[First Hit]

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The Previous HitBauerNext Hit Field: Case Study of a High Productivity, Low Relief Oil Field


This presentation provides a case study of the exploration, appraisal, and development of the Previous HitBauerNext Hit Oil Field; its transformation from a small anticlinal prospect to what is now the largest Namur Sandstone oil pool on the western flank of the Patchawarra Trough in the Cooper Basin, South Australia. Low relief anticlinal closures with oil pooled within the Namur Sandstone reservoir is the primary play on the western flank of the Patchawarra Trough. The Previous HitBauerNext Hit prospect was first identified using 3D seismic data and mapped as an anticlinal closure with 9 meters of relief. The prospect was estimated to have a mean recoverable resource of 0.5 million barrels of oil prior to being drilled in 2011. The discovery well, however, intersected a 14 metre oil column, and as of January 2015 the field has 19 wells on production and an estimated ultimate recovery of 13 million barrels. Growth of recoverable resource estimates continued through appraisal and early development drilling, due to highside structural results and better than expected reservoir performance. Drilling at Previous HitBauerNext Hit has consistently demonstrated a ±5 metre depth uncertainty at the reservoir level. Critical drills to the north of Bauer-1 were higher than expected and extended the field, while wells to the south were lower, but increased mapped closure height. Variations of this magnitude have a dramatic impact on low relief structures, and can result in large uncertainties for recoverable resource estimates, field development planning, and commerciality. Static and dynamic modelling was undertaken during the early development phase, which focused studies toward characterisation of the Namur Sandstone reservoir. This work showed that understanding the subtle geological variations was key to obtaining a history matched reservoir model. Model results were most sensitive to facies distribution, permeability, and kv to kh ratio. High permeability reservoir combined with a strong aquifer displacing a low GOR, low viscosity, high API oil, a primary recovery of more than 75% is indicated. Well and core data obtained after the initial modelling studies confirm the primary parameters, with permeabilities of up to 13 Darcys recorded. The lessons learnt during the discovery and development of the Previous HitBauerTop Field may benefit the future exploration, appraisal and development of low relief, high productivity fields, and analogous prospects.