| Summary: | The oil and gas industry continues to demand more cost-effective well design and operations. Thus, this team successfully eliminated intermediate casing string from their design, achieving a 33% reduction in dry hole cost/meter, delivering wells, and producing oil 25% faster than before.Removing an intermediate casing string resulted in a long open hole (more than 2,000 mMD) which by default created new challenges which had to be dealt with and solved without compromising the targeted cost saving. The challenges can be summarized as follow: • Combining loss of circulation zone with unstable shale formations in one section. • PPFG uncertainties. • Bit selection and design optimization. • BHA selection and drive optimization. • Running wireline logging through a long open hole. • Running casing and having good quality cement. • Hole cleaning and displacement efficiency when changing mud systems. • Proper contingencies to meet the required completion strategy.Risk assessment, feasibility studies, workshops, and cooperation among all involved personnel have been conducted to ensure that this design optimization would result in a positive outcome.Since the first implementation in 2019, more than 17 wells have been successfully delivered and completed in Best in Class performance based on the latest update of Rushmore data tracking. The longest open hole section of 2,790 m measured depth (MD) with total depth (TD) of 3910 mMD has generated above 800 Kusd saving per well, thus setting new benchmarks for the field and opening up new opportunities for the future. All this ensures Process Safety and compliance with the Well Delivery process.This paper not only describes how a two-string design was successfully engineered and executed but also serves as a guide for selecting proper candidates for this design and an operational guide for two-section wells design to ensure that these challenging long open holes will be successfully drilled while minimizing risks.
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