Characteristics and evolution of the source-to-sink system of the Paleogene Wenchang Formation in Baiyun Sag，Pearl River Mouth Basin

The Pearl River Mouth Basin（PRMB）is a typical marginal sea basin to the east of the South China Sea. The Paleogene strata of the Baiyun Sag，a deep and large sag with well-developed Mesozoic-to-Cenozoic strata in the Zhu 域Depression of the PRMB，are the major targets for recent hydrocarbon exploration in the deep-water area. The Wenchang Formation is the hydrocarbon source rock sequence verified in exploration in the Baiyun Sag，and the provenances around the sag are also favorable for reservoir development. The quantitative characterization of the source-to-sink system，and the analysis of its characteristics and evolution of the formation provide a basis for predicting the distribution of the main hydrocarbon source rocks and large-scale sand bodies in the Baiyun Sag. A combination of zircon dating and heavy mineral analysis serves to determine the provenance system and its evolution. The types and distribution of transport channels are characterized by PSDM seismic data and palaeo-geomorphology. The characteristics of sedimentary system and sedimentary facies are depicted by well-tied seismic interpretation，while the source-channel-sink system is quantitatively coupled with the calculation results of palaeo-geomorphic relief，denudation thickness and sedimentary accumulation. The research results show that during the deposition of the Paleogene Wenchang Formation，there are four proximal provenance systems developed，that is，the Panyu low uplift，Yunli low uplift，Yundong low salient and Yunkai low salient，resulting in four complete suites ofsource-channel-sinksystems with fault-related ditches and ravines as channels. The source-to-sink system tends to undergo significant changes in different sedimentary periods. Under the effect of differential provenances in different periods，near-provenance braided river delta and fan delta deposits of small-scale lacustrine facies are developed in the Wenchang Formation of the Baiyun Sag as controlled by paleo-grooves and large-scale tectonic transition zones. The deposits of shore-shallow lake facies are widely developed in the 5th，4th and 3rd members of the Wenchang Formation under the control of the source-to-sink system of the Baiyun Sag. While the occurrence of semi-deep to deep lake facies is sparsely seen in the 5th member of the Wenchang Formation，and seen in the central of the 4th，3rd，and 2nd members，which provide a basis for predicting the distribution of the main hydrocarbon source rocks. Under the control of wide and gentle rift structure and large provenances，the braided river delta of sand-rich sedimentary system is developed on the north slope of Baiyun Sag that controls the planar distribution of large-scale sand bodies；the braided river deltas and fan deltas in the east of the Baiyun Sag are small in scale with sand bodies of favorable facies widely seen. © 2023 Editorial Department of Oil and Gas Geology. All rights reserved.