide insights into any remedial measures which can be taken or if the in-operation mitigations are still an effective option. For the two HT gas wells being assessed, the root causes are identified with sound rationalisations provided by the real-time data coupled with the analyses which are carried out. The mitigation plan to bleed-out on weekly basis is also found to be effective and safe which maintains the casings' fatigue life throughout the wells' intended production life, whilst having adequate load resistance to prevent any structural failures. The introduction of advanced numerical modelling to evaluate annulus cement integrity during SCP events have proved to be crucial in determining the remaining effectiveness of the anulus cement, in addition to obtaining the extent of the cement damage / cracks from the prediction during the continuous pressure build-up and subsequent bleeding-out cycles which may occur as rapid as every week. This has proven to provide insights and confidence into safe continuous production without needing for costly interventions etc.