Analysis of Volcanic Reservoir Characteristics and Main Controlling Factors of Hydrocarbon Accumulation in the Yingcheng Formation of Block X, Xujiaweizi Fault Depression, Songliao Basin

The volcanic lithofacies in the Yingcheng Formation of Block X within the Xujiaweizi Fault Depression, Songliao Basin, exhibit significant complexity. Despite extensive research, incomplete understanding of their distribution patterns and hydrocarbon accumulation mechanisms remains a critical constraint on effective reservoir development. This study employs a comprehensive methodology integrating seismic reflection characteristics, time slices, attribute slices, and well calibration to identify volcanic bodies based on lithological contrasts between volcanic rocks and country rocks. Systematic investigations were conducted on the geological formation background, lithofacies distribution, and hydrocarbon accumulation characteristics. Results demonstrate that volcanic rocks in Member 1 of the Yingcheng Formation are well-developed, with large-scale volcanic cones in the eastern high platform zone and smaller yet densely distributed cones in the central-western regions, predominantly formed by central eruptions of acidic volcanic rocks. Vertically, three eruptive phases are identified: Phase I (early-stage) occurs only in the northeast with thin deposits, while Phases II and III (middle-late stages) are widely distributed with substantial thickness, representing favorable exploration targets. The hydrocarbon reservoirs are predominantly structural-lithological and fault-lithological types, with local accumulations controlled by multiple factors including tectonic setting, volcanic bodies, lithofacies, faults, and eruptive phases. Final hydrocarbon accumulation results from the interplay of these multifactorial controls.