The Characteristics Of Tight Oil Reservoir And Favorable Exploration Area Prediction Of Paleogene And Neogene In The Southwestern Area, Qaidam Basin

By means of sedimentary petrology, lithofacies paleogeography, petroleum geology, mineral petrology and organic geochemistry, sedimentary facies characteristics, characteristics of hydrocarbon source rock distribution and density of reservoir have been researched in the southwest of Qaidam Basin. Combining with the depositional environment of dense oil development, high-quality hydrocarbon source rocks distribution and density of reservoir development area, analysis the control factors of the dense oil, a favorable oil exploration region is further predicted.1. There are two kinds of sedimentary system of Paleogene and Neogene have developed in the southwestern, Qaidam Basin. The mainly developed fan depositional is delta–lacustrine system in the northeastern, the major depositional system is braided delta–lacustrine deposit in the southwestern.2. According to the reservoir characteristics, Two tight reservoir favorable zones are mainly distributed in southwestern Qaidam Basin:(1) The main reservoir type of the upper Xiaganchaigou Formation is carbonate in Qigequan–Shaxi–Gasi area, its lithology is primarily argillaceous limestone, the reservoir space mainly consists of intergranular pore;(2) The main reservoir type in the lower Xiaganchaigou Formation is clastic rock in Zhahaquan–Wunan area, the lithology is primarily feldspathic debris sandstone and rock fragment feldspathic sandstone, reservoir space development of primary pore, secondary pore, micropore and nanoscale hole, reservoir space also has better filtration capacity.3. Comprehensive analysis of the test results of Toc, Chloroform bitumen "A", Vitrinite reflectance(Ro), Kerogen types and Rock pyrolysis, the research area is divided into 3 high-quality hydrocarbon source rocks distribution zone:(1) Source rocks in Shangganchaigou Formation are mainly distributed in the Hongshi sag, Zhahaquan sag and Wunan slope in Southwestern Qaidam Basin;(2) Source rocks in the upper segment of XiaGanchaigou Formation are mainly distributed in the Qigequan–Hongliuquan slope, Hongshi sag, Shaxi–Gasi slope, Zhahaquan sag and Wunan slope in Southwestern Qaidam Basin;(3) Source rocks in the lower segment of Xiaganchaigou formation are mainly distributed in the Zhahaquan sag and Wunan slope in Southwestern Qaidam Basin.