Division of Glutenite Lithofacies Based on the Trielement of Gravel-Matrix-Fracture

In recent years, glutenite oil and gas reservoir exploration has continuously made major discoveries, making the conglomerate body a new field of oil and gas exploration. At present, the conglomerate body is focused on sedimentary response analysis, and its characteristics of lithofacies combination division and differences are relatively weak, and there is a lack of a unified division standard, especially in the Paleogene in the southern slope area of the Bonan low uplift in the Bohai Bay basin. There are multiple gravel components and composite diagenesis in the sandy conglomerate, which greatly restricts the distribution prediction and evaluation of high-quality sandy conglomerate reservoir. Due to the multiple sources of supply in the study area, the gravel composition, support type and matrix type are diverse. Based on the typical drilling core in the area, comprehensive observation under the microscope and scanning electron microscope analysis, it proposes the "three parent rocks of sedimentary rock, metamorphic rock and magmatic rock. The type is the first-level classification standard, and the support type and matrix type are the second-level classification standards." The sandstone and conglomerate lithofacies are divided into three major categories and seven subcategories, followed by (1) matrix support mainly based on volcanic matrix support-sand-level matrix-structural fracture-conglomerate facies, particle support-sand-level matrix-intra-gravel fracture-conglomerate facies, matrix support-mud-level matrix-conglomerate facies, (2) matrix support mainly composed of carbonate conglomerate-sand-level matrix-conglomerate facies (carbonate rock and gravel), matrix support-sand grade matrix-breccia facies, (3) cement support mainly composed of metamorphic rock and gravel-sand grade matrix-concrete sandstone facies, and particle support-sand grade matrix-gravel-edge fracture-concrete sandstone facies. In reservoirs of different gravel types, the matrix type and fracture development degree are obviously different. The reservoir with high mud content has poor permeability. The fracture development will improve the connectivity of its pores and induce the formation of intra-gravel dissolution and matrix dissolution to improve storage properties.