«Proceedings of Gubkin University»

Postsedimentary transformations of sandstones from the lower eocene basal sedimmentary sandstones in the southeastern part of the Jiyang depression (the Bohaiwan, China)

UDC: 552.14
DOI: 10.33285/2073-9028-2022-4(309)-5-16

Authors:

¹ Lomonosov Moscow State University, Moscow, Russian Federation)

Keywords: sandstones, post-sedimentary processes, compaction, mineral formation, mineral dissolution, metasomatism, transformation model

Annotation:

This paper mainly analyzes the post-sedimentary secondary transformations of the Lower Eocene basal sandstones in the southeastern part of Jiyang depression. The Jiyang depression is located in the southeastern part of the Bohai Bay Basin in China, where a set of clastic rocks mainly composed of red, reddish-brown, gray and variegated sediments are deposited in the Lower Eocene. Based on the study of a large amount of core data, this paper analyzes the transformation of the internal structure of sandy reservoirs during the process of compaction, the formation of new minerals, erosion and dissolution of minerals. On this basis, the diagenetic transformation model of the sand body in the study area is established. It was found that for active secondary transformation of sand bodies in post-sedimentary processes, the following two conditions must be met: 1) a relatively large thickness of the sand body; 2) the presence of large faults connecting sand bodies and oil and gas source rocks. The fan delta front sandbodies distributed in the gentle slope zone preserve a large number of primary pores and form a large number of secondary pores during the post-sedimentary process, which can be used as good hydrocarbon storage space. The gentle slope zone can be used as a key area for further exploration in the Jiyang Depression.

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