Research On Carbonate Seismic Rock Physics Modeling And Reservoirs Prediction

The main gas reservoirs of the Ordovician Majiagou Formation in the Daniudi area of the Ordos Basin are mainly carbonate rocks.This reservoir has the characteristics of special storage space,complex type and strong heterogeneity,And affected by the overlying coal seam,the seismic response characteristics are not clear,and there are certain difficulties in reservoir seismic prediction.To this end,this paper carries out reservoir rock physics research,builds a Cracks-Pores Effective Medium model and reservoir rock physics interpretation plate,and uses the viscous dispersion wave equation to simulate the propagation of seismic waves in fluid-containing media.It is preferable to identify sensitive parameters of fluids in the study area,and apply the matching tracking algorithm to eliminate the influence of coal seam shields,thereby improving the prediction accuracy of favorable reservoirs and oil and gas distribution characteristics.In order to support the seismic exploration of the tight carbonate reservoirs in the study area,a systematic experimental study on the seismic elastic properties of the reservoir rocks in the study area was carried out,in particular,the rock carbonate seismic rock physical change law and its influencing factors,microcosm The study of the influence of pore structure on its elastic characteristics(elastic wave velocity,velocity dispersion and attenuation)establishes an experimental relationship between seismic elastic characteristics and reservoir physical characteristics.Under the dry condition,the velocity ratio of the dolomite sample is close to 1.81,and that of the limestone is close to 1.88.The analysis shows that the rock pore system can be simplified into a double pore structure,and the rock reservoir space is mainly composed of pores with larger vertical and horizontal dimensions,while the fractures with smaller vertical and horizontal dimensions contribute less to the overall reservoir space,but the permeability of the rock is controlled by them.Considering the influence of pore structure and fluid characteristics on seismic wave dispersion and attenuation,a model of Cracks-Pores Effective Medium was established to analyze the influence of porous media with fractures and fluid saturation on rock elasticity and dispersion.The elastic properties and dispersion of rock with a few cracks or gas are obvious.Based on CPEM model,rock physical interpretation chart of variable fluid saturation and varying fracture porosity considering the effect of dispersion is constructed,and applied to the analysis and interpretation of well logging data of carbonate reservoir in Majiagou formation,daniu,and effective quantitative estimation of fracture porosity and gas bearing of reservoir rocks in the study area is made.At the same time,the information of velocity,density,porosity and mineral composition of vertical and horizontal wave from well logging data is used to invert the pore type of reservoir and effectively describe the pore structure characteristics of reservoir rock.Using viscous dispersive wave equation to simulate seismic wave propagation in the fluid medium,the simulation results show that the gas bearing area of the seismic energy with the increase of frequency attenuation fast,viscous,diffuse in the time-frequency domain characterized by low frequency attenuation is slow,high frequency attenuation characteristics of fast,petrophysical analysis results,some fluid sensitive parameters(Poisson's ratio,Lamada Rho,Miu Rho et al.).On this basis,this paper applies the matching tracking algorithm to eliminate the shielding effect of the strong reflection of coal seam on the effective signal in a working area of Daniudi.The constrained sparse pulse inversion is used to characterize the reservoir distribution and the wave equation parameter inversion method(AVO analysis and pre-stack inversion)is used to predict the gas-bearing characteristics of the reservoir.The logging data and inversion results of a working area in Daniudi indicate that the seismic fluid identification technology based on rock physics has achieved good practical application effect,and the reservoir prediction results are in good agreement with the existing gas-bearing test results.