Discovery of the Jurassic strata of organic-rich source rocks under the Middle Proterozoic thrust-nappe in Niuyingzi depression, westhern Liaoning Province

This paper is the result of oil and gas exploration engineering.

Objective The target layer for oil and gas exploration in the Niuyingzi depression in western Liaoning Province has been Meso-Neoproterozoic. Due to tectonic uplift and other factors, the Jurassic Beipiao Formation, which is an important hydrocarbon exploration target widely exposed in other basins in western Liaoning, is not found on the surface of this depression.

Methods During the drilling of the LLD1 well, a set of thick dark mudstone layers were discovered beneath the Mesoproterozoic carbonates. Based on correlations of lithology and spore-pollen assemblages of the newly discovered mudstones with those from the Beipiao Formation in the Sanbaosikeng section of Beipiao Basin in western Liaoning Province.

Results The layers discovered were from the Beipiao Formation.

Conclusions Organic geochemical indexes indicate that the mudstone is of high organic matter abundance and high hydrocarbon generation potential. Hence, mudstones from Beipiao Formation in this area is a set of high-quality hydrocarbon source rock worthy of exploration. The discovery of thick dark organic-rich layers indicates that the Jurassic Beipiao Formation is a new target for oil and gas explorations in the Niuyingzi Depression. Moreover, this new discovery also provides important basic geological information for the study of tectonic evolution and hydrocarbon geological conditions in western Liaoning Province.