| Tahe Oil field reservoir has vertical "multi-layer reservoir" characteristic. Bottom-up, shows of oil and gas were well in some strata, such as the Ordovician. Silurian. Donghetang Formation of Devonian. Kalashayi Formation of Carboniferous. Asi member of Triassic, Shushan River Formation of Cretaceous. Both the form and causes of clastic rock reservoir are very complex and ambiguous. Also in the lateral clastic rock reservoir is strongly nonhomogeneous and the facies change fast. Therefore the present situation of exploration and evelopment display that the allocation of well drilling and the discovery of oil and gas reservoir are restricted largely. For the complexity and ambiguity of the seismic wave field characteristics and low prediction accuracy of clastic rock reservoir, one theory idea for the actual targeted reservoir identification and prediction is needed urgently.In this paper, the physical characteristics of clastic rock reservoir and seismic forward modeling of seismic geological model are studied systematically. Combining the geological model and seismic model organically, integrating thought of forward and inversion, the general relationship between the seismic wave field characteristics and reservoir geometry, physical parameters, fluid properties, hydrocarbon saturation are summarized. Then seismic identification model of typical clastic reservoir is established, that can provide theoretical basis for the identification, implementation and evaluation of low-amplitude structural traps, stratigraphic traps and other subtle reservoir traps.The paper include four parts:1) Summarizing geophysical characteristics of rocks and sedimentary facies, by analysising Tahe oil field clastic reservoir data such as drilling, logging, testing of core elastic parameters etc.; 2) Establishing a large of seismic geological models, which greatly approach the actual geological conditions and features, according to depositional model of clastic reservoir; 3) Carrying through nonhomogeneous medium wave equation finite difference forward modeling, whose parameters according to the field and observing system design; 4) Studying the general relationship between the characteristics of seismic wave field, seismic attributes and the type, fluid properties, hydrocarbon saturation of clastic reservoirs, and establishing identification model of different types of seismic reservoir.The main results and understandings are briefly introduced as follows:1) Through the forward modeling of typical academic seismic geological model, the seismic wave field characteristic and seismic resolution in different seismic waves of frequency is summarized:(1) As the thickness reduces, the reflected wave of thin sandstone top and bottom interface interfere mutually. When the thickness become 1/4 wavelength, reflection amplitude achieves maximum. Within 30 meters, the relationship between reflection amplitude and thickness appear linear approximately.(2) The seismic wave field characteristics of thin layer sandstone can be affected by many factors, such as the thickness, interbedded stacking style, relative position of sandstone and mudstone etc. When the total thickness of sandstone and mudstone is less than 1/4 wavelength, seismic reflection wave structure change little, but reflection amplitude vary with the thickness of sandstone.(3) The lateral varies of velocity or thickness of sand can lead to the rise or fall of seismic reflection phase axis, syncline and low amplitude structure may be formed on the seismic section. The vary amplitude increases with the increase of thickness and velocity of sandstone.(4) Seismic wave field characteristics of low-amplitude structural sandstone model relates with its porosity and fluid properties. As the velocity of sandstone reducing, the reflection amplitude of the first trough of seismic reflection phase axis decrease to null firstly, and then increase; the uplift amplitude of the first crest of seismic reflection phase axis reduces and tends to level gradually, the reflection strength reduces firstly, and then increase.2) By combining actual seismic profile and seismic forward modeling, summarizing seismic response characteristics of clastic reservoirs in Tahe oil field, which provide evidence development and application of seismic technology for reservoir prediction.(1) The seismic reflection characteristics of thin sandstone in Cretaceous are recognized regularly:1. the waveform structure is mainly composed by a trough, which's amplitude strength is relative with thickness, velocity, density, porosity of sandstone obviously; 2,sandstone can be predicted by high reflection amplitude and strength; 3, oil and gas reservoirs can be recognized by frequency characteristics, that reflection strength is high in low-frequency segment; 4, When the fluid properties change, seismic reflection characteristics(such as reflection amplitude, reflection polarity, waveform structure) of sandstone with large thickness change largely. While, seismic reflection characteristics of thin sandstone change little.(2) The seismic reflection characteristics of channel sandstone in Triassic are also recognized regularly:1 Channel sandstone appear lentoid shape, which is composed with positive-negative strong reflection phase axis, it differ from the surrounding rock.2. Channel sandstone can be predicted by high RMS amplitude, attenuation, instantaneous frequency and wave impedance characteristics; 3 On the time-frequency profile, due to the attenuation of sandstone including oil and gas, low-frequency region appears high reflection energy, while high-frequency region appears low reflection energy; 4, the reflection amplitude of sandstone including gas is stronger then that of sandstone including oil or water.
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