MIKROFACJE I DIAGENEZA UTWORÓW DOLOMITU GŁÓWNEGO (Ca2) W REJONIE BARIERY MIĘDZYCHODU (PÓŁWYSEP GROTOWA, POLSKA ZACHODNIA)

Abstract

MICROFACIES AND DIAGENESIS OF THE MAIN DOLOMITE (Ca2) STRATA IN THE MIĘDZYCHÓD BARRIER AREA (GROTÓW PENINSULA, WESTERN POLAND)Abstract. The Main Dolomite rocks found in the Międzychód area are associated with a fragment of a dolostone oolite barrier comprising the western part of the Grotów Peninsula. The sections from the Międzychód-4, Międzychód-5 and Międzychód-6 wells contain diverse microfacies types characteristic of deposition in differentiated subenvironments within the carbonate barrier zone. Diagenetic transformations and development of pore space occurred as multistage processes. They were associated with both the diagenetic-depositional zones (eodiagenesis) and the burial stage (mesodiagenesis). Some of them lowered the reservoir potential (compaction, cementation, neomorphism), whereas others significantly improved it (dissolution, fracturing). Dolomite and anhydrite cementation, halite, clay minerals and bitumen impregnation reduced the pore space filtration properties. In some places neomorphism affected primary structural-textural features of the rocks. Dissolution and fracturing significantly improved reservoir properties (porosity, permeability). Dissolution of unstable bioclasts and cores of carbonate grains resulted in formation of moldic porosity.