Relationship between Volcanic Rocks and Hydrocarbon Accumulation during Dominant Period of Basin Formation in Liaohe Depression

Key words: 
• Liaohe depression /
• dominant period of basin formation /
• volcanic rocks /
• exploration field

Abstract: The dominant period of basin formation is defined as the period with the strongest tectonic movements, the largest extent of subsidence and the best development of source rocks. The sedimentary period of the 3rd member (Shasan, E2s3) and 4th member (Shasi, E2s4) of Shahejie Formation is the dominant period for basin formation. There were many episodes of volcanic movements during Cenozoic in Liaohe Depression, forming distribution of volcanic rocks with many series and types, which changes with the tectonic center and has the less strong activity in the earlier stages. The volcanic movements in the dominant period of Liaohe depression are abnormally strong and the appearances of volcanic rocks are frequent. The reservoirs which are altered by structural fractures and the corrosion and dissolution by formation water are favorable for oil and gas accumulation. The superposition in plane and the alternation in profile provide enough provision conditions of oil and gas sources for volcanic rock reservoirs. Furthermore, the volcanic rocks from dominant period of basin are of large thickness, widespread distribution and various traps and accumulation types, owning many advantages for oil and/or gas accumulation in many respects. The volcanic rock reservoirs for oil and/or gas in the areas of Huangshatuo and Oulituozi are typical representations among the above favorable reservoirs. The volcanic rocks from the dominant period of basin formation with favorable combination of oil and/or gas accumulation, enriching the content of oil and /or gas accumulation and the types of oil and /or gas exploration, are the important field for hydrocarbon discovery and exploration.