Seismic Imaging of High Impedance Mineral and Gas Hydrate Deposits

高阻抗矿物和天然气水合物矿床的地震成像

• 批准号: 249857-2012
• 负责人: Milkereit, Bernd
• 金额: $ 3.35万
• 依托单位: University of Toronto
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2015
• 资助国家: 加拿大
• 起止时间: 2015-01-01 至 2016-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=570745
• 关键词: Seismic; Imaging; Impedance; Mineral; Gas

Applying conventional seismic exploration techniques to image gas hydrate accumulations of deep mineral deposits poses a problem: seismic wave scattering caused by strong local contracts in physical rock properties. Massive sulfide exhibit variable compressional and shear wave velocities but density contrasts often exceed 50%. Gas Hydrate accumulations are characterized by high compressional and shear wave contrasts (up to 100%, highly variable attenuation (Q-factor) and no significant density contrasts. Modeling studies of such local high impedance (velocity-density product) contrasts require accurate 3D geological /petrophysical models consistent with all available borehole geophysical, geological and structural data. when strong local contracts in physical rock properties are present, seismic waves are scattered by the inhomogeneities. Two effects can be observed: the attenuation of the transmitted (direct) wave, the excitation of seismic coda (due to P-S wave conversion). Robust modeling capabilities of strong seismic impedance contrasts are important for a better understanding of wave propagation effects in small scale structures. 3D elastic/visco-elastic modeling of high impedance exploration targets (massive sulfide and gas hydrates) revealed that a local high impedance contrasts lead to strong and complex scattering responses, often dominated by converted shear waves. In addition, amplitude focusing caused by the shape of the deposit (scale factors) will lead to pronounced amplitude versus offset/azimuth trends. Thus seismic data acquisition geometries and source frequencies must be carefully selected in order to observe characteristic amplitude and phase variations. If observed, the scattering response may serve as a diagnostic tool to classify the composition of the seismic exploration target.The 3D earth/exploration models will be based on full waveform sonic and density logs, VSP, 2D/3D seismic data and extensive drill hole data from some of the largest massive sulfide and gas hydrate deposits on earth (The Red Dog Zn-Pb deposit in Alaska, Ni-Cu deposits at Thompson and Sudbury, gas hydrate accumulations in the Mackenzie Delta (NWT)).

将常规的地震勘探技术应用于图像深层矿物质沉积物的气体水合物积累提出了一个问题：地震波散射是由物理岩石中强的局部合同引起的。巨大的硫化物表现出可变的压缩和剪切波速度，但密度对比通常超过50％。气体水合物的积累的特征是高压和剪切波的对比度（高达100％，高度可变（Q-因子），无明显的密度对比度。 对这种局部高阻抗（速度密度产物）对比的建模研究需要准确的3D地质 /岩石物理模型，与所有可用的井眼地球物理，地质和结构数据一致。当存在物理岩石特性中的强大局部合同时，地震波会被不均匀性散布。可以观察到两个效果：传输（直接）波的衰减，地震尾co的激发（由于p-s波转化率）。强大的地震阻抗对比的强大建模能力对于更好地理解小规模结构中波传播效应至关重要。高阻抗勘探靶标（大量硫化物和气体水合物）的3D弹性/Visco弹性建模表明，局部高阻抗对比会导致强烈而复杂的散射响应，通常由转化后的剪切波支配。此外，由沉积物的形状（比例因子）引起的振幅聚焦将导致明显的幅度与偏移/方位角趋势。因此，必须仔细选择地震数据采集几何形状和源频率，以观察特征幅度和相位变化。 If observed, the scattering response may serve as a diagnostic tool to classify the composition of the seismic exploration target.The 3D earth/exploration models will be based on full waveform sonic and density logs, VSP, 2D/3D seismic data and extensive drill hole data from some of the largest massive sulfide and gas hydrate deposits on earth (The Red Dog Zn-Pb deposit in Alaska, Ni-Cu deposits at Thompson and萨德伯里（Sudbury），麦肯齐三角洲（NWT）中的气体水合物积累）。