Successful Re-entry in a Challenging Drilling Environment: A Case Study

Abstract

Yaqut -1 well (Afiband) is located in Safedkoh Block of Dewan Petroleum Pvt Ltd at about 20km WSW of Taunsa City, district D.G. Khan- Pakistan. Well was originally drilled in 1986. Well was drilled to 2020m, tested and was declared as Dry. Dewan Petroleum, on the basis of seismic data, Re-entered the existing borehole and deepen the same to explore the targets as Lower Cretaceous (Sand Bodies), Lower Cretaceous Sand and Jurassic Limestone. There were big challenges to face before making well usable for evaluation and testing purposes. These challenges included Installation of Wellhead, drilling of cement plugs and cement squeezing of 307m (Selective) perforations in total 792m zone against four different horizons, Drilling of 1356m of 6” hole, conducting wireline logs, running in 5” Liner and successfully cementing it against loss zones. Another challenge was of severe losses because of under-hydrostatic pore-pressure regime/ profile. Detailed evaluation of cement slurry designs of offset wells, where there was poor cementation history; a long debate was opened between well services companies. Discussion included nine possible options, and on the basis of SWOT Analysis one with “Ultra- Light” cement slurry was selected. This paper discusses in detail the strategy of Installing wellhead, Drilling cement plugs & squeezing-off long interval of perforations and their pressure test, along with strategy of overcoming drilling challenges, Centralization of Liner and landing the same successfully and discussion of different 5” Liner Cement Slurry design options. Furthermore it will show lab results, subsequent study results and will outline different steps used in carrying out the design, the execution and evaluation of the results of successful operations, which resulted in a restoration of high productivity.