我国海域油气化探的基本特点

BASIC CHARACTERISTICS OF OIL AND GAS GEOCHEMICAL EXPLORATION IN THE SEA AREAS IN CHINA

根据长期生产与科研资料 ,总结了我国不同海域海底表层沉积物中酸解烃、物上气、荧光光谱、紫外吸收光谱、蚀变碳酸盐、热释汞、氦、金属微量元素及海水中溶解烃、苯、酚等指标含量的分布特征、变化规律及其与油气藏的关系 ,发现我国不同海区地球化学空间变化较大、差异明显。在纵向上由深到浅化探指标呈正向梯度变化 ,油气微运移的地球化学形迹明显。化探异常比较集中出现在凹陷周边 ,而隆起区化探异常较少 ,强度较弱。化探指标组合与特点表明 ,各海区以寻找轻质油与天然气为主。筛选出的适于海域油气化探的技术方法系列是 :综合烃类气体法 (包括吸附烃、游离烃、吸留烃、水溶烃 )和芳烃光谱法 ,在抑制干扰因素和进行定量校正后 ,它们是指示油气藏较灵敏的指标 ,而近海底海水化学成分连测技术是今后油气化探、开发的重要方面。

The study on seeking oil and gas reservoirs in sea areas in China by geochemical prospecting methods has been conducted for almost 30 a,and some primary results have been achieved.Based on the practical and scientific data obtained from the long period of study,the authors summarized the distribution characteristics and the content variation regularities of acid-extraction,head-space hydrocarbons,fluorescence spectrum,ultraviolet absorption spectrum,altered carbonate,heat-released mercury,helium and trace mental elements in the sea bottom sediments,as well as hydrocarbons,benzene and phenol dissolved in waters.The following knowledge has been obtained through the summarization of the relationship between these indicators and the underground reservoirs:①The geochemical distribution varies greatly in different sea areas.②The geochemical effect over oil and gas reservoirs is stronger in the shallow than in the deep.③Vertically,the geochemical indicators change with a positive gradient from the deep to the shallow,indicating significant oil and gas migration trace.④The geochemical anomalies tend to occur within the depression and their adjacent areas,and seldom occur in the uplift areas.⑤The analysis of the indicator combination characteristics shows that the light oil and nature are the exploration focus in various marine areas.The series of techniques selected for marine oil and gas geochemical exploration are for comprehensive hydrocarbon gases(including absorption hydrocarbon,occluded hydrocarbon,water-dissolved hydrocarbon)and aromatic hydrocarbons.While these indicators are sensitive to reservoirs after restraining the disturbance factors and quantitative correction,continuous detecting technique of the chemical composition of the water near sea bottom is the important method for oil and gas geochemical exploration that will develop later.Exploration practices have documented that geochemical prospecting is the direct and effective method for seeking oil and gas reservoirs in sea areas.