Positive Inversion Tectonics Genetic Mechanism And Its Reservoir Forming Control In Rifting Basins

Positive inversion tectonics in rifting basins, means that tectonism occurred reverse change, from extension to contraction, it’s a kind of superimposed tectonic. In this paper, we typed the classification of inversion tectonics, made clear its genetic mechanism and kinematics model, summarized three quantitative methods and its forming control on reservoir. Then take Wuerxun-beier sag in Hailaer basin for example, to apply the results to them, finally get the region’s positive inversion tectonics genetic mechanism and its reservoir forming control.According to the standard of pre-structure’s geometric shape, positive inversion tectonics in rifting basins can be divided into two categories, the fault type and the fold type. The fault type can be divided into four subtypes, they are listric faults control, ramp-flat faults control, domino fault systems control and graben control. These kind of types are all develop in Hailaer basin, Wuerxun-beier sag, but their distribution are different.The positive inversion tectonics genetic mechanism mainly controled by fluid pressure, rock friction coefficient, pre-exist normal fault dip, and the obliquity between pre-exist normal fault strike and compression. In study area, faults dip are all≤60°, pre-exist normal fault strike are almost NE-trending, the compression stress are EW-trending, so the included angle is near 45°, these all meet the conditions of genetic mechanism, thus positive inversion tectonics widely distributed in study area.Use inversion ratio, fault throw profile with growth index, and isopach thinning ratio these three methods can accurately reflect rifting basins positive inversion tectonics’ inversion degree. The first two are using in the fault type inversion tectonic, the last one is using in the fold type inversion tectonic. Apply these methods to the study area, we can learn that the two sag’s inversion degree are ditterent, and different kind of inversion types, different pre-exist fault strike, may have different inversion degree.Combination the positive inversion tectonics types, genetic mechanism, quantitative methods, can obtain positive inversion tectonics forming control on reservoir. Considering from two aspects of plane and profile, at the study area, in the plane, the secondary hydrocarbon reservoir mainly develop on the listric faults control inversion structural zone, then the ramp-flat faults control inversion structural zone, the strike of pre-exist faults are general NEE-trending, at the middle of the fault section. In the profile, the secondary hydrocarbon reservoir accumulate as the umbrella type.