Characteristics of diagenesis, isotopic relations and reservoir properties of the Middle Miocene sandstones in the Carpathian Foredeep (Poland and Ukraine)

Abstract

1 Pol ish Geo log i cal In sti tute -Na tional Re search In sti tute, Rakowiecka 4, 00-975 Warszawa, Po land Jarmo³owicz-Szulc, K., Koz³owska, A., Kuberska, M., 2015. Char ac ter is tics of diagenesis, iso to pic re la tions and res er voir prop er ties of the Mid dle Mio cene sand stones in the Carpathian Foredeep (Po land and Ukraine). Geo log i cal Quar terly, 59 (4): 750-761, doi: 10.7306/gq.1261The Up per Badenian and Sarmatian sand stones rec og nized from bore holes in south east ern Po land and west ern Ukraine are very fine to me dium-grained subarkosic and sublithic arenites and wackes. The de pos its un der went diagenesis well below 100°C, and their evo lu tion ary path ways of diagenetic and re lated res er voir prop er ties rep re sent eo-and mesodiagenesis. Eodiagenesis here com prised me chan i cal com pac tion, de vel op ment of chlorite, microcrystalline cal cite, py rite, sid er ite, kaolinite and quartz, and dis so lu tion of feld spar and mica grains. Mesodiagenesis in cluded quartz and K-feldspar overgrowths, albitisation, crystallisation of do lo mite and an ker ite and coarsely crys tal line cal cite, dis so lu tion of feld spar grains and car bon ate ce ment, and illite growth. The iso to pic data of d 18 O VPDB of car bon ate ce ments sug gest their crys tal li sation from porewater which is a mix ture of ma rine and me te oric wa ters. The d 13 C VPDB val ues sug gest der i va tion of car bon from mi cro bial methanogenesis of or ganic mat ter. The 87 Sr/ 86 Sr val ues in coarsely crys tal line cal cite are higher than those of Badenian sea wa ter. The ra dio genic stron tium may have been sup plied dur ing diagenesis by me te oric wa ters drain ing the con ti nen tal area. The Mid dle Mio cene sand stones show better fil tra tion abil i ties (good and very good) in the west ern part of the study area (Po land) than in the east. Pri mary inter gra nu lar po ros ity is more fre quent than sec ond ary intragranular and intercrystalline po ros i ties.The pri mary po ros ity was di min ished due to com pac tion and ce men ta tion from west to east. Some in crease in po ros ity was caused by dis so lu tion of de tri tal grains and by de cay of soft parts of or gan isms.