Redefining Well Abandonment Strategy: Tipping the Scale Towards Greater Cost and Operational Efficiency Through a Novel Multi-Layer Steel Barriers Cement Bond Logging
Authors: Zulkipli Siti Najmi Farhan , Johare Dzulfadly , Dangfa David Nanlung , M Amin M Farid , Yang Shahril , A Razak M Zahin , Omar Intan Salwa 
Published: October 2022

Abstract
Abandoning a producer or injector well post production decline and pressure depletion after all intervention efforts to revive the well productivity have been exhausted is gaining momentum in recent years by most of major operators. Huge number of candidates to be abandoned fall under legacy wells category with incomplete drilling history and cement integrity records which warrant new logging run to be conducted for cement bond evaluation at the expense of additional cost and rig time. Conventional cement bond logging will demand additional cost due to tubulars cut and pull requirement to obtain conclusive log evaluation of cement integrity behind multiple casing layers. This paper will highlight a novel and first deployment of new cement evaluation logging technology by the company in multi-layer casings environment to obtain cement quality assessment behind each casing within a single logging run.
Rigorous technology seeking efforts are conducted to fill in the industry gaps for a reliable and cost effective solution for well abandonment with unknown cement barrier status behind multiple casing layers. Total of four emerging technologies are evaluated including the slim logging tool version considering various technical criteria on job execution, operating principles, log data quality assurance, technical support and ways to improve which lead to the pilot deployment in 2 wells during the well abandonment campaign. The new cement bond logging technology was run inside a 7 inch tubing with the objective to evaluate cement quality behind 9 5/8 inch and 13 3/8 inch casings. Post logging run, the tubing was cut and pulled to expose single casing layer where conventional ultrasonic cement bond logging will be run for comparison with the new tool technology outcomes.
Results indicate that the new logging tool deliverables conform to the conventional logging outcomes which highlights the intervals of good, moderate and poor cement bond condition with likelihood for channeling and flow behind casing event. This approach achieves a lower operational cost by eliminating the cut and pull technique for existing tubulars which is a mandatory requirement for any conventional cement bond logging. The first job trial had successfully recorded USD 0.95 million cost saving, eliminating 3 days of rig time and optimizing 6% of total operational cost. Best practices and quick operational guideline imperative for optimizing well abandonment campaign have been developed to set the high tone for cost and operational excellence.
In conclusion, the newly introduced cement logging technology capable of evaluating cement quality behind multiple steel layers had shown encouraging results to support a cost effective well integrity assurance. Technology and measurement will keep evolving with time to resolve current business challenges as well as serving a more advanced technical requirement in the future.