中国海相盆地油气保存条件主控因素与评价思路

中国海相盆地具有多旋回演化、盆-山结构复杂、稳定性差的特点,油气保存条件是制约油气勘探的关键因素。本文在对中国海相盆地构造改造特征和油气藏破坏方式分析的基础上,对影响油气保存条件的主控因素进行了总结,提出了海相多旋回强改造盆地油气保存条件评价的思路方法。中国海相盆地构造演化具有"五世同堂、同序异时"的特点,燕山中晚期和喜马拉雅期是影响油气保存的关键构造变革期。海相油气藏的破坏方式主要有断裂切割、抬升剥蚀、褶皱变动、深埋裂解、岩浆烘烤、流体冲洗、生物降解和长期扩散等8种主要方式。构造、盖层、热体制、流体活动和时间是控制保存环境及其动态演化的主控因素。中国海相盆地油气保存系统的评价思路为,以上述5种主控因素动态分析评价为基础,以地质结构和源-盖组合为依据划分评价单元,以源-盖动态演化,今、古流体系统演化和油气藏动态成藏过程研究为重点,动态地评价油气保存系统,进而优选有利的保存单元。

Major factors controlling hydrocarbon preservation condition in the marine basins of China and its evaluation ideas

The marine basins of China are characterized with multi-cycle evolution, complex structure of basin-mountains and poor stability. Hydrocarbon preservation condition is the key factor controlling hydrocarbon exploration. Based on the analyses of characteristics of tectonic reconstruction and destruction styles of hydrocarbon reservoirs in the Chinese marine basins, this paper concluded the major factors controlling hydrocarbon preservation condition, and proposed the evaluation ideas of hydrocarbon preservation condition for the multi-cyclical strongly-reconstructed marine basins. Tectonic evolution of marine basins of China has characteristics with "five stages of tectonic movement superimposed on the same basin, and same sequence of tectonic evolution with different critical timing points for each stage of tectonic movement". The Mid-Late Yanshanian and Himalayan are the critical periods of tectonic changes for influencing hydrocarbon preservation. Destruction styles of marine hydrocarbon reservoirs mainly include the cutting of faults, uplifting and erosion, fold alteration, deep-burial cracking, baking of magma, fluid washing, biodegradation, long-term diffusion and etc. The major factors controlling preservation condition and its dynamic evolution include tectonic activity, seal rock, thermal regime, fluid activity and time. The evaluation ideas of hydrocarbon preservation conditions in Chinese marine basins are that the classification of evaluation units is made based on the dynamic analysis and evaluation of above-mentioned five major factors, as well as geological structures and source-seal assemblages. Based on the study of dynamic evolution of source-seal layers, systematic evolution of present- and paleo-fluids, dynamic processes of hydrocarbon accumulation, hydrocarbon preservation systems are dynamically evaluated, and then, favorable persevered units are selected.