The Study On Sequence,Sedimentary System And Reservoir Characteristics Of Eocene In Southwest Of Chaluhe Fault Depression,Yitong Basin

Based on the basic theories of Sedimentology and high resolution Sequence Stratigraphy,and by using core information,well logging,seism and analytical laboratory data,the author identifies in all levels of sub-base level cycles and analyzes deposition kinetics in this thesis.In response to short sedimentary source and multi-source of the faulted basin in the study area,a set of methods establishing continental rift basin Isochronous stratigraphic framework were explored.Yitong Basin Chaluhe Faulted Eocene was divided into 7 long-term base-level cycles,19 medium-term base-level cycles and the appropriate level of Isochronous stratigraphic framework is established,by which,a solid basis of stratigraphy is layed for the later sources analysis,depositional systems analysis and hydrocarbon enrichment patterns analysis.Under the control of the stratigraphic framework established,related to the stratigraphic architecture,sedimentary characteristics and seismic reflection parameters and the seismic reflection characteristics through well seismic analysis,geological significance is clarified by using well curve calibration to standardize the reflector shape.Layer-by-channel analysis of the fan body boundaries and type on seismic profiles is carried out and the source plane distribution map is completed then.Well line is to be calibrated in parallel and vertical provenance while taking advantage of the well point data of sand calibration,lithology planar distribution calibration and calibration of heavy minerals.At last source direction and range of distribution in 7 long-term base level cycle sequences is determined.The main source of rift comes from the northwestern margin and the southeastern margin is also determined,a small part of which is from the rise plate in No.2 fault.In addition,main source on Five Star tectonic belt in the rise plate in No.2 fault beyond the study area comes from the northwestern margin and the southeastern margin of Luxiang rift is revealed initially.Through analysis the characteristic of seismic section,it is mainly argued in this thesis is that that there are 5 kinds of sequence structure patterns in Chaluhe faulted depression under the control of basin margin fault and No.2 fault:?single fault steep sequence structure pattern,mainly distributing around the northwestern margin of Chaluhe,No.2 fault and Liangjia structural zone;?duplex fault sequence structure pattern,which is the feature of the plane section that crosscut Chaluhe fault depression.This pattern can be broadly divided into two:one is that there is no overlap and intersection of two fracture-controlled vertical sequence,the other is that the vertical overlay and intersection exists under the situation of more abundant source supply;?single fault flexure sequence structure pattern,this pattern develops around Wanchang area and No.2 fault,but it is special around No.2 fault because of the stress in the late North East;?fault ramp bottleneck sequence structure pattern,this pattern develops around Wanchang area due to local uplift causing thickness of the central of formation near the fracture thinner;?multistage fault sequence structure pattern,which develops around Wanchang area,this pattern is easy to form slump fan deposits and leads to thickening the three faults downthrown strata.Different patterns of the sequence structure control the distribution of sedimentary sources and sedimentary bodies,and affect their internal sedimentary characteristics,while hydrocarbon accumulation feature of different sequence patterns is diverse.On the basis of regional tectonics,sedimentary background knowledge,cores,logs,earthquake as a bridge,marks of various sedimentary facies are analyzed.Delta,nearshore subaqueous fan,slump fan,shoreface lake,deep lakes and semi-deep lake deposition are in the majority in Chaluhe fault depression,it is argued that in addition to being controlled by structural style and paleotopography of the sequence,specific facies types are tied into the relative height of water surface and both sides of the mountain and the terrain steep or slow mountains above the water surface while depositing.Nearshore subaqueous fan or slump fan is easy to form when it is steep,the fan delta is easier to form when it is moderate,slump fan in the study area is mainly due to gravity,tectonic movement,flow,caused shore subaqueous fan or fan delta the previously deposited and not consolidation slumping to the lake center formation,often corresponding to the distorted,messy seismic reflection characteristics.The fan body in Chaluhe fault depression is controlled by the basin margin faults and tectonic framework.,basically was the South East-North West trending,the fan bodies in southeastern margin of the terrain moderate extends farther,the fan body in the northwest edge of the steep terrain extends closer.But when the source supply of the Northwest edge is full,the onlap will be formed in the southeastern margin,and the material source at the same point is overlapping in the vertical.The thesis also studies and describes reservoir characteristics in detail.It argues that Chaluhe nearshore subaqueous fan is the most beneficial reservoir,the second is the top of neritic subsea apron and the middle of the slump fan,and the property of the rest facies is poor.The main reservoir types of the study area are lithology-fault reservoir,lithology-structure reservoir,basin margin fault,No.2 fault and precipitation facie are the main factors controlling hydrocarbon accumulation.The great development of the mud moundis is an important feature of Chaluhe fault depression,mud mound in the area is of great significance on the aggregation of oil and gas.The mud mound in mushroom shape not only blocks the oil and gas,prevents effusion,in E2s and E2sh,except oil' s vertical migration along faults and reservoir internal lateral migration,mud mound but also can be used as hydrocarbon source rocks directly supply the high-quality reservoir and in which it contacts with.Under the guidance of the above results,the beneficial areas in Chaluhe fault depression are predicted in this thesis.