Analysis of sedimentary mechanisms of the channel-fan system in the 2nd Member of the Huangliu Formation at the Yingqiong Junction, Yinggehai Basin

With the increasing degree of exploration in the mature areas such as the Dongfang District and Ledong District of the Yinggehai Basin, there is an urgent need to find new areas for reserve growth. The Yingqiong Junction in the Yinggehai Basin is characterized by low degree of exploration. The middle-deep Huangliu Formation in this area has favorable hydrocarbon source and migration conditions, and the axial channel-fan system is well-developed, making it an important practical area for increasing reserves and production. However, the low precision of sedimentary facies research and unclear dynamic sedimentary evolution mechanism in this area have seriously restricted the exploration progress. Based on the establishment of a sequence stratigraphic framework, we systematically investigated the sedimentary mechanisms of the axial channel-fan system in the second member of the Huangliu Formation at the Yingqiong Junction by fully utilizing core, 3D seismic and other data. Results show that in the early stage of the lowstand systems tract (LST) of the second member of the Huangliu Formation, the restricted axial channels were mainly developed in the study area; in the middle-late stage of the LST, axial channel-submarine fan deposits were widely developed; during the transgressive systems tract (TST) and highstand systems tract (HST), channel-submarine fan deposits developed hereditarily but in reduced scale and high argillaceous content. The "activation of underlying fault fracture zones and regional sea level fall" is the main controlling factor for the incision and formation of axial channels, and the "large-scale provenance sand supply - main channel convergence and transformation - branch channel sand transport - micro-paleotopography fan control" is the important mechanism for the development of large-scale fans outside the channels. During the middle-late stage of the LST of the second member of the Huangliu Formation, an axial channel-submarine fan lobe complex deposit developed that are mainly from Hainan Island and characterized by multi-branch channel convergence, which is the key target and important direction for the exploration of high-quality reservoirs in the middle-deep layers of the Yingqiong Junction.