engleski

Comparison and Benefits of Geostatistical Porosity Mapping in Western Drava Depression Reservoirs

Porosity behaviour at three gas-condensate fields in western part of Drava depression (Molve, Kalinovac, Stari Gradac) is geostatistically analysed, in four, hydrodynamic connected , reservoir lithofacies. Lithofacies are (from the oldest to the youngest): IV of prePz-D age ; III of P+T age ; II of T2, 3+J age ; I of M1, 2 age. Geostatistical mapping included variogram analyses, estimations and simulations. Four "average" variogram model ranges (honouring structure axes) are determined regarding lithofacies: 1770x1500 m (IV) ; 2208x925 m (III+II) ; 2292x1150 m (I). All are approximated with spherical theoretical model. The most appropriate estimations technique was Ordinary Kriging. The most appropriate interpolations are achieved in lithofacies IV+I at Molve field, and in lithofacies III+II at Kalinovac field. Results of stochastical sequential simulations are expressed as interval of minimum, mean and maximum values for each lithofacies separately. New mean porosities by lithofacies and fields are calculated from histogram based on 100 "equally-probable" realizations. P1 and P99 realizations are selected as base (together with interpolation maps) for observing promising porosity areas in different lithofacies. Such promising areas were outlined at all three fields. Stari Gradac - southern from wells Stg-1z, 2 and western from wells Stg-1, 4, 5 in lithofacies III (also, on Hungarian side in area of Bny-1, 3, 7 wells). Kalinovac - western from wells Kal-2, 6, 12, along main fault, especially in lithofacies III. Molve - central field block in lithofacies III.

porosity; reservoir characterisation; Kriging; stochastic simulation; Molve; Kalinovac; Stari Gradac

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