Research And Application Of The Seismic Wave Attenuation Parameter Extraction Method

Seismic wave attenuation parameter is to identify an important indicator of oil and gas reservoirs. Attenuation parameters on the extraction method of influencing factors, the variation under different conditions with the application conditions and results of the in-depth research and practice, to find the oil, gas reservoirs to identify and predict the most sensitive parameters. These methods and techniques of research results, of great significance and practical value, will improve the reliability of oil and gas reservoir prediction In this paper,Attenuation of seismic wave theory cited in the classical theory of acoustic attenuation that the wave propagation in the medium, because of particle vibration of the internal friction and heat conduction and wave energy loss, such loss is the wave attenuation, the absorption coefficient can be used that the absorption coefficient a (v, s, f) is the propagation speed, distance and frequency of function, suggesting that the absorption of many factors, uniqueness of solution is relatively poor. To this end, the classical theory of acoustic wave propagation in homogeneous medium assumed to spread, with a cycle or a loss to characterize the medium wavelength absorption attenuation characteristics. This is a cycle or a wavelength of depletion levels (a stress cycle of the energy consumedΔw for the great time and rock strain energy stored in the ratio of w) is defined as the quality factor on its frequency and the dissemination and propagation distance and propagation velocity has nothing to do, only and physical properties of the media itself, which reduces the understanding of multiple solutions.Apart from Q, and a lot other than the earthquake, the frequency attribute parameters and reservoir structure with different degrees of relevance. In this paper, absorbing the results of previous studies based on numerical simulations and the calculation of quantities of measured data analysis, to obtain wave absorbing the pulse transmission method (with the spectral ratio equivalent) and the parameters of seismic attribute analysis method in-depth study of these two methods of application conditions, factors and application of results. The theoretical study, the actual testing of rock samples and two 8 wells in the reservoir region attribute extraction scripts wave analysis, the bulk of research results obtained. Fruitful results of this integrated refining, come to understand the following points:(1) wave absorption coefficient and reservoir properties of rock samples or variation between the understanding of:Q values of rock samples saturated by water saturated air than a large, full oil and saturated rock sample Q values are almost equal, with Q values that are difficult to identify the size of oil and water.rock Q value decreases with temperature, the increase of pressure, and vice versa.Time-frequency properties in the seismic wave analysis, the frequency attenuation gradient of K, the high frequency band width of the low frequency band width ratioΔw , Q value and so the structure and containing fluid with the reservoir, reservoir effective thickness, porosity and change .(2) From 8 wells in the reservoir section of synthetic seismograms calculated wavelet analysis, recognized that:Three wells in Sichuan, the variation: the effective thickness of a large reservoir, porosity, high-capacity wells is small andΔw large value, K value is large.changes in the South China Sea five well pattern: the Q value is less than oil reservoir water level, the more oil content, Q value is smaller; Oil reservoirΔw is larger than the aquiferΔw , the more oil, the greaterΔw , the more water , the lessΔw .(3) Different methods for constant velocity assumption understanding of adaptation:Pulse transmission method: In the laboratory, using ultrasonic testing of small rock samples (high 50mm or100mm), possible closer homogeneous medium assumption. But in the actual calculation, we found that the pulse transmission method to obtain Q in the process, the standard aluminum sample and the rock and the amplitude ratio of the number of independent variables in some cases f is not a linear relationship between the test system or other factors that the testing process does not meet the assumption of homogeneous media. In seismic exploration, oil and gas reservoirs due to the thickness of thin layer, the resolution of seismic and oil and gas reservoirs is very low compared to single-layer thickness, could not receive a single reservoir top and bottom of the non-harmonic tone. In a sub-wave seismic reflection or extension of time, would correspond to a number of reservoir and non-reservoir section of interbedded strata. Therefore, seismic reservoir prediction in the spectral ratio is generally not used (with the pulse transmission method equivalent).Time-frequency feature parameters extraction method: Seismic waveform is the reflection corresponding to the reservoir of reservoir structure information integrated embodiment, when the reservoir of reservoir structure (including the fluid) change, the wave will change accordingly, and describe the characteristics of the waveform or its spectrum With the change of parameters will be. Therefore, the frequency parameters to find on the reservoir properties, particularly sensitive to changes in parameters of fluid is important. Also recognized that only a single wave parameters obtained more waves than the parameters obtained multiple solutions is strong, it must make use of well logging, drilling, development of a comprehensive interpretation of such information can reduce the multiple solutions.Forced vibration method: This approach requires a high condition, the majority in the theoretical reflection interface to meet their requirements, but the actual seismic data, or laboratory test data of rock samples are complex, it's difficult to meet the conditions, so use this method to find the Q value of instability.This had a lot of rock with the testing and logging and drilling, development of information, it proves the direct absorption of seismic wave attenuation parameter Q, K,Δw can be used for reservoir prediction, the most sensitive parameter is the K. It also shows the way forward on reservoir prediction is valid.