AVO Analysis And Fluid Identification In Su Lige Gas Field Reservoir

With the current development of exploration technology in complex structure areas, based on studying and understanding of the AVO technological background, development history, current situation and development trends, this paper carried out basic research of rock physics. Combined with the parameter model and the actual work area, it mainly researched inversion AVO attributes parameter from prestack data, further revealed variable characteristics of lithology and pore fluid.This paper first introduces the basis of rock physics including porosity water saturation and density、Elastic modulus、reservoir parameters on the elastic parameters Gassmann equation and the Biot model、mainly in the rock physics. as it has been difficulty to compute modulus of dry rock, the paper summarizes some methods: method of direct measure、Empirical formula method、Backstepping method. It was builded Rock physics model of the different porosity, clay content and water saturation, and analysis of affect the bulk modulus, shear modulus or the speed of seismic waves.the modeling results show that the clay content, porosity increasing will make the shear modulus and bulk modulus decrease. It was the complex influence of water saturation, different effects for fluid combinations is not the same. Water saturation affect the P-wave and shear wave velocity and the relationship is a regular. there were rules was of decreasing shear velocity with water saturation increasing, the rate of change was similar to a constant. But changes of the wave velocity with gas was large than oil, gas relative change was of95, while pores was full of oil-water, the relative change was only20or so from0to100%of the water saturation,. P wave speed is sensitive to the fluid change, when Degree of gas saturated was in0-20%, the relative change of P-wave speed reached80, and the water saturation increases, the P wave speed rapid increased after slow decreases, However the P wave speed monotonically increased in the case of oil.This paper described the detailed accurate AVO theory, approximation theory. For the AVO seismic data processing and interpretation and application of AVO attribute analysis of the actual working area, detailing the physical meaning of the approximate formula each item, has laid a solid theoretical foundation. The accuracy of approximate formula varies based on Zeoppritz AVO equations, and this had an important relationship rock parameters with the difference between the upper and lower interface. Difference of AVO reflection coefficients calculated by the approximate equations and Zeoppritz equation were little in0°～30°Then combined with actual data in Su lige gas field. In logging and rock physics on the basis of analysis, the fluid parameters are some intersection figure, through the analysis of these cross plot, gets some can be a very good distinguish fluid sensitive parameters. Through the forward modeling, studying the box of8reservoir in the seismic data AVO response, and application AVO inversion method obtained inversion poisson’s ratio variation, fluid sings, attribute parameters for integrated interpretation section, to the purpose of the reservoir prediction.