A major operator has been drilling deep liquefied natural gas (LNG) wells for several years in central Oman. These wells are typically drilled vertically, featuring a complex geological sequence, that provides a significant challenge to bit performance.
Historically these wells have been drilled in 90 days with Tungsten Carbide Insert (TCI) bits on packed rotary assemblies down to the 9 5/8" casing shoe and Impregnated bits on turbine assemblies with occasional TCI runs in the 8 3/8" section.
A detailed study of the LNG wells focused on drilling performance in each of the three hole sizes in a typical well profile. The findings suggested that the introduction of new PDC technology was viable over much of the intervals and that significant savings in terms of time and cost could be achieved.
This paper reviews the findings of the study subsequent recommendations and the application of advanced PDC technology and stable PDC bit designs. The resulting improved performance is demonstrated by examples shown from two separate fields in central Oman where significant savings were achieved in terms of both rig time and cost per meter.
The collaboration between the Operator, rig contractor, bit vendor and other service companies was necessary to provide the platform for a successful operation.