吐鲁番坳陷侏罗系泥岩超压特征及其对油气成藏的控制

吐鲁番坳陷已发现油气藏主要分布于中侏罗统,上侏罗统、白垩系及第三系也有分布,为了查明该坳陷油气藏的分布与超压泥岩地层的关系,对泥岩地层超压特征进行了研究.结果表明,吐鲁番坳陷存在多套超压泥岩盖层,其中最稳定与最有利的区域封盖层是中侏罗统七克台组超压泥岩段.吐鲁番坳陷侏罗系及其以上的油气藏分布主要受超压泥岩盖层的控制,在没有超压泥岩段发育的地区,油气藏由于多期断裂的活动而遭受破坏.此外,油藏与气藏对超压泥岩盖层的依存度存在差别,超压泥岩段对油藏的封盖作用多表现为间接封堵,而对气藏与气顶油藏的封盖作用多表现为直接封堵.分析认为,在中国西部多旋回叠合盆地中,如果没有盐岩、膏岩存在,超压泥岩在油气成藏及油气藏的后期保存过程中具有很重要的作用.图5参13

Characteristics of Jurassic mudstone overpressure and its control on oil and gas accumulation in Turpan Depression

The reservoirs discovered in the Turpan depression are mainly distributed in the Middle Jurassic, some distributed in the Upper Jurassic, Cretaceous and Tertiary. The characteristics of the mudstone overpressure are studied to reveal the relationship between reservoir distribution and mudstone overpressure. There are several overpressure mudstone cap-rocks in the depression, of which the most steady and the best one is in the Middle Jurassic Qiketai Formation. The distribution of reservoirs in the Jurassic and above sequences is controlled dominantly by mudstone overpressure. In the regions without mudstone overpressure, reservoirs are often destroyed because of frequent fault activities. Reservoirs have different dependence on the overpressure mudstone sealing. Overpressure mudstone seals oil reservoirs indirectly, while it seals gas reservoirs and gas-cap reservoirs directly. For the areas without rock salt or gypsum in the multi-cycle basins in West China, mudstone overpressure will play an important role in the hydrocarbon accumulation and reservoir preservation.