渤海湾盆地渤中19-6凝析气田凝析油成熟度判定及成因意义

Maturity of condensate oil and its significance in analyzing the formation mechanism of condensate oil and gas in the Bozhong 19-6 gas condensate field,Bohai Bay basin

关于渤海湾盆地渤中19-6凝析气田凝析油成熟度存在成熟与高成熟两种截然不同观点,尚未达到统一定论。本文综合利用轻烃、饱和烃和芳烃成熟度参数对凝析油成熟度进行了综合判定,并深入分析了凝析油和天然气的成因关系及凝析气藏形成机制。结果表明:异庚烷值与庚烷值、T_(s)/(T_(s)+T_(m))与C_(29)Ts/(C_(29)Ts+C_(29)H)、甲基单金刚烷指数与甲基双金刚烷指数、甲基菲指数、二苯并噻吩类成熟度参数和TNR_(2)显示渤中19-6凝析气田凝析油处于成熟阶段。结合天然气成熟度和储层流体包裹体特征,可知渤中19-6凝析气田的原油成藏期早于天然气,随着晚期大量天然气的充注,油气会发生相控混溶作用形成含液态烃的气流体,当温度和压力达到混溶后烃类体系的露点以上,则形成凝析气藏。

There are two entirely different viewpoints about the maturity of condensate oil in the Bozhong 19-6 condensate field,Bohai Bay basin:mature and highly mature,which have not reached final conclusion.Maturity parameters of light hydrocarbon,saturated hydrocarbon and aromatics are used to comprehensively discriminate the maturity of condensate oil,and the genetic relationship between condensate oil and gas and the formation mechanism of condensate gas reservoir are analyzed.Maturity indexes including isoheptane index and heptane index,T_(s)/(T_(s)+T_(m))and C_(29)Ts/(C_(29)Ts+C_(29)H),methyl adamantane and methyl diamantane index,MPI,dibenzothiophenes index and TNR2 indicate that the condensate oil in Bozhong 19-6 gas condensate field is mature.According to the maturity of natural gas and the characteristics of reservoir fluid inclusions,the main condensate accumulation stage is prior to that of natural gas.With charging of vast natural gas in the late stage,the crude oil and natural gas will undergo phase-controlled miscibility to form gas fluid containing liquid hydrocarbons.When the temperature and pressure reach above the dew point of the miscible hydrocarbon system,the condensate gas reservoir will be formed.