New understandings and exploration discovery of Paleogene reservoirs of Kunbei fault terrace belt, Qaidam Basin, NW China

Abstract

The sedimentary facies distribution, sedimentary reservoir characteristics and main control factors of Paleogene Lulehe Formation and Lower Xiaganchaigou Formation were examined by studying on the Paleogene reservoir properties of Kunbei fault terrace belt in western Qaidam Basin, combined with well logging and seismic data. Because of the source control by Kunlun Mountains, the Lower Xiaganchaigou Formation developed braided river delta−lake sedimentary systems, mainly braided river delta front sediments, and the sand bodies distribution is SW-NE; the Lower Lulehe Formation mainly developed braided river delta plain, and braided river delta front mainly developed in the Upper Lulehe Formation. The reservoir physical properties of the braided river delta front in Lower Xiaganchaigou Formation are better, with favorable conditions of high-quality reservoirs. Tight reservoirs in Lulehe Formation have sweet spots. The oil and gas distribution of Lulehe Formation in Kunbei fault terrace belt is controlled by the content of argillaceous matrix. The new understandings of sedimentary reservoirs in Kunbei fault terrace belt play an important guiding role in oil and gas exploration of the area. Oil and gas exploration in the Qie 6, Qie 12 and Qie 16 structures achieves success, with almost one hundred million tons of proven geological reserves. Key words: Qaidam Basin, Kunbei fault terrace belt, Paleogene, sedimentary facies, reservoir characteristics, new area exploration