Abstract
The use of cumulative rock strength as a means of evaluating Polycrystalline Diamond Compact (PDC) drill bit performance has been successfully applied to the Cooper Basin, Australia by Santos Ltd. This has permitted a more engineered approach to PDC drill bit selection with a measurable improvement in overall performance.
As this field application consists of vertical wells, drilled in close proximity with similar parameters and operating conditions, it is possible to gain a high level of comparative data with quantified variables reduced to bit / cutter type and formation.
By cumulating the compressive strengths drilled above a determined limit, it is possible to compare bit runs and quantifiably evaluate existing and emerging bit /cutter types and thereby engineer future selections.
Field results have shown an average increase of 61% in the >25,000 psi Cumulative Overburden Compressive Strength formations drilled by the first PDC in the study area.
The initial success rate for the first PDC to get through the entire hard Namur/Hutton formations was 1 in 19 (5.3%). Utilization of the Cumulative Formation Compressive Strength (CFCS) methodology for bit selection increased the success rate to 75% for the last 4 full runs in the study, resulting in a reduction in rig time and associated costs.
