Features and hydrocarbon potential of source rocks in the Hongdi 1 well, Hongmiaozi Basin, Liaoning province

The Hongmiaozi Basin is one of the newly-identified Mesozoic sedimentary basins in the southeastern segment of the periphery of Songliao Basin. The degree of basic oil and gas geology research in the Hongmiaozi Basin is extremely low. The source rock types, organic geochemical features and hydrocarbon generation potential in the basin are unknown, which constrains the exploration and development of oil and gas resources in the basin. Based on the new drilling results of well Hongdi 1, some core samples were collected and tested for organic matter abundance, type and maturity of dark mudstone. The source rocks in the study area are mainly composed of black mudstone and silty mudstone in the Xiahuapidianzi Formation, Lower Cretaceous. The dark mudstone has a cumulative thickness of 101.16 m, and the single thickest layer is 24.85 m, finding fifty layers with oil and gas shows. The experimental results showed that source rocks of the Xiahuapidianzi Formation in the Hongmiaozi Basin have a medium organic matter abundance. The types of organic matter are mainly Ⅱ₂-Ⅲ, partly Ⅱ₁ and Ⅰ. The vitrinite reflectance ranges from 1.31% to 1.84%, with an average of 1.53%, indicating for a high maturity stage. Scanning electron micro-scopy analysis revealed that the mineral composition of source rocks consisted of clay and brittle minerals with average contents of 58.4% and 41.4%, respectively. Microporosity developed between muddy crystal grains, which is conducive to the improvement of storage space and migration channels, and to facilitate late artificial fracturing. The study showed that source rocks in the Hongmiaozi Basin have some potential for hydrocarbon generation, and there is an urgent need for continuous and intensive research.