Abstract:

The basin edge slope area of Changling fault depression in Songliao basin is mainly composed of intermediate-basic volcanic rocks. At present，there is a lack of in-depth understanding of the lithology, lithofacies distribution pattern， and high-quality reservoir stratum development law of the intermediate volcanic rocks in the basin edge slope area. By taking Longfengshan area in Changling fault depression as an example, the spatial distribution characteristics of volcanic edifice and volcanic facies were described by making a comprehensive use of well drilling, well logging, and seismic data,the volcanic facies model and eruption model were established, and the development law of the high-quality reservoir stratum was discussed. The research results indicate that the volcanic eruption center is located in the basin edge slope zone near the high place of the basin edge and distributed along the fault. The proximal facies belt of the volcanic edifice is featured with interlayers of effusive facies and explosive facies. The central facies belt of the volcanic edifice is mainly composed of pyroclastic flow of thick explosive facies. The pyroclastic flow is further advanced to the sub-concave center of the basin and then transformed into volcanic deposit facies. The volcanic facies is jointly controlled by  multi-stage Plinian eruptions, the transport and placement of volcanic eruptions, and other factors. High-quality volcanic rock reservoirs are dominated by volcanic tuff and vesicular andesite with strong dissolution, which are located in the medial facies belt of the volcanic edifice on the basin edge slope. The proximal facies belts with lava flow developed are the favorable development parts of the volcanic reservoir stratum in the area. The research has certain directive significance in the oil-gas exploration of intermediate-basic volcanic rocks in the slope belt of the basin margin of a fault depression basin.

Key words: Songliao basin, Changliang fault depression, steep slope, volcanic facies model, reservoir