Wpływ diagenezy i tektoniki na rozwój właściwości zbiornikowych dolomitów frańskich w centralnej części rowu lubelskiego
Abstract
Diagenetic and tectonic processes controlling reservoir properties of the Frasnian dolostones in the central part of the Lublin Graben (Eastern Poland).
S u m m a r y. Petrological studies of core samples, integrated with mesostructural analysis of cores, and coupled with results of seismic data interpretation allowed to interpret evolving reservoir properties of dolostones of the Frasnian Werbkowice Mb. These crystalline and partly vuggy rocks form main reservoir horizons of the Ciecierzyn and Mełgiew A gas fields in the central Lublin Graben. The optimum reservoir properties were attained following the main phase of regional dolomitization and accompanying CaCO3 dissolution. These processes occurred after renewed subsidence in Viséan and before main phase of the Variscan inversion in lateWestphalian. In Late Silesian, after the onset of hydrocarbon generation, porosity was partly filled by a dolomite cement. The most important agent of porosity destruction, however, was a precipitation of anhydrite cement preceding main phase of compressional deformations. The latter led to a localized development of open fracture systems which, however, were soon filled with various cements related to dissolution-reprecipitation processes. After compressional event, the stress regime evolved towards strike-slip and extensional, which created fractures allowing migration of hydrocarbons to newly formed structural traps. Several observed structures indicate negligible post-inversion deformations, thus facilitating preservation of earlier formed hydrocarbon accumulations. However, successive stages of secondary migration could have occurred during indefinite time under strike-slip and extensional regime recorded as a distinct set of mesostructures.
S u m m a r y. Petrological studies of core samples, integrated with mesostructural analysis of cores, and coupled with results of seismic data interpretation allowed to interpret evolving reservoir properties of dolostones of the Frasnian Werbkowice Mb. These crystalline and partly vuggy rocks form main reservoir horizons of the Ciecierzyn and Mełgiew A gas fields in the central Lublin Graben. The optimum reservoir properties were attained following the main phase of regional dolomitization and accompanying CaCO3 dissolution. These processes occurred after renewed subsidence in Viséan and before main phase of the Variscan inversion in lateWestphalian. In Late Silesian, after the onset of hydrocarbon generation, porosity was partly filled by a dolomite cement. The most important agent of porosity destruction, however, was a precipitation of anhydrite cement preceding main phase of compressional deformations. The latter led to a localized development of open fracture systems which, however, were soon filled with various cements related to dissolution-reprecipitation processes. After compressional event, the stress regime evolved towards strike-slip and extensional, which created fractures allowing migration of hydrocarbons to newly formed structural traps. Several observed structures indicate negligible post-inversion deformations, thus facilitating preservation of earlier formed hydrocarbon accumulations. However, successive stages of secondary migration could have occurred during indefinite time under strike-slip and extensional regime recorded as a distinct set of mesostructures.