Youqi dizhi yu caishoulu (Nov 2023)
Classification of turbidite fans of Meishan Formation in Qiongdongnan Basin and their exploration significance
Abstract
The turbidite fans of Miocene Meishan Formation in Qiongdongnan Basin are important targets for natural gas exploration in the northern South China Sea， and the types of turbidite fan is closely related to reservoir development. The turbidite fans of Meishan Formation in Qiongdongnan Basin can be divided into shelf fans， slope fans， and basin floor fans according to the factors of sea level change， submarine topography， and syndepositional faults. The shelf fans at the shelf or shelf edge and the slope fans at the slope zone are mainly deposited in the highstand system and the late lowstand system respectively. The basin floor fans deposited in the early lowstand system can be further divided into six types： fault-terrace basin floor fan， final-terrace basin floor fan of fault-controlled gentle slopes， basin floor fan of fault-controlled steep slope roots， lobate basin floor fan， basin floor fan cut by canyons， and confined basin floor fan. The turbidite fan type and provenance system are important controlling factors affecting reservoirs’ physical properties. The reservoirs of fault-terrace basin floor fans， basin floor fans cut by canyon， and lobate basin floor fans are developed and are important exploration targets. Due to poor sedimentary differentiation and high mud content， the exploration risks are relatively large in the basin floor fans of fault-controlled steep slope roots， shelf fans， and slope fans. Final-terrace basin floor fans of fault-controlled gentle slopes and confined basin floor fans have fine grain and high mud content， which should be avoided in exploration. The various fan reservoirs are developed due to the sufficient provenance supply of Ledong-Lingshui area in the western part of Qiongdongnan Basin； however the excellent and high-quality reservoirs are underdeveloped due to the fine detrital particles and high mud content， and the lack provenance supply of Baodao area and Changchang area in the middle part of Qiongdongnan Basin， which are far away from the provenance area.
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