Geochemistry of Lithuanian Oils and Source Rocks: A Preliminary Assessment

Abstract

A series of oils and potential petroleum source‐rock samples has been analysed from exploration wells on‐and offshore Lithuania. Despite the limited amount of data, the results indicate the possible existence of partly‐exhausted source rocks within the Cambrian succession. Furthermore, possible source rocks are present within the Ordovician succession, and excellent source rocks occur within the Silurian in several wells. The source rocks are all present within a few hundred metres of stratigraphic succession, and the thermal maturity roughly follows the actual depth of burial, despite the fact that most of the subsidence and maturation took place in the latest Palaeozoic. The most important reservoir rocks are Middle Cambrian sandstones, but petroleum accumulations also occur in Ordovician limestones and Silurian reefal carbonates. Petroleum accumulations in Lithuania probably result from the pooling of oil derived from several sources, with the Lower Silurian (Llandoverian) shales being the most important single contributor.

Chapter 6 Phanerozoic palaeoenvironment and palaeolithofacies maps of the Arctic region

“…It was a large but rather shallow basin where quartz and glauconitic sand, graptolite ooze and detrital limestone with a total thickness of a few tens of metres (no more than 100 m) were deposited. In the Baltic republics, in Estonia and Lithuania, formations of black diktyonite schists were found (Kaljo et al 1988;Zdanavȋciuté & Bojesen-Koefoed 1997;Puura et al 1999;Modliński et al 2007;Raudsep 2008). Similar shallow marine conditions were in the Scandinavian part of the basin; however the sediments had another composition.…”

Sources of natural gases in Middle Cambrian reservoirs in Polish and Lithuanian Baltic Basin as determined by stable isotopes and hydrous pyrolysis of Lower Palaeozoic source rocks

“…Details of geology and petroleum occurrence in the Polish and Lithuanian parts of the Baltic Basin were published by Bogdanova et al (1997), Brangulis et al (1992Brangulis et al ( , 1993, Domżalski et al (2004), Karnkowski (1999), Kanev et al (1994), Karnkowski et al (2010), Kattai et al (1997), Modliński and Podhalańska (2010), Pokorski (2010), Poprawa et al (1997Poprawa et al ( , 2010, Schleicher et al (1998), Witkowski (1989), Zdanaviciute and Bojesen-Koefoed (1997), Lazauskiene (2004, 2007), and references therein.…”

“…The Baltic Basin (also called Peribaltic Syneclise) is a large, roughly NE-SW trending depression on NW margin of the Precambrian East European Craton formed by pericratonic subsidence during the Caledonian diastrofic-sedimentation cycle (Witkowski, 1989;Ulmishek, 1990;Brangulis et al, 1992;Zdanaviciute and Bojesen-Koefoed, 1997;Poprawa et al, 1999). The total area of the Baltic Basin is approximately 190,000 km 3 with about 60% covered by the Baltic Sea (Fig.…”

“…Several potential source rock horizons are present in the Lower Palaeozoic (Cambrian, Ordovician and Silurian) succession (Buchardt and Lewan, 1990;Zdanaviciute and Bojesen-Koefoed, 1997;Buchardt et al, 1998;Lazauskiene, 2004, 2007;Więcław et al, 2010a, b). The Upper Cambrian-Lower Ordovician (Tremadocian) strata contain the best source-rocks with low-organic sulphur, oil-prone type-II kerogen and are considered to be the most likely source of these offshore petroleum accumulations (Buchardt et al, 1998;Kosakowski et al, 2010;Więcław et al, 2010a, b;Wróbel and Kosakowski, 2010).…”

“…Petroleum exploration in Lithuania began in 1958. The first oil discovery was made in 1960 and oil exploitation was started in 1990 (Kattai et al, 1997;Zdanaviciute and Bojesen-Koefoed, 1997).…”