裂谷盆地的火山热液活动和油气生成

我国东部裂谷盆地主力烃源岩中均不同程度地发育有玄武岩和辉长岩等基性火成岩,并且伴有规模不等的热液活动。火山热液活动会给烃源岩带来热量,促使有机质快速生烃和异常成熟。玄武岩活动期间的热液作用为烃源岩提供了大量矿物质和养料,使周围泥质岩富含碳酸盐和有机质,可以形成优质烃源岩;热液活动向烃源岩提供了大量过渡金属元素,作者的实验证明了过渡金属对有机质生烃具有强烈的催化作用,使烃源岩在较低温度下生成较多数量的油气;火成岩周围的烃源岩可以提前进入生烃门限。

VOLCANIC AND THERMAL- WATER ACTIVITIES AND HYDROCARBON GENERATIONS IN THE RIFT BASINS, EASTERN CHINA

The basalts and gabbros, as well as thermal-waters, were distributed, more or less, in the hydrocarbon source rocks in the rift basins, Eastern China. Generally speaking, the magmas and thermal-waters brought heats to the source rocks, caused organic matter in the source rocks mature and hydrocarbon generating earlier. The authors recognized that the magmas and thermal-waters provided large quantity of CO₂, volcanic minerals, transitional metals and nutriments(including P and N)to the source rocks, which resulted in the shales around igneous rocks being rich in carbonate and organic carbon. The shales were basically excellent source rocks with high hydrocarbon potentials. The transitional metals and some volcanic minerals were active catalysts to hydrocarbon generation from the organic matter in the source rocks around the igneous rocks, which represented more oil and gas being generated at lower temperatures in burial of the source rocks and igneous rocks. Having conducted a series of thermal stimulations of hydrocarbon generation of oil shales from the Dongying Depression with Ni and Co catalysts, it was put forward that the hydrocarbon generation from the oil shales began at 120℃, about 100℃ lower than the generation without the catalysts, and the quantity of the generated hydrocarbons were several times more than those without catalysts in stimulating temperature being 200～280℃. Based on what mentioned above, it was concluded that the source rocks around basalts or gabbros generated much more oil and gas at much lower burial depths in a rift basin comparing with that ones far away from igneous rocks or not companying with volcanic rocks and thermal-water activities.