True Single-Trip Wellbore Cleanout: Optimizations in Cemented Liner and Multi-Stage Frac Completions

Depending on the production requirements, the deep gas wells in the field were completed with cemented liner or multi-stage frac equipment. Following installation of lower completion, these wells historically required 3 to 4 wellbore cleanout runs prior to deployment of upper completion equipment. This paper will describe the optimizations done to convert all the cleanout runs, into a true single-trip job, reducing the total well construction by introducing groundbreaking technology and fit-for-purpose operations. The standard procedure wellbore cleanout involved 3 to 4 trips: Firstly, cement cleaning was done inside the 4-1/2″ liner, including drill-out of shoe-track, followed by scraping of 7″ liner for running test packer tool; then run and setting of packer to perform casing and top of liner pressure tests; next perform full cleanout of casings, pickle production casings and displacing well to brine, and finally polish 4-1/2″ liner tie-back receptacle to receive upper completion assembly in cemented applications. Detailed engineering analysis, risk assessment and market research were conducted to develop an optimized wellbore cleanout assembly, to perform single-trip jobs. The conventional cleanout package was upgraded with modified scrapers, magnets, and brushes, and combined with specialized high-pressure test packer and polish mill. Modification in equipment and procedures evolved following results and observations of several runs of the combined technology. The drilling and completion fluids were also re-engineered to ensure proper cleaning of casing and free-solids wellbore. The final results were an extreme success and single-trip wellbore cleanout became the new norm in the project. The innovate approach greatly contributed to reducing the number of runs to prepare the wellbore for upper completions. Operations have been conducted safely throughout its implementation and kept at low non-productive rate. In average, the reduction of total well time was 3.5 days with relatively marginal tool rental cost increment. This optimization was a breakthrough in the Middle East with major rig time savings and it will serve as a reference for other operators and service providers to achieve step changes in similar operations. The key elements of this initiative will be described in detail in the paper.