A turbidite fan in the Eocene upper Wenchang Formation in the Enping Sag, Pearl River Mouth Basin （PRMB） has been studied using seismic, logging and borehole data. The fan is characterized by parallel progradation o...A turbidite fan in the Eocene upper Wenchang Formation in the Enping Sag, Pearl River Mouth Basin （PRMB） has been studied using seismic, logging and borehole data. The fan is characterized by parallel progradation on the dip seismic profile and is mound-shaped or lenticular-shaped on the strike seismic profile. The study of the core and logging data from well EP17-3-1, which is located in the front side of the turbidite fan, shows that this fan is a set of normal grading sand beds, interbedded within thick dark grey mudstones of semi-deep to deep lake deposits in the Wenchang Formation. The fan is interpreted as a sand/mud-rich turbidite fan that has an area of over 140 km2 and a maximum thickness of over 340 m. Combined with a study of the regional geological background and previous provenance analysis of the Eocene Wenchang Formation, the main potential provenances for the turbidite fan are considered to be the Panyu low-uplift and northern fault terrace zone. The Enping Sag is considered to be a half graben-like basin whose north side is faulted and whose south side is overlapped. Basement subsidence in the Eocene was mainly controlled by boundary faults which dip relatively steeply on the north side, causing the subsidence center of the Enping Sag in this stage to be close to the north boundary faults. Sustained faults developed in the Enping Sag during the Eocene caused an increase of the relative height difference between the north and the south uplift zone in the Enping Sag. Affected by the second episode of the Zhuqiong movement （39-36 Ma） in late Eocene, sediments which had accumulated on the Panyu low-uplift zone were triggered and moved toward the subsidence center of the Enping Sag and formed the turbidite fan. The second episode of the Zhuqiong movement is the most important triggering factor for the formation of the turbidite fan in the Wenchang Formation. Seismic attribute characterization shows that the low frequency energy is enhanced and high frequency energy is weakened when seismic waves propagate through the oil-bearing zone in this fan. Amplitude versus offset （AVO） anomalies are observed in the seismic data and abnormally high pressure is encountered. The turbidite fan in the Wenchang Formation has provided important information for sedimentary evolution in deep layers of the Enping Sag and pointed to a new direction for the hydrocarbon exploration in the study area.展开更多
Submarine or sub-lacustrine lobe deposits are important reservoirs,but the fan fringe deposits form heterogeneities within deep water fan deposits.Fan fringe facies records the complex sediment gravity flow types.By u...Submarine or sub-lacustrine lobe deposits are important reservoirs,but the fan fringe deposits form heterogeneities within deep water fan deposits.Fan fringe facies records the complex sediment gravity flow types.By understanding of the bed types and flow mechanisms,we can identify the fan fringe deposit,which aids in the reconstruction of deep water fan and reservoir evaluations.The Jiucaiyuanzi and Dalongkou sections in the West Bogda Mountains preserve well-exposed 536-m and 171-m thick successions,respectively,of a deep water lacustrine depositional system from the Middle Permian Lucaogou Formation.Bed types of the Lucaogou Formation include high-density turbidite,low-density turbidite,incomplete Bouma-type turbidite,hybrid event beds,and slump deposits.The Lucaogou Formation is interpreted here as a fan fringe facies due to the thin bed thickness that characterize turbidites and hybrid event beds,as well as the predominance of the isolated sheet architecture.Previous studies suggest that these deposits were considered as deposited in a deep water setting due to the absence of wave-related structures.The presence of abundant mud clasts in massive medium-coarse grained sandstone beds reflects the significant erosional capability and interactions between high-density turbidity currents and lake floor.The fan fringe facies here contains amalgamated and thick-bedded homolithic facies(~30%)and thin-bedded heterolithic facies(~70%).The examination of the bed type is of wider significance for facies prediction and reservoir heterogeneity in the sub-lacustrine fan fringe facies.展开更多
In the past 30 years, people have been paying attention to the relation between the deltas located on the slope of a basin border and the turbidite fans located in deep marine plain or deep lake plain, and have found ...In the past 30 years, people have been paying attention to the relation between the deltas located on the slope of a basin border and the turbidite fans located in deep marine plain or deep lake plain, and have found that the turbidites related to the deltas develop in lacustrine basins better than in marine basins. And, it is difficult to use the standard sub-展开更多
基金supported by the China National Science and Technology Project (2011ZX05025-006)
文摘A turbidite fan in the Eocene upper Wenchang Formation in the Enping Sag, Pearl River Mouth Basin （PRMB） has been studied using seismic, logging and borehole data. The fan is characterized by parallel progradation on the dip seismic profile and is mound-shaped or lenticular-shaped on the strike seismic profile. The study of the core and logging data from well EP17-3-1, which is located in the front side of the turbidite fan, shows that this fan is a set of normal grading sand beds, interbedded within thick dark grey mudstones of semi-deep to deep lake deposits in the Wenchang Formation. The fan is interpreted as a sand/mud-rich turbidite fan that has an area of over 140 km2 and a maximum thickness of over 340 m. Combined with a study of the regional geological background and previous provenance analysis of the Eocene Wenchang Formation, the main potential provenances for the turbidite fan are considered to be the Panyu low-uplift and northern fault terrace zone. The Enping Sag is considered to be a half graben-like basin whose north side is faulted and whose south side is overlapped. Basement subsidence in the Eocene was mainly controlled by boundary faults which dip relatively steeply on the north side, causing the subsidence center of the Enping Sag in this stage to be close to the north boundary faults. Sustained faults developed in the Enping Sag during the Eocene caused an increase of the relative height difference between the north and the south uplift zone in the Enping Sag. Affected by the second episode of the Zhuqiong movement （39-36 Ma） in late Eocene, sediments which had accumulated on the Panyu low-uplift zone were triggered and moved toward the subsidence center of the Enping Sag and formed the turbidite fan. The second episode of the Zhuqiong movement is the most important triggering factor for the formation of the turbidite fan in the Wenchang Formation. Seismic attribute characterization shows that the low frequency energy is enhanced and high frequency energy is weakened when seismic waves propagate through the oil-bearing zone in this fan. Amplitude versus offset （AVO） anomalies are observed in the seismic data and abnormally high pressure is encountered. The turbidite fan in the Wenchang Formation has provided important information for sedimentary evolution in deep layers of the Enping Sag and pointed to a new direction for the hydrocarbon exploration in the study area.
基金The study was funded by National Science and Technology Major Project(Grant No.2017ZX05001-002)National Natural Science Foundation of China(Grant No.41802129)。
文摘Submarine or sub-lacustrine lobe deposits are important reservoirs,but the fan fringe deposits form heterogeneities within deep water fan deposits.Fan fringe facies records the complex sediment gravity flow types.By understanding of the bed types and flow mechanisms,we can identify the fan fringe deposit,which aids in the reconstruction of deep water fan and reservoir evaluations.The Jiucaiyuanzi and Dalongkou sections in the West Bogda Mountains preserve well-exposed 536-m and 171-m thick successions,respectively,of a deep water lacustrine depositional system from the Middle Permian Lucaogou Formation.Bed types of the Lucaogou Formation include high-density turbidite,low-density turbidite,incomplete Bouma-type turbidite,hybrid event beds,and slump deposits.The Lucaogou Formation is interpreted here as a fan fringe facies due to the thin bed thickness that characterize turbidites and hybrid event beds,as well as the predominance of the isolated sheet architecture.Previous studies suggest that these deposits were considered as deposited in a deep water setting due to the absence of wave-related structures.The presence of abundant mud clasts in massive medium-coarse grained sandstone beds reflects the significant erosional capability and interactions between high-density turbidity currents and lake floor.The fan fringe facies here contains amalgamated and thick-bedded homolithic facies(~30%)and thin-bedded heterolithic facies(~70%).The examination of the bed type is of wider significance for facies prediction and reservoir heterogeneity in the sub-lacustrine fan fringe facies.
文摘In the past 30 years, people have been paying attention to the relation between the deltas located on the slope of a basin border and the turbidite fans located in deep marine plain or deep lake plain, and have found that the turbidites related to the deltas develop in lacustrine basins better than in marine basins. And, it is difficult to use the standard sub-
