生油增压定量模型及影响因素

A quantitative model for the overpressure caused by oil generation and its influential factors

在考虑Ⅰ型干酪根烃源岩生油过程中孔隙水和油的排出、氢指数对生油的影响、生油作用产生的超压对孔隙水压缩和干酪根的压实作用、压实使石油密度变化等因素的基础之上,建立了生油增压模型,并通过生油增压物理模拟实验验证生油增压成因机制和生油增压模型。生油增压物理模拟实验结果显示Ⅰ型干酪根烃源岩生油过程中在一定条件下可以产生强超压,而且实测生油增压值与生油增压模型计算结果可比,说明生油作用可以成为含油气盆地产生大规模超压的一种成因机制,也验证了生油增压模型可以用于定量评价烃源岩生油增压。Ⅰ型干酪根烃源岩生油增压受烃源岩成熟度、有机碳含量、氢指数和石油残留系数(α)等多种参数影响。生油增压模型参数敏感性分析结果表明烃源岩有机碳含量、氢指数和石油残留系数(α)这3个参数中以氢指数对生油增压的影响最小,石油残留系数(α)影响最大。在没有排烃之前,烃源岩生油过程中如果渗漏的油量达到生成石油总量的25%,则不能产生明显的超压,但在封闭条件较好的情况下,有机碳含量仅有0.5%的烃源岩生油作用也可以产生比较强的超压。

Oil generated overpressure model was constructed with consideration of the leakage of oil and water during the oil generation of the source rocks with type I kerogens,the effect of hydrogen index on oil generation,the compaction of water and kerogens due to the oil generated overpressure,the change of oil density during the compaction and oil expulsion.The physical simulation of overpressure caused by oil generation proves the overpressure mechanism of oil generation and overpressure model,which indicate the oil generation of the source rocks with type I kerogens can cause the strong overpressure and is one of the dominant overpressure mechanism in petroliferous basins.The excellent correlation between the measured overpressure during the physical simulation and the calculated values indicate that the oil generated overpressure model can be used to quantitative estimation of overpressure caused by oil generation.The oil generated overpressure is affected by the source rock maturity,TOC contents,hydrogen index,the oil residual coefficient（α） and so on.The sensitive analysis of the parameters in the overpressure model suggest that the oil residual coefficient（α） is the most sensitive to the overpressure caused by the oil generation among the source rock TOC contents,hydrogen index and oil residual coefficient（α）,the hydrogen index is the least sensitive.Overpressure can not generate before hydrocarbon expulsion if oil residual coefficient（α） is less 0.75,however,strong overpressure can appear if the source rock TOC contents is only 0.5% with a good pressure seal.