Research On Polygonal Faults Genetic Mechanism And Controlling Petroleum Migration And Accumulation Of Putaohua Reservoirs In Sanzhao Depression

On the base-of the analysis of the faulting geometrical feature which developed on the top (T11 reflection) and bottom (T11 reflection) of Qingshankou formation in the Sanzhao depression of Songliao basin, we systematically interpret the kinematics feature and the genetic mechanism of faults, and find that the high density faults on the T2 reflecting stratum formed by tectonic mechanism.under the action of WE orientation extensive stress field, it is intensive fault zones affected by oblique rifting,differential extension function,basement faults and volcanic vent in the early Qingshankou formation.There are many differences on the development characteristics between the high density faults on the T11 reflecting stratum in the northern and southern of studied areas.The faults in the northern areas distributed in the form of concentration zones as well, preferential strike orientations are near SN, and it mainly formed by tectonic mechanism. Faults on the T11 reflecting layer have a good inherited relationship with T2. While faults in the southern areas have typical features of polygonal fault systerms, which displays multi-strike directions and intersected with each other in plan view to form cellular polygons, that can not be explained easily only by tectonic evolution history. Based on the comparison with the basins worldwide which develop the typical polygonal faults,we think they are the faults formed by non-tectonic mechanism because of the mudstone density inversion induced by tectonic movement.According to the analysis of faults genetic mechanisms, we studied the relationships of oil-water distribution and faults in Putaohua oil layer of Sanzhao depression, based on producing data of nearly 4000 wells, we can see that the faults with two different genetic mechanisms control different oil-water relationships in southern and northern areas respectively. In the northern areas of Sanzhao depression, intensive fault belts controlling the distribution of oil,oil wells often distribute near the intersection of two faults, and out of the fault belts,oil wells distribute near the intersection of two fault belts as well, so in a word, the essence of the intensive fault belts controlling the distribution of oil is that fault intersections control the distribution of petroleum,the distribution model is that low part is water and upper part is oil in longitudinal direction in Songfangtun oil field and Shengping oil field because of undersupplying oil source and fault multiphase activities.Polygonal faults distributed in the southern areas, and oil field connect widespread. Intersections are also the oil vertical migration predominant pathways,but along with the release of abnormal pressure, polygonal faults are active frequently and oil migration along them vertically,owing to the main mechanisms for increasing the hydrocarbon source rocks pressure is hydrocarbon generation,so polygonal faults have a strong power of petroleum migrating, oil source is sufficient,the oil frequently charged the Putaohua oil formation along intersection of faults,and all strata are oil-bearing,that is the main reasons which make the difference of oil-bearing strata and oil saturation between northern and southern part.Under the guide of mechanism that fault control the oil field, Hydrocarbon accumulation models which is controlled by polygonal faults is that oil migrated vertically along the intersection of faults,then migrated laterally in sandstone with short distance, accumulated by sealing faults and lithologic boundary barrier, the representative oil fields are Zhaozhou oil field.