Volcanic edifices of Yingcheng Formation in Changling fault depression of Songliao Basin and their seismic identification

Volcanic edifices play an important role in controlling the spatial distribution of volcanic reservoirs.Taking the volcanic rocks of the Yingcheng Formation as an example, the types of volcanic formations, seismic attributes and reservoir characteristics are studied in detail using drill cores and logging and seismic data. A volcanic edifice model is established. On the basis of lithology and internal flow unit, the volcanic edifices can be divided into 4 types, including acidic lava volcanic edifices ( single flow units and composite flow units) ,rhyolitic lava debris volcanic edifices, and basaltic lava volcanic edifices. Among these types, the acidic lava volcanic edifices ( single flow unit) consist of a single lava flow unit, and the seismic profile is characterized by a hill-like blank reflection. Additionally, this type of edifice shows a contiguous petal-like pattern in the waveform classification chart. The acidic lava volcanic edifices (composite unit) consist of several acidic lava domes and plate-like lava flows, and the seismic section is a combination of parallel and hill-like reflections. This type shows noise and short-line clutter in the waveform classification diagram. The rhyolitic lava debris volcanic edifices have multiple layers of stacked volcanic debris. The seismic section features a draping continuous parallel reflection over a large area, and this type of edifice is characterized by a ripple pattern in the waveform classification diagram. The basaltic lava volcanic structural seismic section shows a large area of parallel reflectors.The waveform classification phase diagram shows a single and continuous distribution. The volcanic edifices with better physical properties have the following characteristics： the primary porosity belt is well developed,the units in the volcanic edifices are superimposed, and the volcanic structure is not integrated. Acidic composite flow unit volcanic reservoirs have the best physical properties, and the acidic single flow unit volcanic reservoirs are the worst. This study provided some reference for volcanic exploration and reservoir study in areas with few or no wells.