Evaluation Of Volcanic Reservoir Combining Well And Seismology

This paper comprehensively uses geological,well-logging,seismic and drilling data to study the volcanic rocks of the Carboniferous volcanic reservoir of well Che471 in the southern section of the Hongche fault zone with various geological,logging and geophysical methods.The characteristics of the volcanic mechanism,lithofacies,lithology and physical property in the study area are furtherly studied,and the favorable reservoirs of volcanic rocks are furtherly evaluated and predicted.It basically meets the research requirements and has important guiding significance for the deployment of favorable wells.The prediction of volcanic reservoirs in the study area is mainly based on seismic multi-attribute analysis and waveform indication inversion analysis technology.The single attribute analysis may be biased due to the existence of multiple solutions.The accuracy of reservoir prediction can be further improved by multi-attribute analysis such as coherence,amplitude and frequency.Waveform indication inversion technology combines logging with high resolution of vertical and seismic data with high resolution of horizontal to improve the accuracy of thin layer prediction.The main findings of this study are as follows:The top structure of the Carboniferous volcanic mechanism is characterized by a long axis anticline in the middle and north of the basin,which extends nearly north-south.The southern part of the overall structure is a northwest,southeast,and monoclinic structure with a nose-like morphology.The northern carboniferous volcanic mechanism is missing.Two fracture systems are mainly developed in the area: one is a reverse-fractured system with a near-south-north direction;the other is a near-east-trending normal fracture system,which cuts the north-south directional fault and forms four fault blocks and broken nose traps that have become favorable sites for oil and gas accumulation.Reservoirs in well Che471 section are mainly andesite,basalt and volcanic breccia.The pores of the reservoir are mainly dissolved corrosion pores,cracks,and pores.Andesite-basalt and volcanic breccia reservoirs are generally of low porosity and poor permeability,belonging to medium and ultra-low permeability reservoirs.The volcanic reservoir is affected by tectonic movement,and the whole volcanic reservoir is a dual medium reservoir of fracture-pore type.The volcanic rocks in well Che471 section can be divided into two phases from bottom to top.The first phase is dominated by the explosive facies,mainly develops volcanic breccia;the second phase is dominated by the overflowing facies,mainly developed basalt and andesite,and the tuffaceous conglomerate is developed in the middle.The volcanic lithofacies in the study area generally distributes in a nearly north-south direction.The volcanic structures in the north and west are not well developed and the volcanic sedimentary facies is mainly facies.The volcanic explosive facies and overflow facies pinch out northward and become sand and mudstone layers.The favorable reservoir in well Che471 section is distributed in 4 sections.Section I corresponds to the well Che471 stratum-fault block trap,section II corresponding to the well Che478 block trap,section III corresponding to the well Che476 block fault trap,section IV corresponding to the well Che541 block fault trap.Each trap has a high degree of closedness and a large trap area,which is conducive to oil and gas accumulation.