鄂尔多斯盆地寒武纪构造演化及油气地质意义OA

Successive breakthroughs in natural gas exploration in the Cambrian carbonate rocks of the Ordos Basin demonstrate the promising exploration prospects.Due to limited exploration degree,however,the tectonic evolutionary characteristics are less investigated,which restricts the understanding of deep oil and gas exploration.Based on field outcrops,drilling cores and seismic data,this paper systematically studies the seismic profile,fracture and tectonic evolutionary characteristics and their controls on gas accumulation in the Ordos Basin from the perspective of quantitative tectonic evolution,and then elaborates on the petroleum geological significance.The following results are obtained.First,during the Early Cambrian,under the influence of regional extensional tectonic settings and basement fault reactivation,the Fuping-Luochuan deep-water bay developed along the southern margin of the Ordos Basin,and the Yinchuan-Tongxin bay formed along the western margin,while the remaining areas exhibited the Ordos paleo-landmass characteristics.Second,during the Middle Cambrian,the Ordos paleo-landmass disintegrated into the Yimeng paleo-landmass,the Wushenqi paleo-uplift,the Qingyang paleo-uplift and the Lyuliang low-uplift,while the Shenmu East intra-platform depression developed in the northeastern part of the basin.Third,during the Late Cambrian,the Yimeng paleo-landmass,and the Wushenqi and Qingyang paleo-uplifts structurally merged to form a north-south-trending Central paleo-uplift,and the Lyuliang low-uplift disappeared.Fourth,during the Cambrian period,the Ordos Basin experienced two significant tectonic transformations,i.e.,the rift subsidence phase during the pre-Cambrian to Early Cambrian,and the compressional deformation phase during the Late Cambrian to the Late Ordovician.The deep-water bay along the southern margin of the basin and the Shenmu East intra-platform depression in the northeast jointly controlled the spatial distribution of Cambrian source rocks.The persistently developed paleo-uplifts within the basin have consistently served as favorable migration targets for hydrocarbons.Fifth,the regional unconformity surfaces formed at the base and top of the Cambrian strata during the Jixian Movement and Huaiyuan Movement,together with normal faults developed during the Cambrian period,collectively constitute a rapid migration pathway for hydrocarbon migration and accumulation.In conclusion,the tectonic evolution of marginal extension and late compression in the Ordos Basin during the Cambrian period controlled the distribution of source rocks,transport systems and paleo-uplifts,providing an important theoretical basis for natural gas exploration in this region.