Study Of Tectonic Evolution And Rule Of Oil-gas Accumulation In He'an Area In The Dongpu Depression

He'an area , which lies in the middle of the Central Uplift of Dongpu Depression,is one of the most important petroleum exploration target areas in the south ofinclining and extinguishing edge of Wenliu tectonics. Problems like the complextectonics, low degree in tectonic studies, shallow knowledge of petroleum migrationand concentration as well as the poor cognition of rule and mode of pool formingrestrict the exploration process in this area. So it is of vital importance to reinforce theintegrated study in tectonic evolution and the concentration rule of petroleum in thisarea to help the oil and gas exploration.Starting with the basic petroleum and geological character and regarding thetectonic evolution, the sorts of oil and gas pool and the factors of controlling oil andgas concentration as the main study content, the paper set up a petroleumconcentration mode in fault-zone and found out the oil and gas concentration rule andpointed out the exploration direction in this area. Through integrated researches,active progress was made in conditions and rules in forming pools.He'an area has two different strata sequences. Controlled by faults, thesedimentary character in plane is that strata in the west are thicker than those in theeast, and thin in the high place and evidently thick in the saddle of the tectonics. Thechanges of tectonic layer from late Carboniferous to middle Tri controlled the tectonicevolution and oil and gas conentration in Paleogene in the northern Central Uplift ofDongpu Depression. The strike in this area has changed twice (from NNE to NE toNNE). In regard of tectonic evolution, under the outstretching background, there grewseveral series of opposite-strike faults in early time and those faults finally formed agraben. Later, complicated by the uplift of the middle, the tectonics formed twoinverted ridge zones in both east and west. The differences in stress field from Liuhaistructures to Langzhongji structures made the differences between the two tectonicareas in tectonic distribution, tectonic development as well as oil and gas migration.With more profound petroleum geology researches, it is deemed that this areahas two generative cycle and two main oil and gas migrating times and they are verymatchable in both space and time. Tectonic evolution and tectonic style control thedistribution of oil and gas concentration areas. Along the faults oil and gasconcentrated to the high place of fault-block and they exist in lower Es₂ strata and midEs₃ strata in longitudinal.There are 1.38×10⁸t resources not found in He'an area so far, which mainly existin Wenxi fault-belt and Huanghe fault-belt. According to the oil and gas concentrationcharacter, the first main target is lower Es₂ strata and the second main target is Es3strata.