Identification and Distribution of Jurassic Paleo-Reservoirs in the Central Junggar Basin, NW China

Abstract

Hydrocarbon generation and the expulsion of source rocks, tectonic evolution history, reservoir-seal assemblages, hydrocarbon accumulation stages and the distribution pattern of Jurassic reservoirs are discussed in this study. The Jurassic reservoirs were formed in the Early Cretaceous at the earliest. However, most of them were destroyed owing to the Himalayan tectonic movement which created formations tilted to the south in the Paleogene. Distribution pattern of paleo-reservoirs was critical for petroleum exploration and development in the Central Junggar Basin. In the Early Cretaceous, the paleo-structure of the Jurassic Sangonghe Formation was re-established. As a result, three paleo-uplifts (Muosuowan, Lunan and Luliang) were developed during this period, which had favorable reservoir forming conditions and controlled hydrocarbon distribution. Grains with oil inclusions (GOI) method were also used to study the distribution of Jurassic paleo-reservoirs. In some Jurassic layers, the GOI index was greater than 5% while these layers were identified as non-oil layers according to the logging and testing results. Thus, these layers may be a paleo-oil-reservoirs and were structurally destroyed during the Late Palaeogene. According to the comprehensive study of reservoir forming elements as well as GOI data, Jurassic paleo-reservoirs were mainly distributed in the Mosuowan, Lunan, and Luliang paleo-uplifts in the Central Junggar Basin.