Titre du document / Document title

Results of geostatistical porosity mapping in Western Drava Depression fields (Molve, Kalinovac, Stari Gradac)

Auteur(s) / Author(s)

MALVIC T. ⁽¹⁾ ;

Affiliation(s) du ou des auteurs / Author(s) Affiliation(s)

⁽¹⁾ INA-Industrija nafte, d.d., Oil & Gas Exploration and Production, Reservoir Engineering & Field Development, CROATIE

Résumé / Abstract

Porosity values of the gas and gas-condensate reservoirs of the western Drava depression (Molve, Kalinovac, Stari Gradac) are geostatistically analysed, in four hydrodynamically connected reservoir lithofacies. Lithofacies are (from the oldest to youngest): lithofacies IV of prePz-D age, lithofacies III of P+T₁ age, lithofacies II of T_2,3+J age and lithofacies I of M_1,2 age. Laterally, the lithofacies are very similar, with minor differences depending on the observed field. The deepest and the oldest lithofacies IV consists of different metamrophic and magmatic rock, mostly diaftorite and volcanites. The next lithofacies III (Clastites), of permotriassic age, includes metasandstone and quartzite, and less portions of dolomite, dolomitic breccia, slate, and at the northeast of Stari Gradac also volcanite. Lithofacies II (Dolomites) mostly consists of different dolomite and dolomitic breccia, shale, and sporadic intrusions of pyroclastite and diabase. Lithofacies I is named as: Limestone in the Molve field, Breccia in kalinovac, and Clastite in Stari Gradec. The age is Lower and Middle Miocene, I.e. Badenian. These sediments are represented in Molve and Kalinovac by calcareous clastite, calcitic matrix, and some conglomerates and sandstone. The youngest are biocalcarenite and biocalcrudite. In Stari Gradac, such sediments are represented by different breccia, conglomerates and coarse-grained sandstone. Geostatistical mapping included variogram analyses, estimations and simulations. Four average variogram model ranges are determined, one by each lithofacies: 5 807 x 4 921 ft (IV), 9 285 x 6 660 ft (III), 7 244 x 3 035 ft (II) and 7 520 x 3 773 ft (I). All are approximated with the spherical theoretical model. The most appropriate estimations technique was Ordinary Kriging. The most appropriate interpolations are achieved in lithofacies IV and I in the Molve field, and in lithofacies III and II in Kalinovac field. Results of stochastical sequential simulations are expressed as interval of minimum, mean, and maximum values for each lithofacies. New mean porosities by lithofacies and fields are calculated based on 100 stochastic realizations. P1 and P99 realizations and interpolated maps are the base for outlining promising areas in different lithofacies regarding higher porosity. Lithofacies III is the most promising regarding higher porosity values mapped by presented methods, and compared with solutions from previous studies. Such promising areas were outlined in Stari Gradac on the northwestern (Stg-1z, 2 wells), central (around Stg-1, 4, 5 and Bny-5 wells) and southeastern (Bny-1, 3, 7 wells) parts of the field. The area with higher porosity, in Kalinovac field, is outlined along the central fault zone, among Kal-2, 6 and 12 wells. The central blok in Molve field, bordered by margin faults is described as the most promising area.

Revue / Journal Title

Nafta   ISSN 0027-755X   CODEN NAFYA4 

Source / Source

2005, vol. 56, n^o12, pp. 465-476 [12 page(s) (article)] (9 ref.)

Langue / Language

Anglais
Revue : Anglais

Editeur / Publisher

Croatian National Committee of World Petroleum Congresses, Zagreb, CROATIE  (1950) (Revue)

Mots-clés anglais / English Keywords

Variogram ; Fault ; Interpolation ; Kriging ; Sandstone ; Limestone ; Shale ; Dolomite ; Condensates ; Porosity ; Geostatistics ;

Mots-clés français / French Keywords

Variogramme ; Faille ; Interpolation ; Krigeage ; Grès ; Calcaire ; Shale ; Dolomite ; Condensat ; Porosité ; Géostatistique ;

Mots-clés espagnols / Spanish Keywords

Quebrado ; Interpolación ; Kriging ; Gres ; Calcáreo ; Pizarra no metamórfica ; Dolomita ; Condensado ; Porosidad ; Geoestadística ;

Mots-clés d'auteur / Author Keywords

porosity ; kriging ; stochastic simulations ; Drava depression ;

Localisation / Location

INIST-CNRS, Cote INIST : 1337, 35400013500062.0020