Abstract: Based on the practical data of geochemical characteristics of natural gas, oil and gas distribution, the combination of source beds and reservoirs, and natural gas generation simulating experiment in laboratory, etc, it is concluded that the natural gas of Ordovician resulted from thermal evolution (thermal degradation and cracking). The occurrence of oil and gas is strictly controlled by the degree of maturity of organic matter. According to the color alteration index of conodont, Ordovician of the basin is divided into mature zone (Low value zone, CAI≤2), highly mature zone (Middle value zone, CAI=3～4.5) and over-mature zone (high value zone, CAI=5～6). Since the basin is at the stage of high maturity and early over-maturity, the target of exploration within the basin is mainly natural gas. The most promising area for gas exploration is in the east of Sichuan.

摘要： 根据天然气的地球化学特征、油气分布特征、生储组合、室内成气模拟实验等实际资料,论证了奥陶系的天然气是属于热演化(降解-裂解)气。油气的产出,严格受有机质成熟阶段的制约。还应用牙形石色变指数将盆地内的奥陶系划分为成熟区(即CAI≤2的低值区)、高成熟区(即CAI为3～4.5的中值区)、过成熟区(即CAI为5～6的高值区)。盆地内已处于高成熟至过成熟早期阶段,因此勘探对象主要为天然气。但在川西北龙门山断褶带靠盆地一侧,可望钻获石油。最后,结合储集条件对勘探的有利地区进行了预测,认为应加强川东的高陡、高尖构造的勘探。