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The Upper Triassic tight sand oil in the Ordos Basin has gradually become a focus of research; however, compared to the centre of the basin, studies on the margin have been relatively weak. In this study, an integrated approach involving oil–source correlation, charge history, and pressure evolution is used to investigate the migration characteristics of each stage and to establish a migration and accumulation process model of the tight sand oil in the Yanchang Formation of Honghe Oilfield in combination with reservoir densification process. The results show that, based on the fluid inclusion analysis and authigenic illite K–Ar dating technique in combination with burial and thermal modellings, the accumulation periods were 145–130, 120–90, and 90–80 Ma, which corresponds to the Cretaceous. According to the relative content of C30‐diahopane and drimane series compounds, the crude oil from Chang 8(T3ch8) and Chang 9(T3ch9) both originated from the oil shale of Chang 7(T3ch7) in the Upper Triassic Yanchang Formation. The migration characteristics and directions are comprehensively analyzed using the maturity parameters and key elements. In the early stage of the Early Cretaceous, with east‐dipping strata, crude oil migrated from northeast to southwest. During the late Early Cretaceous, the middle‐late Yanshanian movement promoted the development of strike‐slip faults and fractures, and the oil migrated vertically downwards along them. Tectonic inversion changed the strata dip direction to west‐dipping, and lateral migration was also changed to two directions of southwest and northeast. After the Late Cretaceous, the migration dynamics weakened due to strata uplift and cessation of hydrocarbon generation. Only slight adjustments to the crude oil occurred during the Himalayan movement; therefore, the current distribution pattern of the tight sand oil is still affected primarily by the stage of late Early Cretaceous. The migration and accumulation model of the Upper Triassic in the Honghe Oilfield, Ordos Basin, provides a theoretical basis for further exploration and is of general applicability to tight sand reservoirs in the margins of various basins. [ABSTRACT FROM AUTHOR]

Middle and lower Ordovician carbonate rock in the Tabei Uplift of the Tarim Basin forms important fractured reservoir beds. Core and log data indicate that tectonic fractures, as the main fractures in the Tabei Uplift, could be mainly classified into two types: oblique fractures and approximately vertical fractures. The fractures are mainly NNW-trending and NNE-trending, coincident with the large faults nearby. Fracture abundance was also controlled by lithology, and faults nearby played a significant role. Cores, thin sections and tests show that these carbonate rocks have as much as 2.5% fracture porosity and as much as 150 md fracture permeability. Based on the intersection of fractures in cores, together with fluid inclusion temperature data, and the timing of faulting from seismic profiles, tectonic fractures were considered to be mainly formed in three periods: the late Silurian when the first-stage oblique fractures were formed, the late Permian when approximately vertical fractures were formed, and the late Tertiary when the second-stage oblique fractures were formed. Lower Cambrian source rocks started to enter the stage of generous hydrocarbon generation and expulsion in the Silurian. Ordovician source rocks started to enter the stage of generous hydrocarbon generation and expulsion in the Permian and enter the over-mature stage in the late Tertiary when light oil was generated. Timing of tectonic fractures formation and burial history analysis suggest that fractures formation might coincide with oil accumulation when fractures provided the pathway and storage space for the low permeability and low porosity reservoir beds caused by previous compaction and cementation. Considering the presence of a large amount of fracture-developed dolomite in the deeper Ordovician Penglaiba Formation, the undrilled Penglaiba Formation should be paid more attention. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]