Through systematic organic geochemistry analysis, the main hydrocarbon source rocks of terrestrial formation in northeastern Sichuan are systematically evaluated, sources of oil are determined by carefully comparison of geochemical characteristics between source rocks and oil, and accumulation characteristics are identified. Analysis results indicate that terrestrial formations, such as Group Xujiahe, Ziliujing and Qianfoya, develop vast effective, even rich source rocks with high organic matter abundance, and the average TOC values of different districts and groups range from 0.41% to 2.99%. Type Ⅱ and type Ⅲ are widely distributed, and source rocks are high mature to over mature with Ro ranging from 1.3% to 2.0%. Generally, hydrocarbon source rock of terrestrial formation in northeastern Sichuan has high hydrocarbon generation potential, which could be favorable main source rocks of middle and lower Jurassic terrestrial unconventional oil and gas in research area. Comparison of geochemical characteristics between source rocks and oil and accumulation characteristics analysis demonstrate that middle and lower Jurassic terrestrial unconventi onal oil and gas are generated from terrestrial sources with few marine sources, which proves that oil and gas migration difficulty caused by the extremely tight terrestrial reservoirs leads to in-source or near-source accumulation. Oil and gas in group Qianfoya are from Ziliujing source rocks and that in group Ziliujing are from both Ziliujing and Xujiahe source rocks in Yuanba-langzhong. Oil and gas are all from Xujiahe source rocks in Xuanhan-daxian. Lower Jurassic shale can fill the requirements for shale gas, while middle and lower Jurassic tight sandstone can fill the requirements for tight sandstone oil.

Characteristic and origin of “spherical particle” are studied based on contrast analysis of petrography and carbon and oxygen isotope of “spherical particles” in basite drawn from well and typical amygdules in basalt sampled in the field. Results show that “spherical particles” and amygdules are significantly different in microscopic and carbon and oxygen isotopic characteristics although they are similar in macroscopic feature. “Spherical particles” are characterized by non-oscillatory zoning, obvious recrystallization in the rim, and different carbon and oxygen isotopic values in different “spherical particle” of the same sample. Amygdules are characterized by oscillatory zoning, big crystalline particle, and similar carbon and oxygen isotopic values in different amygdule of the same sample. It can be concluded that “spherical particle” stems from magma capturing pieces of sedimentary carbonate, rather than secondary minerals filling vent. As a result, the basite drilled from the Cambrian and Carboniferous strata is intrusive rock, and volcanism may not occur in related strata.

Petrology, mineralogy and geochemistry method such as thin section, cast thin section, scanning electron microscope observation, cathodoluminescence, energy spectrum and major element experiment were used to analyze the genesis of Permian volcanic reservoir in Yuenan Region, Tarim Basin. It is found that Permian volcanic reservoir, dominated by secondary pore space can be regarded as favorable reservoir because the porosity of the primary pore space can reach 14% and 13.1×10^?3 μm² respectively. Genesis of the secondary pore and cracks is the weathering, whose intensity increases with the depth decreasing. The porosity and the permeability is positively correlated to weathering. The thickness of weathering effect can reach at least 220 m. The weathering dissolution and leaching process take priority of weak plane, such as large number of primary pores, cooling contracted crack, cryptoexplosion fracture which generate in the cooling of volcanic and cleavage crack, twin stitch of primary mineral. Weathering sequence of feldspar phenocryst and matrix is found in rhyolite, weathering products are mainly illite, with small amounts of montmorillonite, and the entire sequence of clay minerals growth process is preserved. Weathering can modify substantially pore structure on the basis of primary porosity, and improve the porosity and permeability greatly, which is the main controlling factor of Permian volcanic reservoir of Yuenan Region, Tarim Basin.