AN INTEGRATED PETROPHYSICAL STUDY OF THE THIN BEDS IN THE KUPARUK A SAND, KUPARUK RIVER FIELD, NORTH SLOPE, ALASKA
JERRY SOVICH, JIM KLEIN, NEIL GAYNOR, 1996. "AN INTEGRATED PETROPHYSICAL STUDY OF THE THIN BEDS IN THE KUPARUK A SAND, KUPARUK RIVER FIELD, NORTH SLOPE, ALASKA", Stratigraphic Analysis Utilizing Advanced Geophysical, Wireline and Borehole Technology for Petroleum Exploration and Production, Jory A. Pacht, Robert E. Sheriff, Bob F. Perkins
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The Kuparuk A sand reservoir has performed beyond the predictions of the original reservoir model. Water break-through has been late, original oil volumes appear to have been underestimated, and hydraulic fracture performance has exceeded expectations. The Kuparuk A sand was deposited in a nearshore, storm-dominated marine environment and is characterized by a high degree of lithologic heterogeneity. It has long been recognized from core that numerous thin clean sands (less than 0.5-1 ft thick) constitute a significant portion of the reservoir. The original petrophysical model was not able to resolve these features and computed “pay” intervals were restricted to thicker (greater than 1-2 ft thick) and less shaly sequences.
Recent work with micro-scanner resistivity data has shown that the thin sand beds can be resolved and the volume of sand computed. The electrical images can easily segregate thin sand and shale lithologies because of their resistivity contrast. This contrast allows the thinly-interbedded sand-shale sequences to be quantified using a net-to-gross curve. Results were calibrated using whole core to verify the image analysis. Integration of the micro-scanner resistivity data with a conventional clay volume algorithm led to a thin-bed model that was applied field-wide. This new thin-bed model is unique in that it has the ability to distinguish the thicker, water floodable pay sands, from the thinner clean beds which may have a lower recovery factor. The relationship between clay volume and net-to-gross determined from the electrical images furnishes a decreasing thin bed sand volume with increasing clay volume. Application of the updated thin bed model should impact the oil-in-place determination and lead to recognition of possible recompletion opportunities in the “A” sand. Additionally, such opportunities may be recognized in the overlying Kuparuk “B” interval where numerous hydrocarbon-bearing thin sand beds may be present.