基于波动方程正演对九龙山地区茅口组地震响应特征识别研究

九龙山构造位于四川盆地西北部旺苍县和苍溪县境内,该构造具有构造规模大、隆起幅度高、保存条件好、纵向上多产层、钻井显示丰富等特点。本文主要针对九龙山构造范围内下二叠统茅口组储层的地质模型和正演结果,明确储层发育位置,找到对应的地震相特征,并对储层进行分级评价。通过测井响应特征、储集空间、储层厚度、曲率等综合分析,用波动方程正演模拟预测下二叠统茅口组地震响应特征。正演结果表明茅口组孤立溶洞型储层的地球物理响应特征为同相轴串珠状上拉、振幅减弱;茅口组缝洞系统储层的地球物理响应特征为茅口组顶界同相轴"扭曲断续、下拉"。在此基础上总结了孤立溶洞和缝洞系统两种地震响应识别模式,为储层的预测提供了参考依据。

Identification of seismic response characteristics of the Maokou Formation in the Jiulongshan area, Sichuan Basin based on forward modeling of wave equation

Located in Wangcang County and Cangxi County, northwestern Sichuan Basin, the Jiulongshan structure is characterized by a large structure, high uplift, good preservation conditions, long-term vertical production and abundant borehole expressions. This work focuses on the geological model and forward modeling of the Lower Permian Maokou Formation reservoirs in the Jiulongshan structural area, clarifying the reservoir development location, finding the corresponding seismic facies characteristics, and grading the reservoirs. Based on logging response characteristics, reservoir space, reservoir thickness and curvature, the wave equation is used to predict the seismic response characteristics of the Lower Permian Maokou Formation. Forward modeling results show that the geophysical response characteristics of the isolated caverns in the Maokou Formation are ascending and beating in the same phase, and the amplitude is weakened. The geophysical response of the reservoirs in the Maokou Formation is the discontinue distortion and pull down of lineups in the top of the Maokou Formation. On this basis, two seismic response identification modes of isolated caverns and fracture-cavity systems are summarized, which provide a reference for reservoir prediction in the study area.