Lower Cretaceous volcanic-sedimentary successions of the continental rift basin in the Songliao Basin, northeast China: Implication in high-quality reservoir prediction and hydrocarbon potential

Abstract

The high-quality reservoirs of volcanic-sedimentary successions in faulted lake basins are important enrichment sites for deep natural gas reservoirs. However, complex volcanic-sedimentary lithology and reservoir characteristics impede the efficient prediction of hydrocarbon in these successions. Therefore, we study the volcanic-sedimentary succession of the Huoshiling Formation (northern Dehui depression, Songliao Basin), focusing on the volcanic-sedimentary stratigraphic cycle (VSC), facies models and the distribution of high-quality reservoirs. Based on the log, core, casting thin-section, seismic and other data, fissure-type and central-type volcanic eruptions are identified. Three VSCs (1–3) are recognised, and six volcanic-sedimentary facies are determined based on lithological characteristics: effusive, explosive, volcanic conduit, volcanic-sedimentary transition, fan-delta and lacustrine. Based on the flow regimes and lithological associations, we develop three models: a fissure-central volcanic effusive model, an intermittent volcanic activity model and a fissure-central explosive model. Three types of pores occur in the volcanic-sedimentary reservoir space: primary pores, dissolution pores and micro-fractures. Lithology and dissolution are critical factors controlling reservoir porosity and connectivity. The distribution of high-quality reservoirs of volcanic-sedimentary successions can be effectively predicted using geostatistical seismic-inversion based on porosity constraints. High-quality reservoir characteristics, source rock and structural characteristics show that crystal debris and breccia-bearing tuff in VSC3 can form structural-lithologic, fault-block and self-generating and -storing hydrocarbon reservoirs. This study's results and methods of high-quality volcanic-sedimentary reservoirs can provide a reference for the efficient exploration and development of oil and gas in similar basins.