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利用超声波观测方法在实验室内分别研究了砂岩露头岩样在不同孔隙流体压力和含气 (水 )饱和度条件下所引起的地震响应 ,由实验观测得出如下结论 :①纵横波速度、品质因子、主频均随孔隙压力从低到高而逐渐减小。②随含水饱和度的增加或含气饱和度的减小 ,纵波速度在低含水饱和度基本保持不变 ,而当含水饱和度达到一定程度时 ,纵波速度明显增大 ;而随含水饱和度的增加 ,横波速度略有降低或基本保持不变 ;③砂岩部分气水饱和时 ,纵波品质因子和主频最小 ;而横波品质因子在低含水饱和度时 ,随含水饱和度的增加 ,横波品质因子和主频降低较快 ,当含水饱和度达到一定值后 ,横波品质因子和主频基本保持不变。这些认识可以作为利用地震方法来检测异常高压带和含气层的标志 ;同时也指明了用地面地震资料来检测异常高压带和含气层时应该使用的参数和方法。
The seismic responses of sandstone outcrops under different pore fluid pressures and gas-bearing (water) saturation conditions were studied respectively in the laboratory by means of ultrasonic observation. The conclusions drawn from the experimental observations are as follows: (1) P-wave velocity, quality Factors, the main frequency with pore pressure from low to high gradually decreased. (2) With the increase of water saturation or the decrease of gas saturation, the P-wave velocity remains basically unchanged at low water-saturation, and when the water saturation reaches a certain level, the P-wave velocity increases obviously. With the increase of water saturation And the S-wave velocity decreases slightly or remains basically unchanged. (3) When the gas-water saturation of sandstone is saturated, the P-wave quality factor and the fundamental frequency are the least. When the S-wave quality factor is low, the S-wave quality factor And the main frequency decreases rapidly, when the water saturation reaches a certain value, the quality factor and the basic frequency of the wave remain basically unchanged. These insights can be used as markers for the detection of anomalous high-pressure zones and gas-bearing zones using seismic methods, as well as parameters and methods that should be used to detect abnormally high pressure zones and gas-bearing zones with surface seismic data.