The Research And Application Of Hydrocarbon Detection Based On Multi-parameter Inversion

The seismic inversion is always the key technology in the seismic exploration, especially with more and more complex geological conditions and the steep rise of the exploration cost. At present, the application of seismic technology is no longer confined to describing the structure; it has entered into the field of reservoir characterization; even to oil-bearing test, etc. In recent years, seismic oil and gas testing technique is playing a more and more important role in the process of oil field prospecting and development. Analysis of the oil and gas detection, parameter extraction and calibration, etc. these techniques have been developed rapidly.The seismic inversion aimed at predicting the impedance and other parameters about reservoir property from seismic data. These estimations are then used for characterizing reservoir,determine the lithology of rock and finding out the existence and the type of fluid contained in the rock porosity and thus used for the exploration and development of oil and gas resource. The conventional post-stack seismic inversion can only obtain the impedance and this has limited its capability of solving geology problems and it can't meet the demand of refined characterization of reservoir for the developing stage. The technology of pre-stack seismic inversion is a new technology that is emerging in geophysical exploration field.In some countries this technology has become an indispensable means of oil and gas reservoir prediction, and the hot spot of seismic attribute analysis and inversion study. The technology of pre-stack seismic inversion takes full advantage of abundant amplitude, frequency and other information in different angles pre-stack AVA seismic trace.It can obtain much more elastic parameters other than acoustic impedance,it can provide more way to characterizing reservoir and has enhanced the capability of describing complex reservoir and detection of fluid,which has important significance in reservoir prediction and reservoir characterization.Purpose of this paper is to obtain primary-shear wave velocity ratio, Poisson's ratio and other important elastic parameters for hydrocarbon detection,by using inversion results of different angles (near, medium angle) stack data. In the course of the study,taking into account a problem that the construction of low-frequency information in the inversion first to make the standardization of the well data itself, according to practical experience, a standardized method to consider impact of the depth is proposed. When carrying out pre-stack seismic inversion and pre-stack seismic attribute analysis, it requires accurate logging velocity curve of primary and shear wave. In the actual production, we often lack the S-wave velocity information,this paper studys currently several methods of shear wave velocity prediction and their basic principles for the problem of lack shear wave data.including: empirical formula, the model forward estimation method, constrained inversion method based on Biot-Gassmann equation, and make relevant analysis. In the application example,we predict S-wave velocity that pre-stack inversion demands,using constrained inversion method.The method takes into account the compaction effect, as calculated each depth point is only related to the current point,it has a physical mechanism to ensure and improves shear velocity prediction accuracy. Next, making a study of the corresponding for origin of the elastic impedance (EI) and the generalized elastic impedance (GEI).Generalized elastic impedance (GEI) overcomes the problem that velocity ratio of P-wave and S-wave maintains a constant from shallow to deep on elastic impedance (EI).With the incidence angle changes, it will not be much change in the dimension, so you do not need make normalization as same as elastic impedance (EI).On the inversion method, this paper studys colored inversion technology, it is a new inversion method that is developed on the basis of the colored filter technology.Colored inversion technique has the advantage that it does not require constraint of the initial model,and has higher resolution of inversion, less human factors during inversion. Using stack data of different angles pre-stack AVA angle gather, to obtain generalized elastic impedance (GEI) of different angles by colored inversion technology.Through joint calculation of generalized elastic impedance (GEI) of different angles,we can extract primary-shear wave velocity ratio, Poisson's ratio and the other important elastic parameters.Finally in an application example, using colored inversion technology makes generalized elastic impedance (GEI) inversion for angle gather data of the different angles on the same work area,then extract the primary-shear wave velocity ratio, Poisson's ratio and the other important elastic parameters by joint calculation,and using these elastic parameters make oil and gas detection in the region that has achieved good results, which confirmed that the method has the obvious advantage in complex reservoir description and fluid testing,and showed that hydrocarbon detection method of this multi-parameter inversion has broad application prospect.