Sedimentary Sequence Of The Neogene And Controlling Factors In The Shelf Break Zone Of The Southeast Panyu Natural Gas Area

The southeast Panyu natural gas area is a long time in different tectonic settings of the shelf break zone,and it has an important role in restricting the development of sequence structure and the system tract.The shelf break zone and the lowstand syetem controlled by the shelf break are the most favorable condition for the formation of non-structural reservoirs.It is important significant for development and exploration of oilfield to study the sedimentary sequence of the Neogene and its controlling factors in the shelf break zone of the southeast Panyu natural gas area.On a basis of previous studies of the sepuence stratigraphic framework of zhujiang-hanjiang formation in the shelf break zone in southeast Panyu natural gas area,Pearl River Mouth basin,and comprehensively using well drilling,logging and seismic data and sequence stratigraphic principles,the characteristics of sedimentary sequence system tract and its controlling factors in the study area were studied.The main results and achievement are as follows:（1）According to the analysis of the feature of unconformity surface,the third-order sequence stratigraphic framework was established.zhujiang-hanjiang formation in this area is divided into seven third-order sequences,and each third-order sequence was subdivided into three to five forth-order sequences or systems tracts.On a basis of 3D seismic reflection datas and well loggings,the lowstand system tract of SQhj2 and SQzj2 can be recognized as two stages,and the late highstand system tract of SQhj1 developed the falling stage system tract.（2）Based on the comprehensive study of well loggings and cores,seismic facies and seismic sedimentology,the temporal and spatial evolution of the sedimentary facies is revealed.The sedimentary environments of zhujiang-hanjiang formtation in this area evolved from the littoral-braided river delta system,shallow-marine shelf-continental shelf slope to deep-water slope sedimentary system..The lowstand system tract of SQhj2 and SQzj2 are mainly of the deep dissected valley（incised channel）filling-type deposits,the shelf-margin delta（lowsand wedges）deposits,and the lowstand fan deposits.（3）Through the study of the basin paleogeomorphology,combined with the time isopach of system tract,sedimentary system feature and incised channel,the seismic reflection character of truncation/onlap,the horizontal distribution of the shelf break zone of the Neogene sequence in this area is identified.The shelf break zones of SQzj2～SQhj3 are steadily distributed in the north slope of Baiyun depression with a long term.The analysis shows that the structural evolution,paleogeomorphology,sedimentary source recharge and relative sea level change are the four factors which are very important to control the formation evolution of the shelf break zone in the study area.（4）On the basis of the sequence structure and depositional system tract were demonstrated,sedimentary sequence model of SQhj2 and SQzj2 were established.To carry out the study of the basin paleogeomorphology,synsedimentary fault and fracture slope break zone,tectonic subsidence,sediment supply and sea-level change controlling on depositional sequence evolution,reveals the main controlling factors of the depositional sequence formation of the Neogene in this area.（5）The favorable reservoir sand bodies and the distribution of lithologic and stratigraphic traps are predicted to provide reference for the petroleum exploration.