冀中廊固凹陷火成岩对烃源岩及油气生成的影响

EFFECT OF IGNEOUS ROCKS ON SOURCE ROCKS AND HYDROCARBON GENERATION IN THE LANGGU SAG,CENTRAL HEBEI PROVINCE

对冀中廊固凹陷火成岩侵入段烃源岩有机地球化学分析数据进行研究可知,火成岩侵入对镜质体反射率、H/C原子比等影响明显,而对烃比值、氢指数等影响不大,同时并未造成有机质过度熟化,而只是使生油高峰和湿气带上限提前。可见,火成岩侵入并非只是对烃源岩和先存油气藏起破坏作用,其短期的烘烤作用会使有机质的成熟度迅速增加,从而相比正常演化阶段要有所提前,尤其对未熟—低熟阶段烃源岩,可加速其熟化。而且火成岩多层侵入可增大生烃阶段烃源岩的厚度,更有利于油气生成。

Organic geochemical data analysis is conducted on source rocks in intrusive igneous rock inter val in the Langgu Sag, Central Hebei Province. The results indicate that intrusion of igneous rocks has distinct effect on Ro and H/C atomic ratio and less effect on HC/TOC and IH, and it only shifts the oil generation peak and upper limit of wet gas belt to an earlier time instead of inducing overmaturation of organic matters. In this way, intrusion of igneous rocks does not damage source rocks or existing oil and gas reservoirs, but increases maturity of organic matters fast by means of short-term baking, and espe cially for those source rocks at immature--low maturity stage. Therefore, it is ahead of normal evolution stage. In addition, multiple intrusions of igneous rocks can thicken source rocks of hydrocarbon generation stage, which is more favorable for hydrocarbon generation.