顺北走滑断裂-断溶体物理模拟及地震响应特征分析

Physical modeling and analysis of the characteristics of the seismic response of strike-slip faults and the associated fracture-dissolution reservoirs in the Shunbei area

塔里木盆地顺北地区高角度走滑断裂对岩溶缝洞储集体的发育起着决定性的作用。为了明确断裂的地震响应特征,针对走滑断裂的宽度、非均质程度、横向可分辨能力、断裂样式及溶洞发育形式分别进行了物理模型的构建及实验地震数据的采集分析。结果表明,走滑断裂在地震剖面上的杂乱反射能量异常特征是断裂带宽度及破碎程度的综合效应;断裂横向分辨能力与上覆地层无密切关系,主要受子波等因素影响,但如果上覆地层吸收衰减严重,则会导致频带变窄,地震波长变长,从而降低横向分辨能力;断裂带内部发育的溶洞无明显“串珠”特征,大规模溶洞及反射界面处发育的溶洞能产生“串珠”特征,但仍难与断裂产生的杂乱反射进行明显区分。通过模型响应结果与实际地震资料的对比,形成了关于顺北地区3种典型断裂地震响应特征的认识,即断裂弱反射、断裂强反射、断裂杂乱反射+“串珠”,为该地区实际断裂的识别提供了有效参考,对类似地区走滑断裂及相关断溶体的检测具有借鉴意义。

High-angle strike-slip faults in the Shunbei region of Tarim Basin play a decisive role in the development of karst fracture-dissolution reservoirs.In order to clarify the characteristics of the seismic response in this area,physical models were set up and experimental seismic data were acquired,so as to characterize the different width,heterogeneity,lateral resolution,and type of the faults associated with the observed reservoir distribution.The results showed that the anomalously chaotic characteristics of the reflection energy of the strike-slip faults,highlighted on the seismic profiles,is actually the comprehensive effect of the fault widths and fragmentation degrees.On the other hand,the transverse resolution of the faults is not related to the characteristics of the overlying strata,while it is mainly affected by wavelet characteristics and other factors.If the absorption attenuation of the overlying strata is significant,the frequency band becomes narrower,the seismic wavelength longer,and the lateral resolution smaller.The fracture-dissolution reservoirs that formed in the fault zone do not show evident beading characteristics.In fact,large-scale karst caves,and caves developed at reflection interfaces,can indeed produce beads response,but it is still difficult to distinguish them from the chaotic reflection produced by the strike-slip faults.By comparing the model results with the actual seismic data,three typical fault modes were recognized in the Shunbei area:weak fault reflection,strong fault reflection,and chaotic fault flection associated with string beads.This classification can provide an effective reference for fault identification in this area,as well as a reference for the detection of strike-slip faults and the related karst fracture-cave reservoirs in similar areas.