Optimised under-reamer string design for the wells in Hai Thach field, Nam Con Son basin
Abstract
According to the drilling programme approved for Hai Thach field, the drilling section which is below the 16" casing liner (14.85" internal diameter) will be carried out with two separate BHAs: drilling the 12.25" section by PDC bit to the section target, and using the under-reamer equipment to ream the wellbore diameter to 14.5" and 16.5" in order to run the 13.625” casing string. The paper presents the study to calculate the optimal design of the drilling string to ensure the under- reaming of the wellbore as designed as well as to minimise the running time of the drilling string, thereby improving the drillex and capex. Test operation of the design was run after it had proven to be effective in theory. The application of the optimised under-reamer string design in the wells of Hai Thach field has brought a feasible concept, opening up new applications in the future for similar well profiles and geological stratigraphy in Vietnam.
References
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