Comparative Study On Soft Sediment Deformation From Xihu Sag In East China Sea Basin And Mahu Sag In Junggar Basin

Xihusag is located in the northeast East China Sea shelf basin,adjacent to the Diaoyu islandsfold zone,and it is fault basin that is eastern fault and west overlap,the Paleogene Pinghu formation and Huagang formation is development in the overall regression background.Mahu sag is located in the northwestern margin of Junggar basin,Northwest China were relying on Wuxia fault zone and Baike fault zone,it's a secondary tectonic unit in the central sag,and the Triassic Baikouquan formation is a set of fan delta deposits.Through the observation of nearly 1000 meters of cores in Xihu sag,and nearly 2000 meters of core in Mahu sag,author found that the main goal horizons of the two research areas have developed a large number of soft sediment deformation.It mainly developed deformation structure including: brecciated structure,intrusion structure,water escape structure,fold deformation structure,ball and pillow structure and the load structure etc.Based on previous research results and ideas,according to the objective care data and subjective though,explaining thesoft sedimentdeformation in the two different research area from aspect of deformation structure lithology,development scale,morphological characteristics,and the formation mechanism etc.According to the sedimentary environment and tectonic background from two research areas,combined with the distribution of sediment deformation structure analysis showed:(1)Most of the wells withsoft sediment deformation structure in Xihu sag of is mainly distributed in the fracture around,and contrasted the different well-connecting lineswiththe deformation characteristics,author found its features and distribution have regularly changes in accordance with the causal mechanism elements for the tectonic movement,so it is indicated that the causal mechanism is the tectonic movement.A few other wells,in Pinghu formation,have some soft sediment deformation structureaccompanied with the tidal bedding,anddo not have the causal mechanism elements for the tectonic movement,sothe trigger mechanism of the deformation structuresmost probably are the tidal movement;(2)Most of soft sediment deformation in Mahu sag developed in the delta front subfacies,and the mainly SSD structures are intrusive structures,load structures and ball-pillow structures.sothe causal of soft sediment deformation in the research area is likely the overpressure induced by tectonic movement and unbalanced pressure.Due to the difference of sedimentary environment and tectonic background of the distrinct research area,resulted soft deformation structures in two research areas are different from many aspects:growing type,lithology,scale and formation mechanism etc.(1)Soft sediment deformation structure in Pinghu formation and Huagang formation of Xihu sag are mainly developed in the sand-mud fine sediments,and soft sediment deformation structure in Baikouquan formation of Mahu sagare mainly developed in gravel coarse sediments;(2)The all typical soft sediment deformation types have beendeveloped in two in the research area,but the forms of each type deformation has a little difference,mainly difference is the fine sediment deformation and coarse sediment deformation;(3)The sand-mud fine sedimentmore easily liquefied deformation,resulting the deformation structures in the Pinghu formation and Huagang formation of Xihu sag is more extensive and larger scale;(4)SSD Structures in the research areas are concentrated in the delta front subfacies.The sedimentary strata is the record carrier of ancient events,drawing support from sediment and structural knowledge,identifying and resolving the sediment deformation structures of the old strata can not only help the researchers speculateancient events information of the location,intensity and timeet al,it is also could provide strong evidence to resume the ancient sedimentary environment.Researching the soft sediment deformation is helpful to the exploration and development of oil and gas has important effect:(1)the sediment deformation could expanded the reservoir space,also could improved the permeability.According to the physical properties of the research area,the influence of different SSD structure in the reservoir are also different.Micro fractures,micro faults and intrusive structures can efficient improve the porosity and permeability of reservoirs;(2)The deformation structure could be a favorable lithologic stratigraphic trap;the great energy released by trigger event could improve the migration speed,(3)and some deformation structure could be used as a good migration channel;(4)it may lead hazards of rapid losingand streaming of oil-gas et al.