Actividad de fallas segmentadas como mecanismo impulsor de la migración lateral multifásica de deltas de abanico: Un estudio de caso en los estratos del Paleógeno del Bloque G, depresión Wenchang, Mar de China Meridional

Resumen

The fan delta in the steep slope zone of a rift lake basin is an important oil and gas reservoir unit. The development of vertical multi-stage fan deltas has certain inheritance and vertical non-overlapping characteristics. The driving mechanism of the overall lateral migration of such multi-stage fan deltas is currently not completely clear. Taking the fan delta in the Paleogene steep slope zone of Block G in the Wenchang Sag in the northern South China Sea as the research object, based on core, logging, drilling data and high-precision 3D seismic data, using seismic facies analysis and fault displacement-rate analysis techniques to analyze the driving effect of fault segmentation activities on the lateral migration of the fan delta. The results show that: (1) The vertical multi-stage fan deltas show inherited development characteristics, and the plane shows lateral migration characteristics, with a migration rate of 0.1-0.5 km/Ma; (2) The center position of the fan delta is highly correlated with the low-velocity zone of fault activity, and 80% of the research samples are distributed in the low-velocity zone of fault activity; (3) The migration of the fan delta shows a two-stage driving characteristic of "fault-dominated positioning - geomorphic dynamic regulation". In the early stage, the segmented activity of the fault controls the injection position of the detritus in the uplift area into the lake basin. After the detritus enters the lake, it locally transforms the accommodation space in the basin, dynamically adjusts the sedimentary geomorphology, and then reshapes the sedimentary path and drives the lateral migration of the fan body.