New discoveries and exploration prospects of middle and Lower Jurassic lithologic reservoirs in depression area of Turpan-Hami Basin, China

Abstract

Recently found substantial discoveries in the Lower Jurassic Sangonghe Formation in Taibei Sag, Turpan-Hami Basin was made possible through exploration wells Qintan1 and Ji7H. The two wells represented a major breakthrough in lithologic oil and gas reservoir exploration in the depression area and offered promising results for the investigation of the “lower depression source” in the Turpan-Hami Basin. The two favorable conditions of lithologic reservoir formation in the sag area are systematically summarized based on the two wells, and specific suggestions for further exploration are specified. The results show that: (1)Three sets of source rocks, namely Badaowan Formation, Sangonghe Formation, and Xishanyao Formation, are developed in Shuixigou Group of Jurassic in Taipei Sag. The new drillings reveal that Sangonghe Formation serves as both a regional caprock and a high-quality source rock. According to the source rock re-evaluation, the Shuixigou Group in Taipei Sag has excellent hydrocarbon generation potential. (2)Sangonghe Formation of Lower Jurassic is the main target layer for exploration in the depression area. Braided river delta sediments are developed. Sandbodies are developed in the depression area. At a depth of more than 5000 m, effective reservoirs are still developed as a result of secondary dissolution and structural fractures. (3)There are five favorable zones of rock reservoirs in the Lower Jurassic of Taibei Sag, namely, Pudong, Hongbei, Lingbei, Qiudong, and Gebei. These zones have excellent exploration potential and represent an important direction for future exploration in the Turpan-Hami Basin.