| Due to the lacking of systematic research on the tectonic-sedimentary response of Wenchang Formation
in northern Huizhou Sag, Pearl River Mouth Basin, the exploration process is seriously restricted. Based on the new
high-resolution 3D seismic data and new wells, the tectonic-sedimentary response and its control over high-quality
source rocks in northern Huizhou Sag are deeply analyzed through well-seismic joint interpretation. It is considered
that: (1) Mainly controlled by the spatio-temporal evolution of the sag-controlling faults and the tectonic response of the
Huizhou movement, the tectonic and sedimentary characteristics of each sub-sag in Huibei area are significantly different
in Wenchang period. Huizhou-08 and Huizhou-14 sub-sags are characterized by graben with weak tectonic activity in
Wenchang period, and braided river deltas and shallow lacustrine facies are developed under the influence of the
provenance of Huizhou-08 transition zone outside the basin. Huizhou-10 sub-sag is a half graben with the strongest
tectonic activity in Wenchang period, and semi deep-deep lacustrine and braided river delta are developed under the
influence of the provenance of the Huilu Low Uplift. (2) The differential coupling of tectonic evolution and sedimentary
characteristics leads to the "east-west zoning" of sources rocks of Wenchang Formation. Source rocks of shallow
lacustrine-swamp facies are mainly developed in Huizhou-08 and Huizhou-14 sub-sags, and the high-quality source
rocks of semi deep-deep lacustrine facies are mainly distributed in Huizhou-10 sub-sag. (3) The development models of
source rocks of Huizhou-10 sub-sag in different period are different. During the strong rift period, Huizhou-10 sub-sag
was connected with the adjacent sub-sag, and most of the provenance in the gentle slope zone was under water, which
resulting in a large accommodation space and little sediment source input, consequently the semi deep-deep lacustrine
facies are developed extensively throughout the sub-sag. About 43 Ma, the magma intrusion induced by the Huizhou
movement caused a high-angle rotation of the gentle slope zone of Huizhou-10 sub-sag, and the current dustpan-shaped
half-graben formed, which greatly reduced the scope of the lake during the atrophic rift period, and the semi deep-deep
lacustrine deposits only develop near the controlling faults. This study has great significance to the next exploration in this
area. At the same time, it gives a unique case of tectonic-sedimentary evolution of half graben. |
