Research On Seismic Sedimentology In The Chepaizi Uplift

Chepaizi uplift lies in the northwest of Junggar basin, which belongs to thesecondary tectonic unit of West Junggar upthrust, where is close to the Zhayermountain in the west and takes Hongche fault Belts as east boundary, while the southboundary is Sikeshu sag and Yilinheiergen mountain and with Kexia fault-foldingzone in the north. Chepaizi uplift is a single slope with southeast inclination, and hasgone through several subsidence repeatedly during Haixi periods with quite complextectonic development. There are lots of oil-gas reservoir in chepaizi area for thereason of special structures and sediments. The Cretaceous Formation is the targetformation in this research, which has erosion-unconformity contact with the upperShawan Formation of Neocene and overlap-uncomformity contact with underlieJurassic Formation.Based on the3D seismic data, well logging data and core data, taking the theoryof Seismic Sedimentary, Geophysics, Reservoir Sedimentary, Sequence Stratigraphyas the guide, and combined the results of predecessors, this paper focus on thetectonic, sequence stratigraphy, sedimentary facies study and carries out thecharacteristics of reservoir distribution of Chepaizi uplift. A set of well-seismicinterpretation method have been given. There are some results as below:(1) Based on the synthetic seismograms, using the vertical profiles, arbitrarylines, time-slicing technology and combining with well logging data, geological data,layer tracking have been done in3D space. By extracting the inclination cube,coherence cube, variance cube and ant cube, the fault displacement and the faultextension direction have been determined and the characteristics of the faultdistribution have been reflected. By combining drill data and seismic layers, spatialvariable velocity fields have been built to generate the tectonic map of Cretaceous Formation of Chepaizi uplift.(2) Based on the analysis of core data, logging data, seismic data, taking thetheory of Seismic Sequence Stratigraphy as the guide, combining the results ofpredecessors and considering the characteristics of the key layer, the CretaceousFormation has erosion-unconformity contact with the upper Shawan Formation ofNeocene and overlap-uncomformity contact with underlie Jurassic Formation. It iscomposed of one second-order sequence which can be further divided into4third-order sequence. They are Qingshuihe sequence, Hutubi sequence, Shengjinkousequence and Lianmuqin sequence, in decreasing age order. The CretaceousFormation also can be subdivided into three system tract: Lowstand SystemTract(LST), Trangressive System Tract(TST), and Highstand System Tract(HST). Thefirst flooding surface which is the mark of the LST is correspond to the top surface ofthe Qingshuihe sequence and the maximal flooding surface which is the mark of theHST is correspond to the top surface of the Shejinkou sequence.(3) Based on the logging data and seismic data, The Cretaceous Formationpalaeogeomorphology reconstruction of the Chepaizi uplift has been made. Theisochronous surface has been used to calculated the residual thickness. Back strippingtechnique is used in the recovery of the real thickness of the period of deposition.Acoustic time method and stratigraphic correlation method is used to restore the strataerosion thickness and the erosion part is decompacted in accordance with thecompacting factor. Finally, the ancient landform have been recovered by plus thecompaction correction thickness and erosion thickness. The result shows that theCretaceous Formation development in the slopes from west to east. In the northwestof the research area, the altitude is relatively high and the terrain is characterize ofundulating hills and valley. In the southwest of the research area, the altitude isrelatively low and the terrain is characterize of the combination of lower uplift and amidget mountain ridge, which form a narrow valley and a sag sedimentaryenvironment.(4) According to the different sedimentary system, particular seismic techniqueshave been employed to predict the different sedimentary system. The techniques of seismic facies analysis, attributes optimization and classification, geology carving in3D space have been used to analyze the fan delta system. The techniques of seismicforward modeling, attributes optimization and classification, frequency division,3Dvisualization have been applied to analyze the beach bar faices. Combing with thepaleogeomorphology analysis, the distribution of sedimentary system can be predictedaccurately.(5) A new method of acoustic curve reconstruction is proposed after an overallreview of existing research achievement. The multi-regression method and thediscrete wavelet transform have been combined to reconstruct the acoustic curve inorder to highlight the reservoir characteristic. Sparse Spike inversion has been used tocalculate the impedance, multi-attribute non-linear seismic inversion has beenemployed to improve the impedance inversion result and predict the distribution ofreservoir parameters. By combing the inversion results with logging interpretation andproduction data, the advantage area of oil exploration have been given in this article.