摘要
辽河坳陷滩海东部地区葵探1井获得天然气重大突破,其侏罗系、古近系天然气的甲烷碳同位素组成(δ^(13)C_(1))差异大,确定天然气成因与气源岩对于评价天然气资源潜力及选择勘探目标具有重要意义。系统分析了滩海东部地区古近系东营组、沙河街组三段和侏罗系小东沟组3套含气层系的天然气组分、稳定碳同位素组成等地球化学特征,对天然气成因和来源进行探讨。滩海东部地区发育有机热成因气和无机成因气2种类型:(1)古近系东营组和沙三段天然气为煤型有机热成因气,成分以甲烷为主,干燥系数介于0.789~0.949,δ^(13)C_(1)值主要在-35‰左右。主要气源岩为盖州滩洼陷沙三中下亚段泥岩,R_(o)在0.77%~1.59%之间。中浅层东营组天然气成熟度显著高于同深度泥岩,表明天然气来源于深部地层;而深层沙河街组三段天然气成熟度与同深度泥岩差异不大,表明天然气以原地聚集为主。(2)侏罗系小东沟组天然气为无机成因气,干燥系数平均值为0.991,δ^(13)C_(1)值>-20‰;推测东营末期深大断裂大规模走滑活动沟通地壳深部与地幔,费托合成的无机天然气沿断裂带运聚成藏。盖州滩洼陷沙三段成熟烃源岩分布区与营口—佟二堡走滑断裂带是分别探索有机热成因型与无机成因型天然气的有利目标区带。
In 2022,a significant gas breakthrough was achieved in the key exploration well(Kuitan-1) located in the Kuihuadao structural belt of the eastern offshore,Liaohe Depression,with high-productivity gas flows in Dongying Formation,Shahejie Member 3,and Jurassic Xiaodonggou Formation.It is worth noting that there are significant differences in methane carbon isotope composition(δ^(13)C_(1)) between the Mesozoic and Cenozoic natural gas formations.Determining the origin of natural gas and its source rock is significant for assessing the potential of natural gas resources and selecting exploration targets.This paper systematically analyzes geochemical data such as the components and stable carbon isotope composition of natural gas samples from the three gas-bearing strata.The results indicate that there are organic thermogenic gas and inorganic gas in the eastern offshore:(1) The natural gas in the Dongying Formation and Shahejie Formation belongs to the coal-type organic thermogenic gas,mainly consisting of methane,the dryness coefficient is at the range of 0.789-0.949.δ^(13)C_(1) is mainly around -35‰.Natural gas originates from the mature mudstone in the middle and lower part of Shahejie Formation in Gaizhoutan sag,and accumulates during the late Dongying-Minghuazhen periods.According to the empirical formula,R_(o) of gas source rock ranges from 0.77% to 1.59%.There is a clear indication of migration effects for natural gas in the middle and shallow Dongying Formation,with clearly higher Roof gas source rock than the mudstone at the same depth.In the deep Shahejie Member 3,it accumulates in situ or with short distance migration,indicated by the similar or slightly higher Roof gas source rock than the mudstone at the same depth.(2)The natural gas in Jurassic Xiaodonggou Formation is of inorganic origin.It has an average dryness coefficient of 0.991 and is characterized by extremely heavy methane carbon isotope(δ^(13)C_(1)>-20‰).It's inferred that the natural gas originates from Fischer-Tropsch synthesis in the
作者
胡英杰
刘兴周
黄双泉
蔡国钢
王延山
李金有
杨光达
侯拓
张东伟
HU Yingjie;LIU Xingzhou;HUANG Shuangquan;CAI Guogang;WANG Yanshan;LI Jinyou;YANG Guangda;HOU Tuo;ZHANG Dongwei(Petro China Liaohe Oilfield Company)
出处
《海相油气地质》
CSCD
北大核心
2024年第1期81-89,共9页
Marine Origin Petroleum Geology
基金
中国石油油气与新能源分公司重大科技专项“辽河油田探区‘十四五’油气资源评价”(编号:2023YQX20104)
辽河油田重大科技专项“辽河坳陷深层生烃动力学与天然气资源潜力评价”(编号:2021KJZX-02-02)联合资助。
关键词
碳同位素
气体组分
热成因气
无机成因气
费托合成
滩海东部地区
辽河坳陷
carbon isotope
gas components
thermogenic gas
inorganic gas
Fischer-Tropsch synthesis
eastern off-shore
Liaohe Depression
