Advanced Perforation Technology for Enhanced Remedial and Casing Recovery Applications

Abstract The introduction of Perforate, Wash and Cement (PWC) techniques have delivered a step-change in annular cement remediation efficiency versus conventional methods. The development of Tubing-Conveyed Perforating (TCP) charges capable of perforating production casings without damaging the outer casing string further facilitated effective cement remediation between concentric casings in less than half the rig time typically taken by section milling. However, effective remediation via PWC techniques has been shown to be significantly challenged by relatively well-bonded annuli, since effective hydraulic communication cannot be reliably established. A novel TCP system has therefore been developed to enhance the capability of PWC technology to effectively remediate challenging annuli by ‘rubbelizing’ or ‘pulverizing’ the annular cement, thereby dramatically improving hydraulic connectivity and enabling circulation behind casing to be more effectively established, and so permitting annular cement remediation - and indeed potentially also casing recovery operations - where it may otherwise not have been possible. An extensive design and testing programme involving Computational Fluid Dynamics (CFD) analysis, full-scale gun System Integration Tests (SITs) and a full-scale proof-of-concept test in a test well were undertaken to develop an optimized TCP system capable of ‘rubbelizing’ annular cement between concentric casings, without damaging the outer casing such that effective remediation could be performed on well-bonded annular cement previously not suitable for PWC treatment. Furthermore, the application of the technology to two further use cases has also been explored: (1) the use of bismuth alloy as an alternative annular remediation solution, and (2) cemented casing recovery for slot recovery operations. Both of which have demonstrated significant promise, with the bismuth alloy application now successfully tested at full-scale, and the cemented casing recovery application now successfully tested by offshore field trial.