岩浆侵入对油气地化特征的影响——以惠民凹陷为例

Influence of magmatic intrusion on oil and gas geochemical characteristics-case of Humin sag

通过对惠民凹陷临南洼陷夏38井沙三段独立的辉绿岩侵入体以及阳信洼陷东部多层辉绿岩体周围烃源岩可溶有机质的地球化学分析,总结了侵入岩异常热作用对周围烃源岩生成油气地化特征的影响规律。受侵入岩影响形成的原油烃类组成特征及生物标志化合物特征均与正常成熟原油不同,且不同成熟度参数变化规律也存在较大差异。当岩浆侵入、烃源岩埋藏较深时,侵入体厚度较大的岩体能使正构烷烃组成中轻组分增加,主峰明显前移。当岩浆侵入、烃源岩埋藏较浅,且处于低成熟阶段时,侵入岩因影响程度不同,烃源岩中的正构烷烃组成会呈明显前峰型、双峰型或后峰型。岩浆侵入时的热作用主要是短时的高温作用。这一认识有助于确定侵入岩区油气受异常热影响程度,判断岩浆侵入时周围烃源岩的埋藏和演化情况。

Based on the analysis of geochemical characteristics of soluble matter of hydrocarbon source rocks surrounding the single intrusive diabase in middle Es3 formation in Well Xia38 of Linnan low-lying, and the multilayered diabase in lower Es3 and upper Es4 formation in Yangxin low-lying, the influencing effect of intrusive rock's thermal anomaly on the geochemical characteristics of oil and gas from the surrounding source rocks is concluded. It is found that their hydrocarbon composition and biomarker characteristics are different from those of normal mature oil and gas, and there are also greater differences between the variations of different maturity parameter. This conclusion can be reliably used for the determination of thermal anomaly's influence on the maturity of oil and gas in the invasion area, the embedding and evolvement process of surrounding hydrocarbon source rocks during magma invasion, as well as the research of oil and gas accumulation.