The Facies Of Late Mesozoic Volcanic Rock And Its Reservoir Significance In Xujiaweizi Area, In Songliao Basin

The exploration of the Late Mesozoic volcanic reservoir in Xujiaweizi Area in northern Songliao Basin will be one of the missions of Daqing Oil Company, Ltd. in the near future. The aim of this study is to subdivide the Late Mesozoic volcanic lithology phase and subfacies in Xujiaweizi Area, then to establish the relationship between volcanic phase and reservoir, so that some scientific evidence can be found to predict the volcanic reservoir.The main technical method is integrating geology analysis with geophysical analysis based on both volcanic outcrop and drilling data: first, subdividing the lithology phase and subfacies of volcanic reservoir based on abundant volcanic outcrops; second, establishing the geology models of volcanic phase and reservoirs; third, using the geology model to identify the lithology phases of the volcanic core; forth, establish the relationship between well logging phase and seismic phase of volcanic reservoirs; finally, predicting the storage space of the volcanic reservoir.Through this study, 6 new cognitions and conclusions are acquired: 1) 4 eruption circles and their eruption time limits are identified; 2) The formation of the volcanic rocks has closely correlation with the major faultings and 3 NNW volcanic trends are formed under the control of such major faults as Xuxi, Songxi and Yuxi Faults; 3) 5 volcanic phases and 15 subphases are recognized. For each volcanic phases and subphases, their geology meaning and reservoirs characteristics are established. 4) Volcanic phases model in deep Xujiaweizi Area is established; 5) The upper subphase of flood eruption phase and the hot detrital flow subphase of the explosive phase are proposed as the most favorable reservoir phase trends; 6)The seismic and well logging indications of every volcanic reservoir phases are established. The prediction of favorable volcanic reservoir with few drilling data is preliminary achieved in this study.