Research On Increasing Geology Signal Fidelity Processing Methods

Songliao basin is a sedimentary basin of large scale continental and thin interbed deposit, which has the characteristics of gentle formation, small structure magnitude, more faults and short breakaway distance, more oil-bearing formations and small single layer sandstone thickness. Majority of reservoir is lithologic oil reservoir under tectonic setting. Especially in midterm and later stage of Oilfield development, potential oil reservoir is lithologic oil reservoir, therefore lithologic exploration technology of oil reservoir description and prognostication are getting high attention. We need higher requirement for seismic data treating fidelity,which is our pursued target. Target of reflective seismic signal fidelity processing is by analysis processing of field seismic signal to eliminate seismic signal characteristic(amplitude , frequency etc.) change which is caused by non-geological factors, to make optimum matching of seismic signal's characteristic change and underground formation's geological change. Effective underground reflection horizon should be displayed on final achievement 's cross section good, at the same time, signal characteristic's relative relationship of point-point should be kept on the final achievement 's cross section. The research fully consider domestic and overseas development present-conditions, existing natural resources etc. to research prestack noise offset technology, secondary refraction attenuation technology, surface compatibility amplitude remedy technology, spherical diffusion & assimilation remedy technology etc. Main achievements are as follows: I. Main method of prestack noise offset technology research is to make analog noise and actual noise offset mutually according to noise's characteristics and by adopting noise offset technology. By test treatment of actual data, it was indicated that under prerequisite of smaller effective signal distortion the method eliminate fundamentally ground roll(surface wave), refraction wave and 50Hz industrial electric interference, after noise eliminated, shot gather record's waveshape is natural, signal to noise ratio gets improved greatly and doesn't produce false seismic event. II. Secondary refraction attenuation technology research: some linear interference that can't be eliminated by conventional methods often appeared in seismic record, which is called "Secondary Refraction", it will affect processing result's fidelity seriously. Secondary refraction attenuation technology's development has correctly analyzed secondary refraction's forming mechanism and dissemination law, put forward the conception—relative apparent velocity, has made the difficult problem that secondary refraction is hard to be eliminated solved completely, considered abnormal value's influence in linear interference, greatly improved the processing procedure fidelity. III. Surface compatibility amplitude remedy technology is an important link of signal fidelity processing. Trace equalization method which is adopted before were affected by random noise. When random is not uniform distribution on cross section, big error would be produced, may destroy true amplitude information. The research has put forward a new seismic signal energy statistical method –"relative energy method", can eliminate error that random noise create to amplitude computation. It's first time to consider error that seismic trace quality brings to amplitude statistics, to design seismic trace quality judgment method, according to given threshold value to accept or reject surface compatibility processing and stacked seismic trace, to lighten bad individual quality affect on stack seismic trace amplitude value. IV. Spherical diffusion & assimilation remedy technology when seismic wave spread underground, with extending of propagation distance, it's energy and apparent frequency lower gradually. Factors that cause seismic wave's decay are many such as spherical diffusion etc., therefore to eliminate earth...