油气微渗漏方式定量判别思考

Quantitative discrimination of hydrocarbon micro-seepage pattern

调研前人关于烃类微渗漏方式的研究成果,发现油气藏形成之后烃类微渗漏方式以微泡方式和水溶方式为主。通过建立等厚地层模型,提出微渗漏方式定量判别系数,基于一般地质规律假定相关参数进行计算,分析认为:(1)烃类微渗漏方式在地层中并不是一成不变的,因地质条件变化可相互转变;(2)烃类微渗漏方式总体以微泡方式为主,随地层变浅水溶方式所占比例逐渐增加,此2种方式是形成地表烃类异常的主要方式,而扩散作用只形成背景场;(3)直接盖层封盖能力、地层物性和垂向可动水含量是影响烃类微渗漏方式的重要因素。烃类微渗漏方式定量判别系数的提出,对烃类垂向微渗漏机制研究从定性走向定量意义重大,为油气化探地球化学场数值模拟、成因解释与评价奠定了基础。

Studies of hydrocarbon micro-seepage have indicated that,when reservoir has been formed,oil and gas mainly seep as micro-bubble or with water.Based on isopachous stratigraphic model,a quantitative discrimination coefficient of micro-seepage pattern has been proposed and calculated according to general geological theory.It has been concluded that,1） Due to the changes of geological conditions,the micro-seepage pattern of hydrocarbon in strata is also changing;2） Hydrocarbon usually seeps as micro-bubbles and transfers to water-soluble pattern as it comes closer to earth surface.The 2 pa-tterns result in hydrocarbon abnormality on earth surface while diffusion only forms background field;3） Sealing ability of direct seal,stratigraphic physical property and vertical movable water content are the key factors controlling hydrocarbon micro-seepage pattern.Proposal of the discrimination coefficient is significant for micro-seepage mechanism research.It also settled a foundation for numerical simulation,formation interpretation and evaluation of geochemical field in hydrocarbon chemical exploration.