Main controlling factors of volcanic reservoirs in the southern Songliao Basin

Volcanic reservoirs in the southern Songliao Basin are characterized by various types of accumulation space and complex structures,they are porous reservoirs composed of different media,including different pores,fractures and holes,and their physical properties vary greatly in space,with strong heterogeneity and changeful facies.The most important issue that needs to be solved in exploration is to make main controlling factors for the formation of volcanic reservoirs clear.Combined geological,logging and seismic data with current exploration results,we proposed a three-grade rule that controls the development of volcanic reservoirs in the southern Songliao Basin.①Types of the volcanic edifice control the development degree of reservoirs and a reservoir with the rhyolitic volcanic edifice has the best physical property.②A volcanic edifice-facies belt controls the distribution of reservoirs and a crater-near crater facies(CNCF) belt shows the best physical property.③Diagenesis and tectoclase jointly control the effectiveness of reservoirs,and the cryptoexplosion brecciation and weathering-leaching coupled with fractures bring about a better physical property.The different volcanic edifice has different pore spaces and physical properties of reservoirs.It is significance in predicting reservoirs and effectively exploiting gas accumulations to clearly recognize controlling factors for the development of volcanic reservoirs.