The Theory Of Field Data Acquistion On Thin Oil Reservoil Detection

The essence of the thin oil reservoir detection field data collection is how to improve the resolution of seismic exploration in the field data collection. Seismic Data Acquisition Instrument System is the key equipment in field seismic data acquisition,the quality of field seismic data acquisition depends on the equipment. The resolution of the Seismic exploration is still very low in the current, the fundamental reason there is not has a acquisition system which can satisfy the requirement of high resolution seismic survey.Dynamic range is a very important technical description of seismic exploration equipment,which reflect the ability and precision of the size of signal equipment records. High resolution seismic survey equipment can record dynamic range up to 120 dB of seismic signals. Whether the centralized digital seismograph at last century or the 24 telemetering seismograph, Their instantaneous dynamic range can only reach to 60 ~ 70dB, which is still far from the requirement of high resolution seismic survey.High resolution seismic survey require the seismograph can record seismic waves with high frequency and wide frequency band.As the high-frequency attenuation effection of the formation,cause the ground to receive the reflected wave with significantly lower frequencies and severe narrowing frequency bands. Therefore, in order to improve high-resolution of seismic exploration, we must compensate the attenuation of formation prior to the record of equipment.The thesis analyse attenuation effection of the formation in-depth in theoretically, derived four mathematical expressions of the plane-wave amplitude equations.As for seismic exploration,use P-wave speed as the plane-wave amplitude equation is very important, its brings great convenience to the theoretic calculations of the formational attenuation.This thesis gives the methods of making the formational attenuation model: Have known the seismic parameters T0, V0,βof a certain area, calculating seismic velocity Vav, Vav replaces the P-wave velocity to calculate formational attenuation; Furthermore it is known the seismic parameters T0,V0,βof an area, and the three parameters change with different depth, according different time of T0 to divide formations. According DIX formula to calculate different formations velocity vn, vn replaces P-wave velocity of the plane wave amplitude equation, calculating the formational attenuation for monolayer.According to the seismic parameters of the north of the Daqing Changyuan area, this thesis established 6 layers uniform thickness attenuation model, choice 200 Hz Ricker wavelet as the stimulate wavelet of seismic source, impressed by the shallow calculate the seismic reflection parameters in theoretical from shallow to deep(0.5s ~ 3.0s). The results showed : Time depth from 0.5 ~3.0s, the amplitude and frequency of reflected wave were much lower, Changes for amplitude was -95.14dB ~ 137.39dB, frequency was81Hz ~ 37Hz .According to the forward theoretical calculation, this thesis give the design of improve the system of seismic data acquisition equipment : Intelligent designing a preamplifier of intellective control to replace the traditional fixed-gain preamplifier. It is used to compensate the amplitude attenuation caused by the spherical posed; then design a SEF to compensate the amplitude attenuation and frequency step down caused by formational attenuation. According to established formational attenuation model ,estsblish the mathematical model of SEF transfer function, draw up its circuit diagram, used 2D wedge set geological model did forward modeling. Simulation results show that the design of SEF can effectively compensate the high-frequency attenuation of formation. The resolution of seismic exploration has been significantly improved, from the time depth of 0.5s ~3.0s, Resolution increase to the percentage of 82.6% - 75.9%.