| The research of paleodrainage system is of great significance for the exploration and development of carbonate
karst reservoirs. Based on restoration of paleogeomorphology, this paper utilizes the trend surface method, seismic
frequency division coherence attribute analysis, fine coherence attribute analysis of superimposed seismic profiles, and
RGB frequency division color mixing extracted along the weathered crust layer to delicately characterize the
paleodrainage system of Majiagou Formation on the top of Middle Ordovician in the Fuxian area. The results show that:
(1) The research area is located in the early Hercynian karstification zone, with a overall characterisic of being high in the
southwest and low in the north and east, and the paleogeomorphology can be divided into four third-class units: residual
hill, platform, terrace and trench. (2) Two types of palaeodrainage systems, surface and subsurface, are developed in the
study area. The surface palaeodrainage system is developed in the southwest high part (southwest region), which is nearly
symmetrical dendritic and dominated by deep-cut meandering currents. And the subsurface palaeodrainage system is
developed in the northeast structurally low part (northeast region), which is dominated by dark rivers and subterranean
flows, with stronger karstification and more collapses, and sinkholes. The surface and subsurface jointly constitute a deep-
cut meander-subterranean flow development model. (3) Karst remnant mounds and platforms are favorable areas for the
development of high-quality reservoirs. In this study, a variety of methods are used to describe the paleodrainage system,
overcoming the limitations of single technology. The combination of multiple morphological features enhances the
reliability of identifying surface and subsurface palaeodrainage systems, determines the development locations of
dominant reservoirs, and provides important reference significance for the exploration and development of the Lower
Palaeozoic in the study area. |
