First Field Application of a 27-M Extended Wireline Core Barrel to Reduce Nonproductive Rig Time in Adavale Basin, Eastern Australia

Abstract This paper presents the first field application of a 27-m wireline core barrel assembly and a new core bit design during a long-interval coring campaign at the onshore GA Enniskillen 1 deep stratigraphic borehole in Queensland, eastern Australia. The coring assembly was selected to deliver longer core runs, reducing the number of retrieval trips on wireline winch and in turn improving operational efficiency. The associated core bit was designed with the intent of maximizing rate of penetration (ROP), cutting and recovering high quality core samples, longevity over an extended coring interval, and the ability to handle the anticipated formations without catastrophic wear or damage. -The paper also covers considerations and operational choices deemed likely to prepare favorable hole conditions to core point. The coring program targeted a fully cored section of the Adavale Basin including the Boree Salt Member evaporitic rock sequence and allowed for the acquisition of detailed geological information above and below the Boree Salt Member, through formations with significant rock strength variability. Prior to coring, an 8.5-in polycrystalline diamond compact drill bit was run with the intent of minimizing borehole spiraling and maintaining verticality along with an eccentric wellbore conditioning tool in the same drilling bottomhole assembly, designed to reduce borehole rugosity and help ensure the coring assembly could be run to bottom without issues. At core point, the 8.5-in. × 3-in. core bit was run on a 27-m wireline core barrel BHA, including large bore mechanical jars. Coring parameters were managed by adjusting weight on bit, rotary speed, and flow rate to maintain stability, without compromising core recovery or quality. Offset data indicated rock strength ranged from 5 to 15 ksi and could increase significantly upon entry into the Boree Salt Member, with the potential presence of an overlying hard stringer. The coring system delivered a total of 975.47 m of core with 975.08 m recovered, resulting in overall recovery of 99.96% from 53 coring runs. A weighted average ROP of 4.89 m/hr was achieved, demonstrating consistent performance for a first application in the field. Approximately 10 m of anhydrite-rich Boree Salt Member was successfully cored in a single 27-m coring run with excellent recovery. This work provides field evidence of the successful application of longer wireline core barrel assemblies and useful information on non-planar shaped cutter performance over long coring intervals, across highly variable formation strengths. The results contribute new insight to reducing rig non-productive time and operational practices for achieving high recovery for long core wireline coring applications at significant depths.