Abstract:

Volcanic reservoir is the exploration target in the Chagan sag. Establishing the volcanic reservoir-formating patterns is significant for choosing target and forecasting the distribution of volcanic reservoir. The major source rocks in the Chagan sag are composed of the second member of the Bayingebi Formation of Lower Cretaceous.There are many types of pore spaces in the volcanic rocks, including primary pores, primary fracture, structural fractures and dissolution pores brought out by later denudation and tectonism locally.The red mudstone in the second member of the Suhongtu Formation is the main cap rock, with the lithologic trap and the structural-lithologic composite trap which are made up of volcanic reservoirs existing. Studying the reservoirforming conditions and controlling factors, we proposed two patterns of volcanic reservoir-forming: the lithologic reservoir-forming pattern and the structural lithologic reservoir-forming pattern. The latter is the main type of structural lithologic reservoir-forming pattern.

Key words: volcanic reservoir, formation condition, reservoir-forming pattern, Chagan sag