DIAGENEZA A ROZWÓJ PRZESTRZENI POROWEJ W PIASKOWCACH PENSYLWANU POMORZA ZACHODNIEGO

Abstract

DIAGENESIS AND PORE SPACE EVOLUTION IN PENNSYLVANIAN SANDSTONES FROM WESTERN POMERANIA

Abstract. The Pennsylvanian sandstones of Western Pomerania are represented chiefly by quartz arenites and wackes. The main cement components are authigenic quartz, authigenic clay minerals (kaolinite, dickite and illite), carbonates (Mn-calcite, dolomite, ankerite, siderite), hematite and Fe oxides. Sulphates (anhydrite and barite) are common, but occur in small amounts. Locally, organic matter is observed. Diagenetic history of the Pennsylvanian sandstones from Western Pomerania includes eo- and mesodiagenesis. The estimated maximum temperature that affected the rocks during diagenesis could exceed 140°C. Porosity of the sandstones varies from 0 to about 20%. Primary porosity is predominant, whereas secondary porosity accounts for a small percentage. The major diagenetic processes, affecting petrophysical properties of the rocks, were compaction and cementation. Compaction resulted in primary porosity reduction by 37%, cementation by approximately 52% on average. Among the Pennsylvanian deposits, the best reservoir properties are observed in sandstones from the Dźwirzyno 3, Gorzysław 10 and Sarbinowo 1 boreholes.