A micrograph dataset of buried hills and overlying glutenite in Bozhong Sag, Bohai Bay Basin

Bohai Bay basin is adjacent to Jiaoliao uplift area in the East, Taihang mountain uplift area in the west, and restricted by Luxi uplift area and Yanshan fold belt in the north and south respectively. It is an irregular rhombic basin with an area of about 20 × 104 km2. It is a large superimposed (or residual) basin superimposed on the pre Cenozoic craton basin. A large number of buried hills are developed in the pre Cenozoic basement. In 2017, the bz19-6 buried hill in the Southwest Ring of Bozhong achieved a major exploration breakthrough, and large-scale massive structure condensate gas reservoir was found in the Archean buried hill and its overlying conglomerates of Kongdian formation. This paper reports 201 pieces of metamorphic granite in Archean buried hill of Bozhong sag of Bohai Bay Basin and its overlying glutenite thin sections of Kongdian formation of Paleogene. It is revealed that the deep buried hill reservoir in bz19-6 structural belt is a pan buried hill reservoir system composed of Archean buried hill metamorphic granite and overlying Paleogene Kongdian Formation glutenite, forming glutenite pore zone and dissolution fracture of weathering crust of buried hill The multi-level reservoir structure of belt + inner fracture zone + tight belt has complex genesis and various types. The part of metamorphic granite in the atlas shows that the mineral composition of buried hill is composed of dark minerals such as quartz, feldspar and a small amount of biotite. Vertically, the reservoir can be divided into weathering crust, internal fracture zone and tight zone, with the dual characteristics of fracture type as the main type and pore type as the auxiliary. The weathering crust of buried hill is affected by strong dissolution leaching and superimposed fracture, forming fracture pore reservoir space. The reservoir space of the inner fracture zone is dominated by felsic brittle mineral structural fractures and fracture dissolution expansion. The atlas shows that Kongdian of Paleogene is mainly composed of clastic rocks, with high terrigenous clastic content, a small amount of Mesozoic volcanic rocks and low content of heterobase. It is a clean "rich sand and poor mud" near source sedimentary body, which is a typical "sieve deposition", and its main controlling factor is late dissolution. Through the systematic study of microscopic thin sections of rocks, the differential development of fractures caused by lithologic changes in bz19-6 pan buried hill reservoir system is clarified, and the effect of reservoir dissolution and transformation by lithology and fluid is identified, which lays a petrological foundation for the further exploration of oil and gas in the Bohai buried hill, and provides valuable petrological materials for the in-depth study of the destruction of the North China Craton.