Abstract:

Carboniferous is another favourable hydrocarbon source rocks in the eastern section of North Qaidam, besides the Jurassic. There are some conflicts between the drilling data and the previous view that Carboniferous deposited in broad basin and the residue stratum distributed in some of the present sag. The author made full use of the achievement data such as field geological investigation, drilling, seismic, electrical, etc. By using the methods of the outcrops, drilling calibration, seismic facies and velocity spectrum recognition, we traced and interpreted the top and bottom interface of the Carboniferous. The distribution of Carboniferous residual stratum of the eastern section of North Qaidam has been redetermined. According to the balanced section, the characteristics of basin tectonic evolution were analyzed and its impact on the Carboniferous strata distribution were explored. The results show that there was a complete transgressive sedimentary cycle in Carboniferous of the eastern section of Qaidam. Residual stratum is mainly distributed in the western section of Gaqiu sag and eastern section of Ounan sag, Huobuxun sag and Delinha sag. There is almost no Carboniferous residual in the western section of GaxiYuqia sag，MahaiDahonggou salient, Dachaidan sag and HongshanXiaochaidan sag. The Carboniferous residual strata distribution is controlled by the tectonic movement in the later period of IndoChinese epoch. Affected by the YanshanianHimalayan tectonic movement, there were strong separation in the distribution of Carboniferous residual stratum.

Key words: controlling factors, tectonic evolution, residual stratum distribution, Carboniferous, eastern section of north Qaidam