Geology/Seismic Amplitude maps
Sir. what is the role of total,average and maximum amplitude maps in reservoir. Why we donot use a single amplitude map for the work.
I also want to know how amplitude is effected by porosity,permeability, lithology and hydrocarbon. Thankyou
I can only give you a bit of insight. I am not a geophysicist and do not pretend to be. The variations of seismic amplitude you refer to are collectively called seismic attributes.
They are measurements of the subtle variations in the amplitude recorded at the geophone. Using calculations shown at the link below, one can extract additional information from the amplitude signal recorded.
The attributes fall into three classes, Instantaneous attributes, Wavelet Attributes and Geometrical attributes. The latter are tuned to provide specific information on bedding geometry, dipping surfaces, areas of similarity, shale indicator, and fault surfaces.
The Instantaneous attributes cover amplitudes whereas the Wavelet attrubutes deal with frequency, phase and polarity changes.
These last two contain what are referred to as direct hydrocarbon indicators. That is, certain attributes can divulge information about hydrocarbons in the pores of the lithologies through which the seismic energy passes due to subtle changes in the seismic signal as recorded in that attribute.
So mapping these variations and comparing them can provide information on where subtle shifts in the seismic amplitude occur across an area of lithology. These changes can represent an area of increased porosity, or an area containing gas, or liguid petroleum whosepresence will cause subtle changes in the seismic signal. A total measurement might mask these subtle changes, whereas the average or maximum might reveal them.
I like to compare the use of seismic attributes to the used of various mathmatical manipulations of spectral data we used to acquire from satellite sensors. We could extract a variety of information from the data that was not visible to the naked eye, by combining various ratios of the spectral bands and assigning colors to them. Areas of mineralization then became apparent.
Seismic attribute calculations do something similar by utilizing the amplitude data and extracting additional information.