摘要
桑托斯盆地Jupiter油气田油气藏中富含CO_2,气层与油层流体成分存在明显差异,油气藏相态及形成机理没有取得共识。采用四参数方框图法、流体组分三角图、φ_1值、Z_1以及Z_2等多参数法对Jupiter油气藏相态进行综合判识,认为Jupiter油气藏为带油环凝析气藏。油气藏中凝析油与原油具有相似的分子地球化学特征,Pr/Ph比值为1.58~1.88,C_(26)三环萜烷/C_(25)三环萜烷比值为1.15~1.22,甾烷以C_(27)甾烷占优势,藿烷/甾烷比值大于4,TPP比值大于0.5,全油碳同位素在-25‰左右。地球化学参数说明二者来源于白垩系Upper Barremian-Lower Aptian阶湖湘烃源岩。凝析油与原油具有相似的成熟度,均为生烃高峰的产物。烷烃气来自于Upper Barremian-Lower Aptian阶湖湘烃源岩,为生烃高峰——凝析油前期阶段的产物。CO_2为火山幔源型CO_2,大量CO_2后期注入形成的蒸发分馏作用,对早期形成的油气藏进行改造,形成了现今带油环凝析气藏的面貌。地球化学参数证实了蒸发分馏作用的存在,无机CO_2的注入丰富了蒸发分馏作用理论。
The high CO_2 content and various fluid components in oil and gas columns of reservoirs of Jupiter oilfield in the Santos Basin is the main reason why there has not been a consensus on the phase and forming mechanisms of the reservoirs yet. Based on a four-parameter-block diagram,a ternary diagram of fluid component,and a multiple parameter method with φ_1,Z_1 and Z_2 values,we tried to understand the phase of reservoirs in Jupiter Oilfield. The result shows that the reservoirs are condensate reservoirs with oil rings. The condensate was found to share similar molecular characteristics with that of the crude oil in the reservoirs：Pr/Ph value between 1. 58 and 1. 88,C_（26）/C_（25） tricyclic terpane value ranging from 1. 15 to 1. 22,high abundance of C_（27） sterane relative to C_（29） sterane,hopane to sterane ratio value greater than 4 and TPP value greater than 0. 5,and carbon isotope value of whole oil at-25‰. All these geochemical parameters indicate that both the condensate and the oil be originated from the Cretaceous Upper Barremian-Lower Aptian lacustrine source rocks. Both the condensate and the crude oil have similar maturity and correspond to peak oil generation stage. The maturity of alkane gas,sourced from the Upper Barremian-Lower Aptian lacustrine source rocks,corresponds to the peak oil generation-early condensate forming stage. The CO2 is volcano-mantle type and its later influx transformed the reservoirs that formed at the early stage through evaporative fractionation,resulting in the present condensate reservoirs with oil rings. The evaporative fractionation is supported by geochemical parameters. The influx of inorganic CO2 added some new content to the theory of the evaporative fractionation.
出处
《石油与天然气地质》
EI
CAS
CSCD
北大核心
2017年第2期371-378,共8页
Oil & Gas Geology
基金
中国石化科技部项目(JP14008)
关键词
蒸发分馏
带油环凝析气藏
CO2
油气藏
白垩系
Jupiter油气田
桑托斯盆地
evaporative fractionation
condensate reservoir with oil ring
CO2
hydrocarbon accumulation
Cretaceous
Jupiter oilfield
Santos Basin
