原油物性演化规律新发现及其对页岩油勘探的启示

针对烃源岩生成的原油物性随热演化如何变化的问题,本文基于对准噶尔盆地玛湖凹陷下二叠统风城组和吉木萨尔凹陷中二叠统芦草沟组下段源储紧邻自生自储页岩油物性、地化特征、成藏特征及原油物性与烃源岩热演化关系的分析,综合烃源岩生烃热模拟实验结果与国内外相关文献资料,首次确认了咸化湖相烃源岩生成的原油物性与烃源岩热演化程度之间的变化规律。认为页岩油源岩生成的原油密度和黏度具有随热演化程度增强先增加而后降低的规律,其中生油高峰附近生成的原油非烃相对含量、密度和黏度最高。该认识不仅是对已有的石油地质学中原油物性随热演化规律认识的进一步厘定和修正,而且对页岩油甜点段、甜点区的选择以及页岩油原位转化等都有极为重要和现实的指导作用。

A new discovery of physical property evolution of crude oil and insights into shale oil exploration

The Fengcheng Formation in Mahu sag and the Lower Lucaogou Formation in which crude oil is accumulated in the oil layers of closely interbedded source and reservoir combination with self- generated and self- contained model, are considered as case studies to discover the transformation law of crude oil physical properties with thermal evolution degree of source rock.The transition law of crude oil physical properties with increased thermal evolution degree is determined based on (i) the analysis of physical properties, organic geochemistry and enrichment characteristics of crude oil; (ii) the relationship between physical properties of crude oil and thermal evolution degree of source rock; and (iii) comprehensively considering thermal simulation experiment results of source rock and domestic and foreign relevant literature materials. The density and viscosity of crude oil from a source rock has the characteristic of first increasing and then decreasing with increasing thermal maturity, with the highest value at the oil peak depth. This understanding is not only a further clarification and revision of the existing understanding of the evolution law of crude oil physical properties with thermal evolution in petroleum geology, but also a very important and realistic guidance for the selection of sweet layer and sweet spot of shale oil and the in- situ transformation of shale oil.