2026/08/01 by Pu Wei, Lei Fu, Zhengbing Yang +6
paper · doi:10.17491/jgsi.2026.174449
crossref created 2026/07/14 · crossref issued 2026/08/01 · crossref published 2026/08/01 · crossref published-online 2026/08/01 · crossref published-print 2026/08/01 · crossref deposited 2026/08/02 · crossref indexed 2026/08/02
ABSTRACT Recent drilling in the Sangonghe Formation (J1s2) of the Shixi Uplift, Junggar Basin, has revealed significant tight oil potential; however, a systematic understanding of the factors controlling reservoir quality remains limited. This study aims to comprehensively characterise these tight sandstone reservoirs and identify the primary geological controls on “sweet spot” development. Using an integrated approach combining core analysis, thin-section petrography, Scanning Electron Microscopy (SEM), and high-pressure Mercury Injection Capillary Pressure (MICP) tests on samples from 18 wells, we established a quantitative hierarchical control model. Results indicate that the J1s2 reservoirs are dominated by lithic sandstones deposited in braided river delta front environments. Sedimentary facies exert the primary control (Tier 1) on reservoir quality; underwater distributary channels (porosity >12%, permeability >4.2×10−3 μm2) exhibit superior properties due to low muddy matrix content (<8%) and coarse grain size. Diagenesis acts as a secondary modulator (Tier 2); quantitative porosity reconstruction shows that mechanical compaction is the dominant destructive factor (accounting for 55–80% of porosity loss), while carbonate cementation causes localised occlusion (15–30%). Crucially, MICP analysis reveals a distinct vertical heterogeneity: the lower sand-group (J1s22) possesses average pore-throat radii (0.64–10.24 μm) significantly larger than the upper sand-group (0.32–2.46 μm), explaining its threefold higher permeability. The novelty of this study lies in the quantitative differentiation of vertically stacked sand-groups, linking micro-scale pore structure to macro-scale facies architecture. We identified five favourable exploration zones covering ~145 km2, with estimated resources of 25–60 million tonnes. These findings demonstrate that facies-controlled initial porosity sets the reservoir potential, while the intensity of Eodiagenesis and early Mesodiagenesis modifies the final quality, providing a replicable workflow for predicting “sweet spots” in analogous tight sandstone basins globally.