渤海湾盆地渤中坳陷气油比的控制因素及勘探意义  

Factors to control GOR and its exploration implications in Bozhong depression,Bohai Bay basin

作　　者：王飞宇[1] 李洋冰[2] 曾花森[1] 师玉雷[1] 

机构地区：[1]中国石油大学(北京)资源与信息学院油气成藏机理教育部重点实验室 [2]中海石油基地集团有限责任公司采油技术服务分公司渤海石油研究院

出　　处：《中国海上油气（工程）》2006年第5期289-296,共8页China Offshore Oil and Gas

基　　金：国家重点基础研究发展计划项目(2003CB214603)支持

摘　　要：渤中凹陷烃源灶具有机质类型好（主体为Ⅱ型和Ⅰ型）、成熟度高（主体处于过成熟阶段）的特点。已有资源评价的基本认识是渤中凹陷的生气量大于生油量，生成烃类的气油比约为1500m^3／t，前人由此而做出该凹陷应以产气为主的远景预测。深埋的Ⅰ型和Ⅱ型源岩灶并非高效的气源灶，其生气量不及Ⅲ型源岩灶。沉积盆地气油比的主要控制因素是源岩氢指数，Ⅰ型和Ⅱ型源岩至生油窗底界排油效率可高达80％～90％，由于生成的油绝大部分已排离源岩，在源岩进一步成熟过程中仅有少量天然气生成，生成的天然气也可能溶于油藏中。因此，即使渤中凹陷现今东营组和沙河街组源岩处于高一过成熟阶段，环渤中凹陷的油气发现仍应以液态烃为主。已有的油气产率图版主要基于封闭体系模拟实验，未虑及石油的排出，对Ⅰ型和Ⅱ型源岩生气量的评价明显过高，故不适用于天然气资源评价。对于现今处于高一过成熟的Ⅰ型和Ⅱ型源岩，需从开放体系高排油效率的理念出发，按生烃动力学和质量平衡的方法分析生排烃量在地质历史中的演化。对于主体为Ⅰ型和Ⅱ型源岩灶的油气系统或沉积盆地，只要源岩所生成的石油尚未经历高温裂解，即使源岩灶处于高一过成熟阶段，仍应以找油为主，而源岩处于凝析油一湿气阶段甚至干气阶段，并不意味着区域资源量构成以天然气为主导，也并不意味着勘探方向应以找气为主。The hydrocarbon kitchen in Bozhong de- pression, Bohai Bay Basin, is characterized by good quality of organic matter （mainly Type Ⅰ and Ⅱ ） and high maturity （mainly in over maturation）. The available data of resources evaluation in the depression has suggested that the gas generation is greater in output than the oil generation, with the generated hydrocarbon having a gas to oil ratio（GOR） about 1500 m^3/t, from which Bozhong depression was predicted as a gas-prone area by some authors. However, the deeper-buried kitchen of Type Ⅰ and Ⅱ organic matter is not effective as a gas kitchen, and its gas generation is lower than a similar kitchen of Type Ⅲ organic matter. A major factor to control GOR of hydrocarbon in a basin is the hydrocarbon index （HI） of source rocks. For Type Ⅰ and Ⅱ source rocks, about 80% -90% of generated oil may be expelled at the oil window base, and these source rocks would only generate minor gas if they are buried further, with the gas probably dissolved in oil pools. Therefore, the exploration discoveries in the depression are still predominated by liquid hydrocarbon, even if the source rocks in Shahejie and Dongying Formation are now in high-over maturation. The presented yield models of oil and gas are derived from experimental simulations of a closed system, and the gas generation of Type Ⅰ and Ⅱ source rocks is obviously overestimated due to no consideration of oil expulsion out of the source rocks in the models. Thus these models are not suitable to the evaluation of gas resources. For the presently high-over maturated source rocks of Type Ⅰ and Ⅱ , it is required to analyze the evolution in hydrocarbon generation and expulsion over a geological history by the hydrocarbon-generation kinetics and the mass balance method under consideration of a high efficiency of oil expulsion in an open system. In a petroleum system or a basin in which the source rocks are predominated by Type Ⅰ and Ⅱorganic matter, oil should be taken as the main exploratio

关 键 词：气油比 控制因素 生烃动力学 排油效率 油气资源评价 渤中坳陷 勘探意义 

分 类 号：P618.130.2[天文地球—矿床学]