The Study Of Petro-physical Properties Pre-stack Seismic Inversion

Petrophysical parameters were much important to reservoir description,and play an important role in the comprehensive evaluation of reservoir.The common petrophysical parameters include reservoir porosity,shale content,fluid saturation,reservoir pressure,reservoir permeability and so on,so petrophysical parameters inversion based on seismic data has been a wide attention research topic at present.This paper core is ptrophysical parameters joint inversion.The relationship between petrophysical parameters and seismic attributes is fully studied based on rock physics and pre-stack seismic forward modeling,and then we propose a method of petrophysical parameters inversion based on elastic impedance.This paper mainly studies a joint inversion method of petrophysical parameters based on elastic impedance,which is in the framework of Bayesian Theory.In the condition of the stability of elastic impedance inversion,the method proposed in this paper comprehensively applies some various theories such as Bayesian theory,Monte Carlo simulation technology,statistical rock physical model,and expectation maximization algorithm.This method could be characterized primarily by four steps: firstly,establish the inversion objective function based on Bayesian theory framework;secondly,establish the prior distribution of reservoir petrophysical parameters under the guidance of well log information,and next establish an appropriate statistical rock physics model to express the relationship of elastic impedance and petrophysical parameters;Thirdly,applies Monte Carlo simulation technology to achieve the joint spatial distribution of elastic impedance and petrophysical parameters;The last,uses expectation maximization algorithm to find the petrophysical parameters corresponding to the position of the maximum value in the posterior probability distribution,which is the final inversion results.This method is in fully used of the stability of elastic impedance inversion,realizes the purpose of stable inversion,meanwhile,improve the inversion accuracy.However,the method is not an inversion of petrophysical parameters directly from seismic data,is an indirect inversion,it uses elastic impedance to link the seismic data and petrophysical parameters,so there is still existing the accumulative errors in the procedure of inversion.The feasibility and effectiveness of the method is verified by its model test and the test result is more ideal,and then we use it in the clastic rock reservoir and also obtained the satisfactory forecast result,which proved the method has practical value.