AUTHOR=Lu Hao , Cao Song , Dong Shaoqun , Lyu Wenya , Zeng Lianbo 

TITLE=Control of lamination on bedding-parallel fractures in tight sandstone reservoirs: the seventh member of the upper Triassic Yanchang Formation in the Ordos Basin, China

JOURNAL=Frontiers in Earth Science

VOLUME=Volume 12 - 2024

YEAR=2024

URL=https://www.frontiersin.org/journals/earth-science/articles/10.3389/feart.2024.1428316

DOI=10.3389/feart.2024.1428316

ISSN=2296-6463

ABSTRACT=The tight oil sandstone in the 7th member of the upper Triassic Yanchang Formation in the Ordos Basin, China, has low porosity and permeability. Bedding-parallel fractures play a crucial role in enhancing reservoir and flow capacity. Based on core and thin section data, most bedding-parallel fractures are unfilled, with apertures generally <40μm, mainly <10μm. Larger apertures correlate with smaller filling ratios. The distribution of BPFs is intricately governed by laminations' types, density, and thickness. (1) The degree of development of bedding-parallel fractures depends on the degree of difference in mechanical properties between adjacent laminations; (2) When the laminations density is within a range, as the laminations density increases, the bedding-parallel fractures also increase; When the density of the laminations continues to increase beyond this range, the degree of fracture of the bedding-parallel fractures decreases; (3) Bedding-parallel fractures in thick laminations mainly distribute along the edges, while in thin laminations, they mainly distribute in the middle. The change in the thickness of the laminations leads to a change in the development position of bedding-parallel fractures, indicating that the position of the plastic plane controls the development position of beddingparallel fractures; (4) When multiple laminations coexist, the type and thickness of the laminations jointly influence the development of bedding-parallel fractures. Plastic thin laminations are conducive to the development of bedding-parallel fractures, while brittle thick laminations are not conducive to the formation of bedding-parallel fractures. When the thickness of the plastic laminations is close to or less than that of the brittle laminations, the laminations type has a dominant influence on bedding-parallel fractures, conversely, the influence of laminations thickness on bedding-parallel fractures will be dominant.