| Author's Name: ZHANG Ronghu1, JIN Wudi2, ZHI Fengqin1, ZENG Qinglu1, YU Chaofeng1,
WANG Bin3, WANG Ke1, LI Dong1, ZHOU Shijie1 |
| The tight gas resource potential of the Lower Jurassic Ahe Formation in Dibei area of the eastern Kuqa
Depression is enormous, making it a promising region for increasing oil and gas reserves and production. For a long time,
the coupling relationship between sweet spot model and oil and gas enrichment of tight sandstone reservoir in Ahe
Formation is unclear, which restricts the efficient exploration and development of tight oil and gas reservoirs.Based on
microscopic reservoir characterization, geological modeling, fault-fracture characterization and reservoir analysis, this
paper investigates the sweet spot characteristics and hydrocarbon enrichment patterns of tight sandstone reservoirs in the
Ahe Formation, and evaluates their resource potential. The study reveals that the Ahe Formation reservoirs exhibit an
alternating distribution of tight layers and low-porosity / high-permeability zones laterally. Reservoir properties are
significantly enhanced by fault-fracture modification, developing sweet spot areas at four hierarchical scales. The
fracture-pore systems controlled by class I-II faults extend east-west direction, characterized by large scale and favorable
porosity-permeability properties. The fracture-pore systems controlled by class Ⅲ-Ⅳ faults/ fractures are small in scale
and pinch out within tight sandstones. The first hydrocarbon charging event in the Ahe Formation reservoirs occurred
between 18 and 12 Ma, with porosity ranging from 15% to 18% during this phase. The primary charging fluid was crude
oil, which accumulated in structural highs to form conventional oil reservoirs. However, these reservoirs were
subsequently severely disrupted, leading to complete dissipation of the accumulated hydrocarbons. The second
hydrocarbon charging phase commenced since 5 Ma, during which the reservoir underwent rapid densification, with
porosity reduced to 6%-8%. Natural gas efficiently migrated along faults and fractures, accumulating preferentially within
sweet spot zones of the reservoir. Class Ⅲ and Ⅳ faults/fractures zones establish effective connectivity between sandstone
units within the Ahe Formation, forming optimal configurations with adjacent tight reservoirs and overlying mudstones.
These structural features constitute critical controls on both trap effectiveness and hydrocarbon accumulation. The
favorable area for oil and gas enrichment in tight sandstone of the Ahe Formation can reach 106 km2, mainly concentrated in
the central and southern platform areas of the Dibei Slope. The lithological trap resources of natural gas are 1 699 × 108 m3
and petroleum are 778 × 104 t |
