Pore structure is the key to understanding the shale gas accumulation mechanism. The effects of organic matter and maturity on pore size distribution and gas storage capacity in high-mature to post-mature shales are analyzed using gas adsorption (CO2, N2, and CH4), mercury intrusion porosimetry (MIP), and helium ion microscopy (HIM) for the Silurian Longmaxi and Cambrian Niutitang marine shales in southern China. The results show that the pores of high-mature Longmaxi shales with 2.32–2.42% Ro (vitrinite reflectance equivalent) are primarily composed of mesopores and macropores, whereas the pores of post-mature Niutitang shales with 3.49–3.66% Ro are primarily composed of mesopores and micropores. Organic matter clearly has a positive contribution to the micropore and mesopore development. In addition, increasing maturity appears to lower total porosity for post-mature shales, which has a lower total pore volume than that of high-mature shales. The free gas storage capacity of high-mature shales is controlled by the mesopores and macropores, whereas the free gas storage capacity of post-mature shales is controlled by the mesopores and micropores. The adsorbed gas storage capacity for both high-mature and post-mature shales is primarily controlled by the micropores.

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The process and mechanisms of secondary hydrocarbon migration in the Tazhong uplift, Tarim Basin, were investigated based on the analysis of the regional structure and by integrating geologic, hydrodynamic, and geochemical parameters. Parameters successfully analyzed included the fluid potential, fluid properties, production outputs, and diamantane index. The results indicated that hydrocarbons migrated into the Tazhong uplift from the northern part of the Manjiaer depression through a series of injection points (IPs) during four orogenies, that is, the early Caledonian (510 Ma), the late Caledonian (439 Ma), the late Hercynian-Indosinian (290 Ma), and the Yanshanian-Himalayan (208 Ma). A total of six IPs were identified at the intersections of the northeast-trending faults and the northwest-trending flower strike faults. The hydrocarbons migrated from the IPs into traps along regional trends from northwest to southeast and from northeast to southwest. The hydrocarbon migration process and patterns determined the distribution of hydrocarbon properties and production rates in the Tazhong uplift. With increasing distance from the IPs, daily hydrocarbon production decreases, and the hydrocarbons become progressively heavier and display lower gas:oil ratios.

Apatite Fission Track (AFT) data from the Songliao Basin indicates that the late stage tectonic movements in the Songliao Basin have zoning in space and episodes in time.The late stage tectonic movements started from the east part of the basin and migrated westward. AFT ages in the east part of the basin are older than those in the west part of the basin, suggesting that the uplift occurred earlier in the east than in the west. The denudation thickness in the east part of the basin is significantly greater than that in the centre and west. The thermal history evolved two episodes of rapid cooling and subsequent slow cooling processes. Age-depth relationship derived from the AFT data indicates a four-episode denudation history. Further Monte Carlo random simulation of the AFT data reveals the four changing points of the thermal evolution at 65 Ma, 43.5 Ma, 28 Ma and 15 Ma, respectively. The uplifting and denudation rates from different episodes of evolution are proportional to the plate convergence rate. Based on the above analyses and the regional geologic background, it is concluded that the late stage thermal events in the Songliao Basin are the far field response to the subduction of the Pacific Plate under the Eurasian Plate. The first episode of the rapid cooling probably started at the end of the Nenjiang Formation, climaxed at the end of the Cretaceous and ceased at the Late Eocene. The subsequent slow cooling lasts another 15 Ma. The first episode of the evolution is the far field response to the major episode of the Yanshan Movement and subsequent series of the tectonic reorganization, especially the directional change of the Pacific Movement and also the subduction of the Indian Plate underneath the Eurasian Plate. While the second episode of the evolution is the far field response to the extension and closure of the Sea of Japan. Extension led to the migration and converging of the mantle heat flow to the Sea of Japan and resulted in the rapid cooling of the Songliao Basin.apatite fission track, late stage tectonic movement, episodic movement, plate tectonics, Songliao BasinThe thermal history of the sedimentary basins is a reflection of the tectonic evolution process, which controls the hydrocarbon evolution, migration and accumulation and the reservoir quality [1] . Zircon and Apatite Fission Track analysis is the most common method to obtain the geochronology information contained in the sediments, to trace the sediment provenance, and to quantitatively calculate the denudation history of the mountains [2][3][4] .With the improvement of the technique, multiparameters were used to study complicated uplifting and denudation history [5,6] , for example the AFT ages, the confined mean track length and the track length distributions. Former researchers have routinely analyzed the thermal history of the Songliao Basin, especially the

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