The Analysis Of The Poolforming Features In The Upper Triassic Xujiahe Formation Of Western Sichuan Foreland Basin

The exploration potential of the upper Triassic Xujiahe Formation in the western Sichuan Foreland Basin is great.By means of the technologies of Basin Modeling, Petroleum System, and correlation among Chinese and foreign basins, and integrated analysis of the features of evolution of the basin, tectonic transformation, sidmentology, hydrology, and the anatomising of typical gas pools, The paper focused on the poolforming features of the basin, probed into the characteristics of enrichment, distribution and poolforming of oil and gas, and forecasted the favorable areas or belts of exploration. At the same time, attained following fruits:1. The tectonic analysis indicated that the distortion of the foreland basin was mainly attributed to the movements of Longmen Mountains, the structural features, forming periods, and transformation fashions are different between the northern and southern segments. And in the middle segment, landscape orientation faults exist.2. The paper put forward the particular mode of Sequence Stratigraphy in the foreland basin, which includes Lacustrine Margin Alluvial Systems Tract(AST), Lacustrine Expanding Systems Tract(LTST),and Lacustrine Highstand Systems Tract (LHST). The upper Triassic can be divided into three marine and one nonmarine sequences.3. By the integrating analysis of static and dynamic factors and distributions of oil and gas, combined with the researches on the source rocks and their geochemical features, basin modeling, and chemic and dynamic features of underground water, the paper brought forward clearly that there are three petroleum systems in the upper Triassic, which are T3x1- T3x2(!), T3x3~ T3x4(!), and T3x5~ J(!). The distributing and promising prospects are different among them.4. The series of J~K, T3x2 and T3x4 belong to independent water bearing systems. By studying, the paper brought forward the concept of Dynamic Geochemical Belts, and indicated that the high pressure gas bearing structures distributed in the areas of hydraulic pressure forming belts, the gas fields, such as Zhongba, Pingluoba, Hexingchang and Bajiaochang, distributed mainly in the discharge and stabilization belts, Guankou-Pingluoba and Daxing nose are the most promising prospects, and Laoguanmiao-Jiulongshan, Xiaoquan-Fenggu and Wenjiang-Shifang are the favorite ones.5. The distributions of source rocks, reserviors and faults/fissures, and conservation are the critical factors in poolforming and enrichment of gas in the foreland basin.6. The thrust belts of Longmen Mountains are potential prospects in the basin with the concentrated structural traps, strucrural-fissuring traps, and faults connecting between the shallow and middle formations.7. The deep depression of the foreland basin, where reserviors and source rocks interfingered together, is promising areas for the exploration of Deep Basin Gas and stratigraphic traps. Especially in the territories of Dayi-Mianzhu, Santai-Zitong-Yilong.8. The stable Foreland Slope and Forebulge are promising areas of structure-stratigraphy and upper pinchout traps.