Study On Tectonic Feature Of Delingha Depression In East Qaidam

Base on the full analysis to the existing data and current research efforts, this paper determined the distribution range of Carboniferous in Delingha Depression by field investigation combined with seisimic data, gravitational data, magnetic data and electrical prospecting data. In order to line with international stratigraphic divide practice, the transgressive surface after the regression event between Devonian and Carboniferous was taken as boundary of Devonian and Carboniferous. Carboniferous of Delingha Depression was divided into Lower Carboniferous and Upper Carboniferous two parts by using dichotomy. Former Middle Carboniferous Kluke formation was incorporated with Zhabusagaxiu Formation of Upper Carboniferous to form the new Upper Carboniferous. But the Amnik formation was classified into Devonian. Take the transgressive surface of Chuanshangou formation bottom as the basal surface of Carboniferous.Because there is little exploration well get to Carboniferous in Delingha Depression, this paper studied the fault feature and tectonic development feature of research region according to the seismic data combined with the gravitational, magnetic and electrical prospecting data. The tectonic framework of Delingha Depression is sag alternate with swell. Most of Carboniferous structure shows basement-involved unitized deformation controlled by later intense tectonic movement. According to analysis to section modality, horizontal distribution and deformational mechanism, Delingha Depression has 3 main tectonic styles and 12 basic styles. On this basis, Delingha Depression was divided into Delingha Sag, Olongbluk Swell, Aibei Sag and Amnik Swell four structural units.On the base of multidisciplinary analysis on Carboniferous lithofacies paleographic of Delingha Depression, this paper also studied its petroleum geological characteristics. Delingha sag has thick sedimentary rock, and with lower metamorphic rank. The contents of organic carbon is between 0.31and1.47%, and get to the standard of mediocre and good. Thick reef reservoir of Carboniferous with wide range was good reservoir. Piedmont tectonic belt of Olongbluk Mountain is near to Delingha Depression, and with intense tectonic deformation. It located in the saddle, are the most favorable oil accumulation structural belt. So it is most favorable place for prospecting.