The Impacts Of Igneous Rocks On Hydrocarbon Generating Mechanism Of Source Rocks Of Yangxin Sag, Huimin Depression

In recent years, many igneous reservoirs have been found successively in many basins in China. Production potentials of igneous reservoirs is huge, their accumulating conditions are unique, and have been hydrocarbon exploration key. However, the study on the source rocks forming, hydrocarbon-generating characteristics around the igneous rocks is relatively few. The study of mutual relations between igneous rocks and source rocks is very important to hydrocarbon exploration.This dissertation researches the relationships of the igneous rock forming and the tectonic movement by using petrochemistry. The types of igneous rocks of Yangxin sag, Humin depression, includes basalt, basaltic andesite and trachybasalt, and the igneous rocks had been formed under the background of continental rift environment. The petrochemistry characteristics is well correlation with the 4 transition period of the basin evolution. Namely, the Mesozoic-Kongdian Formation, Kongdian-the Fourth Member of Shahejie Formation, the Third-the Second Member of Shahejie Formation and Dongying-Guantao Formation depositional transition periods. The correlation showed that the tectonic movement controlled igneous rocks forming and its evolution. The petrochemistry characteristics is a better tracer to tectonic movement.The sequences of Yangxin sag were controlled by both tectonic movement and igneous rocks distribution. The sequences contain igneous rocks with volcanic sedimentary characteristics, and their main control factors include tectonic volcanism, sediment supply and lake level change and so on. Volcanic activity effected on accommodation space of the lake basin cannot be neglected, and volcanic cone distribution made accommodation space complicated. The evolution of accommodation space presents uniformity. Because igneous rocks filled rapidly, the difference of the system tract and sequence boundary with normal deposition formation is obvious. The main periods of volcanic activity reflected well correlation with the main pull periods of tectonic movement. The forming stages of Paleogene igneous rocks of Yangxin sag were consistent with the sequences evolution.Volcanic activity brought large quantity of CO2, volcanic minerals, transitional metals and nutriments. These factors caused aquatic organisms were prosperous than before any times and any other places, which leaded to the shales around igneous rocks being rich in organic carbon of the source rocks. The shales were basically excellent source rocks with high hydrocarbon potentials (TOC>5%).The hydrocarbon generating mechanisms of source rocks around igneous rocks were diversification. There are lots of hydrocarbon generating catalysts in volcanic activities environment, and they are transition metal, volcanic minerals (including peridot, zeolite), more sulfur elements, much hydrogen and methane gas, respectively. At the same times the magmas and thermal-waters brought heat to the source rocks, and caused organic matter in the source rocks mature and hydrocarbon-generating earlier.Under the action of catalysts and heats, hydrocarbon generating threshold of the source rocks in igneous rocks area is shallower about 400m than the western region of Yangxin sag-Wenjia subsag. The hydrocarbon generating model of the source rocks in igneous rocks region showed that there are three hydrocarbon generating peaks, ie one low mature oil peak and two mature oil peaks respectively.