限定性峡谷和非限定性峡谷沉积充填过程模拟——以琼东南盆地M区为例

Simulation of sedimentary filling process of confined and unconfined canyons:taking the Area M of Qiongdongnan Basin as an example

峡谷内砂泥比沉积充填速率的变化直接影响峡谷的地貌特征。以琼东南盆地M区中央峡谷为例,基于1000 km^(2)三维地震资料,研究了该区7个时期形成的峡谷类型并进行了划分。利用Fluent流体仿真软件模拟了在单物源和双物源条件下峡谷内不同砂泥比条件下充填过程的沉积特征。结果表明:早期(T50—T30)形成的峡谷为限定性峡谷,晚期(T29_1—T29)形成的峡谷为非限定性峡谷。限定性峡谷内发育的水道弯曲能力较强,多期水道叠置作用明显,多发育水道复合体;而非限定性峡谷内发育的水道多以横向迁移为主,水道在开阔地带则会缓慢扩散形成朵体复合体。通过峡谷充填过程的模拟和研究提高了峡谷内沉积单元识别的准确性,为提高勘探目标区域的优选效率提供了理论依据。

The changes in the sand-mud ratio and sediment-filling rate in underwater canyon directly affect the geomorphic characteristics of the canyon.Taking the Central Canyon in the Area M of the Qiongdongnan Basin as an example,based on 1000 km^(2)of three-dimensional seismic data,the canyon types formed in seven periods in the area were recognized and classified.Software Fluent was used to simulate the characteristics of the filling process under the conditions of different sand-mud ratios in single-and dual-sourced scenarios.Results show that the canyons that formed in the early stage(T50-T30)are confined canyons,and the those formed in the late stage(T29_1-T29)are unconfined canyons.The channels developed in the confined canyons have strong meandering ability,the superposition of multi-stage channels is obvious,and channel complexes are mostly developed;however,in the unconfined canyons,channels developed are mainly transversely migrated,and then slowly diffused into an open area and formed lobe complexes.The simulation and study of the canyon-filling processes increased the accuracy of identification of sedimentary units in the canyons,and provided a theoretical basis for the efficiency and the optimization of exploration target areas.