Characteristics of volcanic reservoir of Yingcheng Formation in east Changling Fault Depression, Songliao Basin

Explorations of volcanic reservoir have achieved great success in the east of the Changling Fault Depression of the Songliao Basin in the past few years. Gas is found in the Yingcheng Formation in many wells. Volcanic reservoir is the key for natural gas accumulation. Based on core, logging and testing data, volcanic reservoir was analyzed from origin and evaluated. Due to low porosity and permeability, pores and fractures are well connected in volcanic rock, providing relatively good condition for accumulation. Especially in rhyolite and tuff, there exist multiple types of pores and fractures, including both primary ones generated during diagenetic stage and secondary ones transformed by later slacking. Reservoir parameters are closely related to rock density, rather than burial depth. Different volcanic facies have different reservoir condition due to different composition. The overflow and outbreak phases are favorable for reservoir formation. Besides, weather-worn may influence reservoir formation. Unconformities are also beneficial for reservoir formation.