Study On The Sedimentary Characteristics Of The Sanjianfang Formation In The Eastern Taipei Sag,Tuha Basin

Turpan-Hami Basin is a petroliferous basin with a certain amount of oil and gas resources discovered in the 1990s in China.It is known for its pioneering discovery of large-and medium-sized coal-to-oil and gas fields in the Jurassic.The structural position of the Hongtai gas field is located in the Hongtai structural belt of the Xiaocaohu depression in the eastern part of the Taibei depression of the Turpan-Hami basin,and is currently in an integrated rolling development stage of exploration and development.Starting with the establishment of the stratigraphic framework,this paper uses various basic data,such as 3D seismic data,logging data,and core data,to analyze the sandbody distribution and sedimentary microfacies of the Sanjianfang Formation in the Hongtai area of the eastern part of the Taibei sag.The law of plane and section spread was studied in detail.In this study,a relatively stable shale layer was used as a marker layer.The Sanjianfang Formation was divided into five gas group groups:S₁,S₂,S₃,S₄,and S₅.The structural characteristics of the study area were studied accordingly.The study suggests that the study area has a good inheritance and similarity from the bottom up structure,and a southwest tilting nose structure is developed in the central part of the study area,with the western part of the area being steep and the southeast part steep.According to various sedimentary facies marks,the sedimentary facies types of the Sanjianfang Formation in Taipei depression were identified and divided.According to the study,the Hongtai area is mainly composed of two sub-facies of the braided river delta plain and its front edge.The braided river delta plain develops dif-ferent channel and inter-flow bay microfacies;the braided river delta front mainly develops underwater distributary channels and Diversion bay microfacies.The study area mainly receives source sediments in both the South East and the North West,and the South East source mainly.Affected by provenance,sediments in the S₄ gas layer group mainly come from the braided river delta plains in the southeast and northwest directions;sediments in the S₃ gas layer group mainly come from the braided river delta plains in the southeast and northwest directions.And the deposition of the two subphases of the front edge;the NW-trending channel of the S2 gas layer group disappeared,and the distribution range of the composite river channel in the southeast expanded;at the same time,the braided river delta plain and its front edge were deposited in the southeast direction;S₁ gas The stratum group is the largest gas stratum group in the Sanjiangfang Formation of the Middle Jurassic,and the deposition of the braided river delta front is more developed.