流体压力对金刚烷类化合物形成和演化的影响

Currently, the exploration of oils and natural gases in deep reservoirs has become a hot topic in China. Due to the extraordinary endurance of thermal degradation and biodegradation, diamondoid indices are playing a special role in the petroleum study in deep reservoirs. However, the mechanism and the influence factors of its formation and evolution are not well understood, which usually affects the field application of diamondoid indices. In order to develop the application of diamondoid indices in deep petroleum systems which are often characterized by high temperature and high pressure, we plan to establish a thermal simulation method which is suitable to the high temperature and high pressure situation and can reveal the effect of fluid pressure. Based on this method, series of thermal simulation experiments of n-C26 alkane, crude oil, and different types of lower mature source rocks under different pressures will be carried out. Then, the possible influence of fluid pressure will be revealed by comparing the yield and composition of diamondoids in the thermal pyrolysates under different fluid pressures. What’s more, the relationship of EasyRo and diamondoid indices under different pressures will be identified, and the diamondoid indices will be adjusted corresponding to pressures. Finally, the revised indices will be applied in the typical petroleum reservoirs in Tarim Basin to re-evaluate the thermal maturity of crude oils and the extent of oil cracking, as well as to investigate the origin and the formation mechanism of the oils.

深层油气藏的勘探开发已经成为我国油气勘探开发的重点领域之一。基于金刚烷类化合物的强抗热降解和生物降解的特征，金刚烷指标在深部油气研究中有其独特的优势。然而，对金刚烷形成和演化的作用机制和影响因素尚不十分明确，往往影响其指标的实际应用。深部油气藏通常处于相对高温高压的环境，为更好地指导金刚烷指标在深部油气藏中的合理应用，本研究拟建立一套适用于高温高压条件的、能反映流体压力效应的热模拟实验方法，在此基础之上，开展不同压力下，模型化合物n-C26、正常原油以及不同类型低熟烃源岩的热裂解模拟实验，通过对裂解产物中金刚烷的含量、组成特征等的对比研究，揭示流体压力对金刚烷形成和演化特征的影响；建立不同压力条件下，EasyRo-金刚烷指标之间的联系，对已有的金刚烷指标进行压力修正；最后将经压力作用校正后的金刚烷指标应用于塔里木盆地典型油气藏的实例剖析，探讨金刚烷成熟度指标、原油裂解程度指标等的实际应用。

深层油气藏的勘探开发已经成为我国油气勘探开发的重点领域之一。基于金刚烷类化合物的强抗热降解和生物降解的特征，金刚烷指标在深部油气研究中有其独特的优势。然而，对金刚烷形成和演化的作用机制和影响因素尚不十分明确，往往影响其指标的实际应用。本研究在黄金管封闭体系模拟实验装置基础上，建立了能反映流体压力的恒温热模拟实验方法，通过开展50MPa、100MPa和150MPa三个外部压力下的模拟实验，初步认识到同等热演化程度下，流体压力增大会抑制金刚烷类化合物的生成，进而影响金刚烷类化合物的绝对产率，但对金刚烷类化合物组成影响不大，因此常用的金刚烷类化合物比值指标几乎不受影响。在这样一个前提下，在我国两个典型含油气盆地准噶尔盆地和珠江口盆地开展了金刚烷类化合物指标的实际应用研究，明确了金刚烷类化合物指标在原油来源判识和成熟度评价方面的应用前景，基本形成了一套“分类型、分阶段、多指标”的金刚烷指标应用体系；并利用多元数理统计方法建立了基于金刚烷的原油母质类型判识模型以及金刚烷参数与热成熟度（EasyRo%）之间的定量关系模型。