Multiple Phases of Hydrocarbon Generation and Migration in the Ordovician Carbonate Reservoirs in the Tazhong Uplift

The Ordovician carbonate reservoirs in the Tazhong area, tarim basin, were formed in complex geological conditions, however, rich in hydrocarbon resources. It is of important significance to study the multi-stages of hydrocarbon generation and migration. This study integrates geological and geochemical methods to analyze the issues. The results indicated that the hydrocarbons in the Ordovician carbonate rocks of the Tazhong area were primarily derived from the Mid-Lower Cambrian and Mid-Upper Ordovician source rocks. The oil mainly came from the mix of the two source rocks and the gas from the oil cracking gas of the Mid-Lower Cambrian source rock. Hydrocarbons migrated into the Tazhong Uplift from the northern part of the Majiaer Depression through a series of injection points over four periods. There were a total of six injection points identified at the intersections of the NE trending faults and the NW trending flower strike faults. The hydrocarbons then migrated from the injection points into traps along regional trends from NW to SE and from NE to SW. There were four periods of hydrocarbon accumulation in the area, i.e. the Cambrian period-Ordovician period, the Silurian period-Devonian period, the Carboniferous period-Jurassic period and the Cretaceous period-Present.