盐湖相含膏盐岩层系成烃与成藏效应及其机制

Dongpu Depression is a typical saline lacustrine during Palaeocene in the Bohai Bay Basin of eastern China, which is enriched in various oil and gases with partial of them bearing abnormal features such as relatively high abundance of H2S in gases associated with the oil in the north depression and unusually high concentrations of dibenzothiophenes in partial oils. These suggest complicated hydrocarbons generation and accumulation effects that we are unclear enough. In this application(project), we try to use ESI FT-ICR MS technique and compound specific isotope of carbon and sulfur, combined with conventional GC and GC/MS analysis and simulated experiment, 1) to investigate chemical composition and relative distribution of whole fractions including NSO’s compounds and carbon as well as sulfur isotope for single compound for the saline lacustrine oils and rock extracts in the depression, and then to try to establish a few of new salt lake facies identifying index; 2) to unravel genetic mechanisms of hydrocarbons generation by source rock at very low temperature and/or formation mechanisms for immature oils in the saline lacustrine basin; 3) to reveal the formation mechanisms of the relatively high abundances of H2S in the gases in the north Dongpu Depression and the oils characterized by high sulfur content and unusually high dibenothiophenes in some oils, and to determine which factor is the main factors controlling the oils: source rocks, microbial action and interreaction between oil/rock and mineral? The emphasis of the project will be put on the controlling and its geochemical significance of sulphate, Na2SO4 and NaCl on hydrocarbons generation of the source rocks in the Dongpu Depression. The aim of this study is to disclose some puzzling questions about hydrocarbons generation, preservation and secondary alteration in the reservoir of the Dongpu saline lacustrine oils. Two manuscripts about this work would be expected to be published in internal and international journals with a relatively high level.

渤海湾盆地东濮凹陷是我国典型的盐湖含油气凹陷，油气类型多样、异常油气发育，富硫体系成烃与成藏效应研究薄弱。本课题采用傅立叶变换离子回旋共振质谱（ESI FT-ICR MS）、单体碳/硫同位素等技术，以东濮凹陷富膏盐岩层系烃源岩、相关油气为主要研究对象，在揭示盐湖相油气、烃源岩特征基础上，结合模拟实验，建立含膏盐岩层系原油/烃源岩基于FT-ICR MS、包含NSO大分子的全馏分范围的化学组分与单体硫同位素的盐湖相标识指标；借助FT-ICR MS等技术揭示盐湖相烃源岩低温生烃、未熟油-低熟油成因机制；阐明异常油气（高硫、高芳香有机硫）与母源岩、微生物改造及有机-无机作用之间的关系及其机制；重点揭示盐湖相膏盐岩矿对烃源岩生烃及其产物的控制、地球化学意义。期待通过本项目研究，解析东濮凹陷盐湖相油气勘探中存在的科学难题。在国内外高水平杂志上发表SCI论文2篇。

渤海湾盆地东濮凹陷是我国典型的盐湖含油气凹陷，含膏盐岩层系成烃与成藏效应研究薄弱。采用傅立叶变换离子回旋共振质谱（ESI FT-ICR MS）、单体碳/硫同位素等技术，以东濮凹陷富膏盐岩层系烃源岩、相关油气为主要研究对象，揭示盐湖相油气、烃源岩的地质地球化学特征、含膏盐岩层系的成烃与成藏效应、盐湖相油气的成因机制。结果表明，盐湖相原油/烃源岩具有显著不同于淡水相的特征，包括相对低值Pr/Ph、相对高丰度伽玛蜡烷、升藿烷普遍“翘尾”、nC37和nC38优势相对于邻位烷烃的优势等、丰富的b-胡萝卜烷、角鲨烷、C33类异戊二烯、富C30-S1、C40-S1硫化物、“两段式”单体烃碳同位素等，建立了多项基于NSO化合物和硫同位素的生源、沉积环境与成熟度指标。确认S1类、O1S1类化合物相对含量、O1S/S1比值等可作为盐湖、淡水湖的识别指标。观察到不少NSO化合物保留有生物标示物的骨架特征，反映两者之间的成因联系，指示低熟油中某些组分的低温成因。全馏分范围化合物的对比表明，东濮盐湖相"低熟油"仍主要来自埋深>3000m的成熟烃源岩。模拟实验与实测表明，膏盐岩矿物可通过催化作用、高热导率属性显著地影响烃源岩热演化与生烃进程，改变生烃门限与生油窗范围。一方面，使烃源岩生烃门限上提；另一方面可降低烃源岩达到过成熟演化阶段的深度。建立了东濮凹陷无盐区、中等厚度膏盐区、厚层膏盐区三种烃源岩成烃演化模式。利用单体烃硫同位素和高分辨率质谱，识别出东濮凹陷多个构造带存在TSR改造作用。确认含膏盐岩显著控制油气的空间分布、油气藏的温压、储层质量与油气运聚，并通过TSR作用对油气的保存与天然气的生成产生了局部的影响。相关研究为东濮凹陷及类似的盐湖相油气成因与成藏机制研究、资源评价与油气勘探提供了重要依据。.