Reservoir Characteristics And Oil/Gas Relationship In The Es₃ Sedimentation Of The Eastern Depression Of The Liaohe Rift

The Es3(The middle-late Eocene) in the Eastern Depression is at a stage of rift and fracture development. The structure belt is narrow and the sedimentation occurred alternatively with volcanic action, with sandstone and igneous rock reticulated, showing complex and conspicuous petroleum geology conditions. The lack of systematic research on sedimentation and reservoir has restricted oil and gas exploration in this area. This paper applies the new theory and method of sedimentology, sequence stratigraphy, petrology, reservoir geology and petroleum geology to guide the study on the Es3 sedimentation and overall reservoir research. Sedimentation and reservoir characteristics and oil/gas relationship are studied as per regional feature; depositional pattern and igneous rock development mode are constructed; the distribution of favorable reservoir is presented; and exploration deployment suggestion is proposed.Structural evolution had controlled magmatic exhalation and sedimentary evolution, and then controlled reservoir development. The major sources of sediment in this area are the uplifts on two sides, showing characteristics of near source, multi-source and juxtaposed source. The occurrence of igneous body can change source direction.The study of sedimentary marker has established facies models of alluvial fan, fan delta, delta, fluvial and turbid flow, defined predominant sedimentary facies and reservoir development areas, and believed that the Es3low had developed alluvial fan - braided river-alluvial plain sedimentary system, Es3mid had developed alluvial fan - fan delta-lacustrine depositional system, Es3up North had developed alluvial fan braided river delta-lacustrine depositional system, and Es3up south had developed alluvial fan-river-delta-lacustrine depositional system, thus clearly defined the plane distribution of each sedimentary facies. The glutinite,turbidite, stream channel and point bar sand bodies are favorable hydrocarbon exploration area.Sandstone reservoir distribution and physical property were controlled by sedimentary facies, diagenesis and lithogenous phase, etc;reservoirs of clastic rock and igneous rock had developed alternatively, which can attenuate the diagenesis of the sandstone underlying igneous rock and enhance reservoir property; the sandstone reservoir is comprehensively evaluated as low porosity-low permeability reservoir. The Es3up reservoir is mainly in the medium diagenesis stage of A₁, dominated by solutional diagenetic phase, solutional and partial recementing diagenetic phase, induced porosity was developed, reservoir property is good, mostly belonging to Class?reservoir.The igneous rock reservoirs mainly include trachyte (Rehetai-Huangshatuo area), diabase (Jiazhangsi, Qinglongtai areas), andesite (Dapingfang area), basalt, volcanic breccia (Hongxing area) and tuff, etc. Igneous rock reservoir is less affected by depth of burial and will be essential target of mid-depth exploration. Except volcanogenic and marginal facies, all the explosive facies, overflow facies and subvolcanic facies are favorable reservoir zones. Igneous rock reservoirs are classified into Class I, II, III and IV based on comprehensive consideration of lithofacies, physical property, deliverability, fissures development degree and other factors by integrating the results of lithology, lithofacies, fissures, well logging reservoir and seismic reservoir prediction. The control factors of hydrocarbon accumulation in igneous rock reservoir mainly include oil/gas conduction conditions, fissures development degree, and favorable facies,etc .This paper has achieved new cognitions in respects of depositional pattern construction, the relationship of sedimentation and volcanic action, two-type reservoir development and oil/gas relationship research. The research findings are of certain application value to future oil and gas exploration.