Depositional Environment Assessment of the Middle Miocene Sedimentary Rocks in Thien Ung - Mang Cau Structure, Block 04 - 3, Nam Con Son Basin

Abstract

Sediment depositional environments are one of the important scientific bases in evaluation the reservoir potential of sedimentary rocks. This article focuses on studying this issue for Middle Miocene sediments, Thien Ung - Mang Cau structure, Block 04 - 3, Nam Con Son basin. The article has integrated the methods of well log interpretation, thin section analysis and seismic attribute analysis, combined with the results of paleontological analysis of VPI - Labs to identify depositional environments of Middle Miocene sediments in the case study area. The results of interpreting well log data show that the Middle Miocene sediments were deposited in the following environments: shallow marine, shoreline, mouth bars, delta front, prodelta and lower deltaic plain. These findings are also consistent with the results of petrographic and paleontological analysis. The results of petrographic analysis show that in the study area, there are 2 main groups of sedimentary rocks, which are clastic and carbonate rocks. In the thin sections, the following components were detected: glauconite clay is characterized of marine environment, carbonate fission and siderite ore which are characteristic of deltaic environments. While paleontological samples detected organic materials, such as algae, bitumen; and fossils such as Foraminifera, Da Gai and Oc Gai - typical for shallow marine environments. The results of the seismic attribute analysis for the Middle Miocene carbonate sediments of the structure have clarified that the carbonate is concentrated in the central and eastern uplift area. This distribution tends to fewer in the west. This finding is consistent when the authors compared to well correlation in the area (wells: C - 1X, C - 2X, C - 3X and C - 4X) and also logically with the sedimentary principles.