The Sasino Shale.

The Sasino Formation is a shale-dominated sediment of mainly the Caracoc (Upper Ordovician) age, characterized by high lateral changes of its thickness and organic richness. The highest onshore net thickness of the formation is observed in the northern part of the Żarnowiec and Wejherowo concession blocks, where it reaches 36 m at maximum. Therefore it might be a shale oil/gas target by itself. In the most prospective zone, the thermal maturity of the Sasino Formation is an equivalent of oil to condensate window. 

In the central part of the Baltic Basin, the average TOC content of the Sasino Formation is relatively high, equal to 3-5.5 wt. %. It is characterized by a dominance of the II type of kerogen, favourable for shale gas and oil systems, however, due to locally elevated oxygen index a development kerogen type transitional between the II and the III is also observed. Due to coeval high RockEval S1+S2 and high TOC, the shale might be qualified as a good source rock. High oil saturation index is typical of the Sasino Formation in the northern part of the Żarnowiec and Wejherowo concession blocks, where it exceeds 150-200. This indicates high shale oil potential. 

The Sasino Formation is characterized by moderate to high brittleness. In the Żarnowiec and Wejherowo concession blocks its clay minerals content varies between 30 and 50 %, while quartz and carbonates content is 30-55 % and 5-10 %, respectively. 

In the Baltic Basin so far the majority of shale oil/gas well tests were performed for the Sasino Shale. The best daily IP flow, obtained from this shale reservoir, was 223 bbl of oil equivalent. In the Żarnowiec and Wejherowo concession blocks, the Sasino Shale reservoir is separated from the Jantar one by TOC-lean marls of thickness equal to 6-10 m only, therefore, the two formations have potential to be fractured together at one time.

Głębokość współczesnego zalegania niekonwencjonalnych, łupkowych skał górnego ordowiku i dolnego syluru w basenie bałtyckim (after Poprawa, 2019)
Position of the Sasino Shale in the stratigraphic section of the lower Paleozoic Baltic Basin