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碳酸盐岩油气藏储集空间以裂缝和溶洞为主,在地震剖面上主要表现为“串珠状”。为了研究溶洞成像规律,本文通过大量的数值模拟,分析溶洞的成像分辨率,探讨溶洞成像与上覆地层、信噪比(SNR)、覆盖次数、偏移速度和偏移方法之间的定量关系。研究认为:①无论是溶洞的纵向分辨率还是横向分辨率,均满足1/4波长调谐规律,可以将薄层机理转用至溶洞分辨率解释;②溶洞的存在会对上覆地层产生下拉效应,使溶洞在地震剖面上呈塌陷等“非串珠状”特征;③高覆盖和小道距(面元)可提高串珠能量,压制偏移附带的背景噪声;④叠前偏移能改善资料的SNR,提高成像精度,特别是低SNR资料;⑤偏移速度偏小,串珠边缘下拉,反之会上翘,速度偏大带来的成像质量变差的程度要大于速度偏小;⑥不同偏移方法对缝洞成像效果存在差异,对于低SNR资料,溶洞成像拟选取频率域或频波域方法。
Carbonatite reservoirs are dominated by fractures and karst reservoirs, and mainly behave as “beaded” in seismic profiles. In order to study the imaging rules of karst caves, this paper analyzes the imaging resolution of karst caves through a large number of numerical simulations, and discusses the quantitative relationship between karst caves and overlying strata, SNR, coverage, migration velocity and migration method . The results show that: ① Both the longitudinal resolution and lateral resolution of the cave satisfy the ¼ wavelength tuning rule, and the thin layer mechanism can be transferred to the interpretation of karst resolution. ② The existence of karst caveons will cause a pull-down effect on the overburden , So that the cave in the seismic profile was collapsed and other “non-beaded ” features; ③ high coverage and Trail (face yuan) can increase beaded energy, suppress the background noise accompanying migration; ④ prestack migration can improve the data Of the SNR, improve imaging accuracy, especially low SNR data; ⑤ bias speed is small, beaded edge pull-down, on the contrary will upturns, the speed is too large to bring the degree of deterioration of the image quality is greater than the speed of small; ⑥ different partial The migration method has different imaging effects on the fracture holes. For the low SNR data, the method of selecting the frequency or frequency domain for the cave imaging is proposed.