During field development, as deeper coals are targeted for coal seam gas, operational performance is negatively impacted when drilling through the interburden and basement formations. A solution was sought to increase average rates of penetration (ROP) by extending bit life through vibration mitigation and improving drilling efficiency. The use of adaptive bit technology was seen as a novel way to address the drilling challenges encountered.
Based on a collaborative approach between the drilling team and the service company, two pilot wells were identified for the trial that were representative of the field, and could be benchmarked against a previous offset well so objective conclusions could be reached. Adaptive drill bit technology autonomously adjusts its depth of cut to changing lithology, mitigating stick-slip with no interaction from surface. This adjustment is achieved via a hydro-mechanical feedback system. As this would be the first time this technology would be run on an onshore application within Australia, a thorough analysis of the drilling system was conducted pre-well to ensure performance could be measured against a success case.
This paper discusses the basis for design leading up to runs on two wells, as well as capturing lessons learned as part of a continuous improvement cycle. Time and depth-based data were analyzed post run. Key performance indicators highlighted that the bits incorporating adaptive technology were able to drill the section at higher ROP with less weight on bit (WOB) than the offset well. This was demonstrated by a significant decrease in mechanical specific energy (MSE), resulting in improved performance and tool life. From an economic standpoint, drilling time savings in the range of 8 to 15 percent were observed.
An iterative approach will be taken to future designs, with subsequent bits incorporating a modified cutting structure to deliver further efficiencies in MSE. It is anticipated this could further extend bit life and reduce drilling cost by 10 percent.