Optimising the under-reamer string design for the well at Hai Thach field, Nam Con Son basin

Tóm tắt

According to the drilling program approved for Hai Thach field, the drilling section below the 16” casing liner (14.85” internal diameter) will be carried out by two separate BHAs: first drilling the 12.25” section by PDC bit to the section target, then under-reaming the wellbore to 14.5” and 16.5” diameter in order to run 13.625” casing string. Using two separate BHAs for reaming the wellbore certainly leads to a time increase in the run in hole (RIH) and pull out of the hole (POOH) of the drill-string and hence the associated costs such as rig and other related third party services. Therefore, it is necessary to study and calculate the optimal drill-string design to ensure the wellbore under-reaming as well as to minimise the drill-string running time, thereby improving the Drillex and Capex. The application of the optimised reamer string design in the wells of Hai Thach field has brought a feasible concept that can be applied for other wells having similar profiles and geological stratigraphy in Vietnam in the future.