Source-to-sink Systems Analysis Of The Paleogene Enping Formation, Baiyun Sag, Pearl River Mouth Basin

Source-to-sink systems analysis sprung up in study of sedimentation of continental margin and began one of the worldwide hotspots. It is known as the basis of semi-quantitative research of depositional system and reflects the importance of the earth’s surface dynamics process revealing the earth’s overall dynamic process. According to the research of provenance, channel and depositional system spatial and temporal distribution of the Paleogene Enping Formation, Baiyun Sag, the difference of source-to-sink systems in different period was researched and four different source-to-sink systems coupled models were established, which has an important reference on prediction of reservoir and prospect of lithologic traps of the Paleogene Enping Formation, Baiyun Sag.Based on seismic data and comprehensive research of detrital zircon U-Pb dating of source tracing, recognize of provenance channel, seismic facies-attribute analysis and sand body boundaries track, provenance and sedimentary filling in different period of Enping Formation were cleared. Referencing outcrop data of typical fan delta, braided delta and channel, source-to-sink systems coupled models in different period of Enping Formation were built.The main results obtained in the papers as followings:1) Build a sequence framework of Enping Formation, Baiyun Sag.Seismic stratigraphic unites and characters were recognized according to terminal manners of seismic reflection and the differences of interior seismic facies. The sequence recognition of upper Enping Formation was synthetically used single well, paleontological and seismic data. Enping Formation was divided into three three-order sequence, SQ72, SQ71 and SQ70. Two second-order sequence boundaries, T80 and T70, and two third-order sequence boundaries, T71 and T72, were recognized. T80, which was a truncation unconformity, was the boundary of Wenchang Formation and Enping Formation. The reflection ending of T72 was mainly downlap. T71 was a sedimentary transfer boundary of Enping Formation. T70 was a Fault depression conversion surface of Baiyun Sag and mainly low-angle truncation. From sequence SQ72 to sequence SQ70, the structure activity of Baiyun Sag was weakened. The area of every sequence gradually expanded. This offered a clear sequence framework for study of source-to-sink system of Enping Formation, Baiyun Sag.2) Ascertain provenance way and scale in different sedimentary period of Enping Formation, Baiyun Sag. (Source)During deposition of mid-lower Enping Formation, the provenance was short and dispersed offered by Mesozoic igneous basement rock. The provenance supply of south steep slope belt was relatively small, which was from Yunkai uplift and South swell. The provenance supply of the both sides of north gentle slope belt was relatively large, which was from Panyu uplift. During deposition of upper Enping Formation, the provenance was mainly from Precambrian-Paleozoic metamorphic rocks of south China fold belt. The structure activity of south steep slope belt was weakened. Yunkai uplift began to accept deposition. And the provenance from south swell was weakened. The provenance of north gentle slope belt was from both south China fold belt and Panyu uplift and developed large scale NW-SE braided delta from slope to center.3) Ascertain channel pattern of Enping Formaiton, Baiyun Sag. (Channel)According to recognize of Negative landscape units, three types of channels, ancient valley surrounding uplift, trench in north gentle slope belt and south structural transfer zone, were ascertained and main source feeding direction of different sedimentary period of Enping Formation was clear.4) Discuss spatial-temporal distribution of sedimentary system of Enping Formation, Baiyun Sag. (Sink)Based on single well facies, seismic facies and attribution analysis, the pattern and spatial-temoral distribution of sedimentary system in three-order sequence were determined, and the response characteristics of sedimentary filling in different tectonic settings and different source supply were specific. During deposition of mid-lower Enping Formation, south steep slope belt mainly developed fan delta. Both sides of north gentle slope belt developed braided delta and beach bar reformed by waves and shore current. During deposition of upper Enping Formation, north gentle slope belt mainly developed three NW-SE braided delta with typical foreset reflection.5) Build source-to-sink systems coupled models in different period of Enping Formation.Based on characteristics of source-to-sink coupled models in different period of Enping Formation, four source-to-sink coupled models were built:south steep slope belt-structural transfer zone-fan delta, north slope belt-ancient trench-braided channel filling complex and north slope belt-wave reforming-beach bar in period of deposition mid- lower Enping, Formation and north uplift-ancient valley-braided delta in period of upper Enping, Formation deposition. Based on source-to-sink systems analysis, sequence stratigraphy, structural geography background, provenance channel and way, sedimentary system constituent feature and space distribution are merged, which increased reliability of reservoir prediction without wells or with few wells.