Szczegóły publikacji
Opis bibliograficzny
The cap rocks sealing the reservoir in the Węglówka oil field, Sub-Silesian Unit, Polish Outer Carpathians – petrographical approach / Katarzyna GÓRNIAK // AAPG Bulletin ; ISSN 0149-1423. — 2019 — vol. 103 no. 10, s. 2369–2398. — Bibliogr. s. 2395–2398, Abstr.
Autor
Dane bibliometryczne
| ID BaDAP | 124988 |
|---|---|
| Data dodania do BaDAP | 2019-10-14 |
| DOI | 10.1306/01211917085 |
| Rok publikacji | 2019 |
| Typ publikacji | artykuł w czasopiśmie |
| Otwarty dostęp |  |
| Czasopismo/seria | AAPG Bulletin |
Abstract
The Węglówka oil field is located in the outer Carpathians. The outer Carpathians are a region where hydrocarbons were discovered and exploited at the end of the nineteenth century in several dozen oil fields, which are relatively small. The We? gl ówka oil field is one of the largest in this region. In the 150 yr or so of hydrocarbon exploration in the area, more than 1 million t (>1,237,000 tons [>8,841,000 bbl]) of oil have been produced. Hydrocarbons are concentrated in Lower Cretaceous sandstones (Grodziszcze and Lgota sandstones) that form an anticline sealed by Upper Cretaceous marls called the We? gl ówka marls. These cap rocks are up to 600 m (2000 ft) thick. Because of the thrustrelated exhumation, they were exposed at the surface and represent the youngest deposits in the region. The present work is focused on a detailed petrographic characterization of the We? gl ówka marls. This study allows petroleumgeologists to better understand the evolution of porosity in these cap rocks and can serve as a foundation for the prediction of their sealing properties. The marls appear as a succession of interbedded red and green varieties, which occur in up to 2-m (6-ft)-thick beds. These beds are nonarenaceous, soft, and bioturbated. Grain size corresponds to approximately 80% clay and less than 20% silt fractions. X-ray diffraction (XRD) reveals that the marls contain, on average, 54% clay, 28% calcite, 16% quartz, up to 3% feldspars and, in red marls, 3% hematite. The XRD patterns of clay are typical of mixedlayer illite-smectite ([I-S]; 40% illite in I-S). The clay structures are dioctahedral with similar octahedral Mg and relatively highFe3+ contents both in the red and green intervals. As revealed by standard petrography combined with high-resolution petrography performed through the use of a field emission scanning electron microscope, the marls have mudstone textures according to Dunham's (1962) classification and are mostly composed of coccoliths and clay with rare nanoquartz. This rock may be considered an impure chalk. Sealing properties of the We? gl owka marls are indicated by the specific surface area, porosity, pore size, and permeability, calculated using N2 gas adsorption, helium, and mercury porosimetry. The sealing potential is postulated to result from a combination of the following: (1) origin of components (i.e., deposition of minute calcareous bioclasts and volcanic material as a source for clay); (2) oxygenated sedimentary environment (as a result of the presence of oxygen in the sediments, burrowing caused the rocks to be homogenized); and (3) tectonic-induced clogging of pore space because of reorganization of clay flakes (the rocks were strongly tectonically deformed, which resulted in reduction of porosity in clay aggregates). © 2019 American Association of Petroleum Geologists. All rights reserved.
