Petroleum geological features and exploration prospect of Linhe Depression in Hetao Basin, China

Abstract

After over four decades of exploration, a major breakthrough has been made in the Hetao Basin recently, that is, commercial oil flow of 62.6 m3/d is tested from the Paleogene Linhe Formation in Well Song 5. A comprehensive study of petroleum geological features of the Linhe Depression reveals that the Langshan fault, Hangwu fault and Huanghe fault controlled the deposition and evolution of the depression and hydrocarbon generation center, and the basin experienced Early Cretaceous depression and Cenozoic faulting. There developed two sets of saline lake hydrocarbon source rocks, Cretaceous Guyang Formation and Paleogene Linhe Formation. The source rocks, dominantly type II1 and I, have high abundance of organic matter and large potential of hydrocarbon generation, and their maturity ranges from low mature to over mature owing to wide variation of burial depth. The Guyang Formation and Linhe Formation are the clastic reservoirs, which have good physical properties with burial depth less than 5 000 m. In the Jixi uplift, the weathering fractures in matrix also have storage capacity. Faulted block, faulted anticline and matrix fracture reservoirs are found through exploration. The low mature to mature oil, is generated from Guyang Formation and Linhe Formation. The study shows that the Linhe Depression has rich resources and huge exploration potential, where the main exploration targets are the Guyang and Linhe formations, the favorable exploration areas are the Hangwu fault belt, Jixi uplift belt and the deep sag in the north. Key words: Hetao Basin, Linhe Depression, petroleum geological features, Cretaceous Guyang Formation, Paleogene Linhe Formation, source rock, reservoir, Hangwu fault