Dissolution characteristics and impact on properties of the He 8 Reservoirs in the Yanchuan Area

doi:10.3969/j.issn.1006-6535.2025.03.006

Abstract

Abstract: To address the unclear impact of dissolution on the properties of the He 8 Reservoir in the Yanchuan Area of the Ordos Basin, this study used mercury injection, porosity and permeability tests, core observation, thin-section identification, and scanning electron microscopy to analyze the development characteristics of He 8 sandstone reservoir dissolution and its impact on reservoir properties. The results show that the He 8 Member is a typical ultra-low-porosity, tight reservoir divided into three types: quartz sandstone, lithic quartz sandstone, and lithic sandstone. The reservoir has undergone intense diagenesis, with dissolution being the main factor for secondary pore formation and property enhancement. All three reservoir types experienced acidic dissolution during the late early diagenetic stage B to the middle diagenetic stage A. Quartz sandstone reservoirs, with low soluble components and weak dissolution, mainly have intergranular pores. Lithic quartz sandstone, strongly dissolved, forms high-quality reservoirs with abundant secondary pores. Lithic sandstone, subjected to strong compaction rock chip deformation resulting in densification of the sandstone, is a tight reservoir. A dissolution development model was established based on sandstone type. The study results offer a significant reference for "sweet spot" differentiation and favorable area prediction in the He 8 tight sandstone reservoir.

Key words: dissolution, development characteristics, reservoir properties, He 8 Member, Yanchuan Area, Ordos Basin

CLC Number:

TE122.2

HUANG Xingyu, DU Guichao, HE Yawen, GUO Ruiliang, ZHU Lin, JIA Wenhao, WANG Hao, WANG Fengqin. Dissolution characteristics and impact on properties of the He 8 Reservoirs in the Yanchuan Area[J]. Special Oil & Gas Reservoirs, 2025, 32(3): 47-56.

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