An Integrated Interdisciplinary Approach to Delivering Successful Infill Wells in a Mature Field

Jadestone Energy's main approach in maximizing recovery and extending mature field life is the integration of the various subsurface disciplines to improve understanding of the field development and production history. It is critical to capture the reservoir complexity and dynamic behavior to identify the remaining oil potential for future infill target opportunities. An integrated interdisciplinary study was conducted to capture the reservoir complexity and understand the dynamics of the rock-fluid interaction leading to identification of bypassed oil volumes. Challenges addressed are structural and well placement uncertainties, non-reservoir glauconite distribution, water sweep at local and reservoir scale. Further re-evaluation of 3D seismic and understanding of historical and current production performance supports the infill targets. Fast cycle times between geoscience and well designs criteria resulted in optimum well trajectories for drilling. Jadestone Energy acquired Stag field in 2017, located offshore Western Australia in the WA-15-L production license. Jadestone Energy has successfully drilled the first well, 49H in 2019 and replicated the success in 2022 by drilling two additional infill wells, 50H and 51H. 50H was strategically drilled perpendicular to existing wells to maximize reserves, resulting in severe anticollision provisions to drill across 10 wellbores within a narrow vertical window. This required careful planning and precise execution of the plan to stay in the sweet spot. 51H was considered as extreme- reach-drilling with the longest production section at shallow vertical depth. Drilling through low reservoir pressure, thin oil column was also impacted by risk of hydraulic fracture which required detailed geomechanical study. Both wells were drilled safely and achieved the desired outcomes. Reservoir mapping tools were utilized to assist in accurately placing and steering the wells within the reservoir's sweet spot. As a result, 50H inversion results affirmed water cone of 75m when crossing in the vicinity of active producer, matched model prediction for initial rates and water cut, while confirming thicker oil column at toe of the well. It proved the well placement uncertainties of the existing well as per prediction. 51H was drilled safely to target length despite suffering total losses before entering the reservoir. This too confirmed pre-drilled oil column thickness and unique structural prognosis. The success of an infill well drilling campaign was achieved through applying multi-disciplinary integrated solutions in a complex geological and production environment, coupled with overcoming challenging drilling operations through aggressive well planning and optimization. Successful application of deep resistivity reservoir mapping tools with geosteering was achieved for both wells.