Studies Of Seismology On The Structure Characteristic And Advantaged Oil&Gas Accumulation In North Harbin Area Of Songliao Basin

The Songliao Basin, located in Northeast China (NE China), is a large scaleMesozoic-Cenozoic basin and the most important oil and gas concentrating region in China.The area of North Harbin located in Northern part of Songliao Basin between Harbin andNenjiang, and cover 6.4×104 km2, is important substitute of prospecting. The exploiting inthe area of Norward Harbin has been carried through for 40 years. Previously research wasonly localized in small scale and independence , and the degree of prospecting is lower.This paper synthetically analyzes wholly area of North Harbin about 40000 km2 and15 sections. Firstly with plate tectonics, studied the structural framework and tectonicevolution of fault depression in North Harbin area of Songliao Basin, by using four longseismic profiles and past geophysical and geological data. The main area of faultdepression of Songliao Basin lies in Xu Jiaweizi, He Yu-pao, Lin Dian, Gu Long and SanZhao area, whole present South is wide and deep, North is narrow and shallow. The faultdepression is divided into three tectonic units: Northwest uplift area, Southeast faultdepression area and central fault depression area according to some conditions such as: thedistributing under T4 layer (T4-T5), the undulation of basement, the basement and deeprift. Lindian fault depression in the central rift is the sedimentation central of North Harbinarea, which its beds develop full and mainly are sedimentary rock with a little volcanicrock, thereinto especially argillaceous rock is growth which is primary hydrocarbon sourcerock of North Harbin area.There are decades of basement rifts in North Harbin area, which are important on theframework structure of top layer and Oil & Gas concentrating. Most faults are in NNEand NE direction, including two suits inversion fault zone (every zone can be divided intotwo sub-zones, approximately be NE direction), and the layers change great. This indicatethat North Harbin area has been experienced extrusion action (even press) since lateCretaceous. Because there is few inversion fault in the basin of South Harbin and there area few suits small angle faults on sediment, we can draw a conclusion that there is a greatspace difference of the extrusion stress field encountered by whole upper crust betweenSouth area and North area of Songliao basin. Inversion fault belts can form local anticlinetectonic, which is avail Oil & Gas concentrating tectonic.Early and middle Jurassic basin which distribute in EW and NEE direction inNortheast area of China are related to northward dive, extend and extrusion inversion ofMongolia – Okhotsk ocean. Late Jurassic, the Songliao basin present late Jurassic layer isnot conformity with early Cretaceous layer due to the inversion close of Okhotsk ocean.Late Jurassic and early Cretaceous is the period that ancient Asia ocean tectonic area andWestern Pacific tectonic affect together. The tectonic movement of Mongolia – Okhotskocean tectonic belt determine the tectonic evolution of Songliao basin before Pacific platedive westwardly in Cretaceous. Because the study area was affected by Mongolia –Okhotsk ocean tectonic zone in rift period and affected by Pacific plate which divewestwardly in depression period, the tectonic of Songliao basin must be occur directioninversion, then form the control basin fault in direction NNE and NE.Synthesize the region tectonic in Northeast area affected by Mongolia – Okhotskocean, the basin evolution of North Harbin area can be divided into five parts: 1. Basementstick phase ( Trias ago)-ancient Asia ocean tectonic zone, including South branch close andstick and North branch-Okhotsk ocean began close. 2. Uplift phase (Trias-Early Jurassic)-plate stick and reciprocity. 3. Volcano-rift phase (Middle Jurassic-Early Cretaceous)-theeffect and control brought by the closing of Okhotsk ocean . 4. Region heat scratch-depression basin (Early Cretaceous-Late Cretaceous) -controlled by encircle Pacifictectonic zone, including rift transform to depression and depression period. 5. The transferand shrink of basin-controlled by circle Pacific tectonic zone .Although the development of North Harbin area experience rift, rift-depressiontransform, depression and shrink period too, it has distinct characteristic.1. The distributionof Denglouku Formation is local in rift-depression transform period.2. Yaojia Formationand its upper layer suffer great scale denudation in depression period, especially in East. 3.Although QingShankou Formation distribute all of the study region, its depth is shallow.4.The basin develop in a great in rift period, and there is deep depression .All thesecharacteristics show that the analysis of Oil & Gas concentrating belt should takeemphases on deep layer of rift and rift-depression transform period. According to the studyof tectonic in North Harbin, LinDian depression fault, MeiLisi depression fault, LanXidepression fault and BeiAn depression fault are favorable Oil&Gas concentrating belt.In search of big scale volcano Oil & Gas reservoir is the key of deep prospecting. Ithas important significance of identifying the tectonic enclose and analyzing the type andthe cause. Carrying through lithology forecast of basement in late Paleozoic and studyingthe formation evolution of basin is important too.On all accounts, there is enormous potentiality in North Harbin area of Songliao basin.From resource forecast result, the prospect future is good this area, but be affected bycomplex deposit environment and tectonic movement , the tectonic style is complex andreservoir is bad in this region, so the scale of Oil & Gas reservoir is small. Next step iscarrying through particular sequence stratigraphy study in selected region, and decideobscure enclose, then dispose explore well. In addition the cause mechanism research alsois a great value breakthrough of studying Songliao basin. On account of locating on theunite part of Eurasia plate, as well as be affected by Mongolia – Okhotsk ocean tectonicbelt associate with West Pacific tectonic zone, the mechanism of Songliao basin is verycomplex. No other than knowing and right realizing the tectonic cause and power resourcemechanism of Songliao basin, we can draw right conclusion on the local tectonic evolutionand favorable Oil & Gas concentrating belt.