Skały osadowe czerwonego spągowca w wierceniu Kutno 2 w warunkach postulowanego jurajskiego wydarzenia termicznego oraz wysokich nadciśnień – studium petrograficzne
Abstract
Rotliegend sedimentary rocks in theKutno 2 well under conditions of a postulated Jurassic thermal event and high overpressure – a petrographic study.
A b s t r a c t. Ahigh signifance of the Kutno 2 deep borehole is due to its location in the central zone of the Polish Basin where the Rotliegend complex has previously never been achieved by other drillholes and thus was not recognized and studied. Drillcore from the Rotligend of the Kutno 2 has been recently studied for its petrography and facies. The Rotligend in this zone is represented by fluvial and alluvial sediments. It is composed mainly of fine- to coarse-grained sandstones, with conglomerate interbeds. Diagenetic processes of the sediments have been dominated by mechanical and chemical compaction, as well as by transformation of the unstable mineral components. Fluid inclusion analysis for quartz and carbonates indicates that the diagenesis-associated temperature reached 120–180°C. The presence of haematite pseudomorphoses after framboidal pyrite indicates an extremely high palaeotemperature of approx. 500°C. It is related here to the Jurassic hydrothermal event. The recent very high reservoir pressure might be associated with high temperatures due to the aquathermal pressure mechanism.
A b s t r a c t. Ahigh signifance of the Kutno 2 deep borehole is due to its location in the central zone of the Polish Basin where the Rotliegend complex has previously never been achieved by other drillholes and thus was not recognized and studied. Drillcore from the Rotligend of the Kutno 2 has been recently studied for its petrography and facies. The Rotligend in this zone is represented by fluvial and alluvial sediments. It is composed mainly of fine- to coarse-grained sandstones, with conglomerate interbeds. Diagenetic processes of the sediments have been dominated by mechanical and chemical compaction, as well as by transformation of the unstable mineral components. Fluid inclusion analysis for quartz and carbonates indicates that the diagenesis-associated temperature reached 120–180°C. The presence of haematite pseudomorphoses after framboidal pyrite indicates an extremely high palaeotemperature of approx. 500°C. It is related here to the Jurassic hydrothermal event. The recent very high reservoir pressure might be associated with high temperatures due to the aquathermal pressure mechanism.