Nafta, Vol. 60 No. 12, 2009.
Izlaganje sa skupa
Stochastical approach in deterministic calculation of geological risk - theory and example
Tomislav Malvić
; DSc, dipl. ing. geologije, INA-Naftaplin, Sektor za geologiju i upravljanje ležištima, savjetnik
Sažetak
Calculation of geological risk (or Probability Of Success; abbr. POS) of hydrocarbon discovery in existing or new play or prospect in the Drava depression has been done using well-known deterministical procedure. Such approach, with slightly modifications, can be used in almost all reservoir lithologies in any hydrocarbon basin or depression. This calculation, although already an old-fashion tool, represent reliable tool and it is why it is still applicable in many oil and gas companies or consulting firms.
Analysis is performed in the youngest part of reservoir (which encompasses four lithofacies) in the Stari Gradac-Barcs Nyugat field. It is represented by coarse-grained sediments of Badenian age. This field is selected regarding there are already done some estimations of existence of additional hydrocarbon reserves in the ‘subtle’ traps, but also numerous geostatistical analysis with porosity data taken from all reservoir’s lithofacies. Of course, the youngest and the shallowest lithofacies included the most such measurements, and also it is (together with the next, deeper lithofacies) reservoir’s part with the largest hydrocarbon reserves.
Deterministical approach in POS calculation had been improved in deterministical-stochastical, by using geostatistical porosity maps, where this variable is expressed through three possible realizations (minimal, median and maximal) for analysed Badenian lithofacies.
Total POS remained the equal as such value calculated only deterministically (POS=0.375). It is because average porosity in analysed Badenian clastics varying in narrow interval, and its selection from stochastical results did not have influence on estimation of probability of new hydrocarbon reserves existence. But, in deeper lithofacies, where lithology is more heterogeneous and/or more cataclised, variations in porosity are significantly higher. In such case, introducing of deterministical-stochastical approach could result in changes in POS values, depending on which stochastical realization had been selected as representative.
Ključne riječi
geological risk; determinism; stochastic; porosity; Pannonian basin
Hrčak ID:
46147
URI
Datum izdavanja:
31.12.2009.
Posjeta: 3.825 *