地球物理技术在天然气水合物分布区预测中的应用

Applications of geophysical techniques to gas hydrate prediction

从天然气水合物发育区特有的构造沉积特征对各种地球物理响应的敏感性分析入手,研究地震属性分析、AVO分析、陡倾角地层反转速度场建立、伪井约束波阻抗反演等地球物理技术在天然气水合物预测中的应用及其效果。通过多信息联合分析与融合策略,优化集成有效地球物理技术,形成了一套可靠的预测技术方法。实际应用效果表明:反射强度、瞬时相位、层速度、相对波阻抗、绝对波阻抗、AVO截距剖面联合分析是识别天然气水合物底界似海底反射(BSR)界面的有效技术组合;综合应用原始地震剖面及相对波阻抗、绝对波阻抗、层速度等剖面的特征可提高天然气水合物识别的有效性;而瞬时频率、能量半衰期、层速度、AVO截距、AVO乘积、AVO流体因子等剖面特征的有效组合能更准确有效地识别BSR界面以下的游离气。

Starting with the analysis of geophysical responses of structural sedimentary characteristics of gas hydrate developed areas, this paper studies the applications of geophysical techniques and their effects in the prediction of gas hydrates, including seismic attribute analysis, AVO processing, inverted velocity field construction for steep formations, and pseudo-well constrained impedance inversion. By the tricks and programs of multi-information integration, effective schemes and methods are integrated into a set of reliable prediction means. The practical application shows that the combination of reflection strength, instantaneous phase, interval velocity, relative impedance, absolute impedance and AVO intercept is valid for identifying BSR （Bottom simulation reflectors） from lower boundary of gas hydrates. Integration of seismic section, relative and absolute impedance sections, and interval velocity section can improve the validity for gas hydrate determination. The combination of instantaneous frequency, energy half attenuation time, interval velocity, AVO intercept, AVO product, AVO fluid factor can locate the free gas under BSR accurately.