高-过成熟油气区油源精细对比新指标研究

Oil-source correlation has important scientific significance and practical value for determining hydrocarbon source rocks, looking for exploration direction, identifying new oil and bearing bits, and predicting oil scale. It has formed a relatively complete theoretical framework and technical methods to effectively guide the exploration of the shallow oil and gas resources. Currently, Deep oil and gas is the hot spot of the current domestic and international exploration. However, the majority of conventional geochemical indicator parameters becomed very complex in the high evolution stages and thus losed the function of indicating the original biogenic features. Therefore looking for fine new index parameters for deep high-overmature oil-source correlation is imminent. On the basis of previous studies, experiments results preliminary show that, the carbon and hydrogen isotopic composition of pristane and phytane significant changes in the oil generation stage. However the hydrogen isotopic composition remain stable at higher mature stages. Therefore, the carbon and hydrogen isotopic composition may become higher evolutionary stage oil-source correlation indicators. The project intends is the the thermal simulation experiments for the pure standard compounds, precursors of the pristane and phytane, as well as different types of hydrocarbon source rock samples. It will establish the Pristane, phytane hydrocarbon chemical thermodynamic model of isotopic fractionation. On the basis of summing up the carbon and hydrogen isotopic compositions of pristane and phytane at different evolutionary stages, combined with the relationship between the isotopic composition and the sources, a set of hydrogen isotope correlation method applying to the high and overmature stages for deep oil and gas will be established.

油源对比对于烃源层、找油方向、新含油气层位的确定和油气规模的预测具有重要科学意义与实用价值，已形成较为完善的理论框架和技术方法，有效地指导了中浅层油气资源的勘探。目前，深层油气是国内外勘探热点，但大部分常规地球化学指标参数在高演化阶段均发生了复杂变化，从而失去了指示原始生源特征的功能，因此寻找深层高-过熟油源精细对比新指标迫在眉睫。在前人研究基础上，我们进行了探索实验，结果初步表明，姥鲛烷和植烷的碳氢同位素组成在生油阶段明显变化，但之后氢同位素组成趋于稳定，因此其同位素组成可能成为较高演化阶段油源对比指标。本项目拟对姥鲛烷、植烷的标准化合物、前驱物和不同类型烃源岩样品进行热模拟实验，建立姥鲛烷、植烷碳氢同位素分馏化学热力学模型，并在总结不同演化阶段姥鲛烷、植烷碳氢同位素组成规律的基础上，结合同位素组成与母质来源的关系，建立一套适用于深层高-过熟油气区油源精细对比的单体化合物氢同位素方法。

油源对比是油气地球化学的一个重要研究领域，旨在查明原油运移成藏过程、预测烃源灶和卫星油气藏位置，为制定油气田勘探开发规划提供依据，因而具有十分重要的理论意义与应用价值。经过几十年的勘探开发，盆地中浅层油气资源已不再是增储上产的重点，取得突破的希望在深层。然而，由于经历多期构造演化，深层烃源岩和原油大都成熟度较高，致使常规生物标志化合物失去了指示原始生源特征的功能，迫切需要寻找新的有效指标。本研究借鉴天然气气源对比最重要的方法——单体稳定同位素法，试图寻找碳或氢同位素相对稳定的液态烃化合物。. 无环类异戊二烯烷烃C20以下的化合物多数来源于叶绿素a的植基侧链，其热稳定性以及抗微生物侵蚀的能力均强于正构烷烃。但是，碳数少于姥鲛烷的无环类异戊二烯烷烃除了来自于生物前驱物以外，还可能由长链同系物转化而来，这就可能造成同位素组成的不确定性。然而，姥鲛烷和植烷则不同，除植醇外很难由其它前驱物转化而来。姥鲛烷和植烷的碳氢同位素组成主要受有机母质性质（原始生物类型）和沉积环境所制约，其同位素组成基本上应代表初始产物的特征。另外，由于姥鲛烷和植烷特殊的类异戊二烯结构，相比于正构烷烃，他们的同位素变化应该更小。所以，我们对姥鲛烷和植烷的碳氢同位素随热成熟度增加的变化特征做了系统的研究，而在研究过程中我们意外发现链烷烃向芳烃的转化过程，由于芳烃化合物也是原油和沉积有机质的重要组成部分，其分布特征也具有重要的油气地球化学指示意义，故我们对此转化过程以及芳烃的同位素特征也进行了研究。