渤海湾盆地廊固凹陷天然气成因类型及分布规律

发布时间：2018-03-24 03:11

  本文选题：天然气组分　切入点：同位素　出处：《天然气地球科学》2017年09期

【摘要】：基于天然气组分以及组分同位素分析结果,结合凹陷烃源岩有机地球化学特征与地质背景,对廊固凹陷天然气的成因类型及其分布规律进行了研究。结果表明,廊固凹陷浅层(1 900m)与中深层(1 900m)天然气的地球化学特征存在很大的差异,具有不同的成因类型。浅层天然气藏以次生型生物改造气藏为主,是热成因气的湿气部分遭受细菌降解而产生的次生生物气与残留热成因气(主要为甲烷)混合而成。其主要特征为:气体干燥系数大于95%,但重烃气含量较高(ΣC_(2~+)0.5%);甲烷稳定碳同位素组成较轻(δ~(13)C_1值分布在-60‰~-50‰之间);异构丁烷含量增加,丙烷含量明显减少;很多气样稳定碳同位素序列在丙烷处发生局部倒转。深层天然气主要为偏腐殖型热成因气,而且大多数天然气为干酪根初次裂解气。深层天然气以低—中等成熟度(RO值范围为0.5%~0.8%)为主,主要来自成熟度相当的沙三下亚段烃源岩;而曹家务、固安地区深度超过4 000m的4个气样以及别古庄地区奥陶系潜山气藏成熟度较大(RO值范围为1.1%~1.5%),来自深层的沙四段—孔店组烃源岩。廊固凹陷深层天然气的分布受控于烃源岩干酪根类型以及热成熟度,浅层天然气的分布则主要与沟通深部热成因油气的断裂活动强度有关。固安、柳泉、郎东等地区浅层是次生型生物改造气藏的主要分布区与有利勘探带,固安—旧州地区大兴断层深部的砾岩体以及别古庄地区的潜山是深层热成因天然气的有利勘探区带。
[Abstract]:Based on the results of natural gas composition and isotopic analysis, combined with the organic geochemical characteristics and geological background of hydrocarbon source rocks in the sag, the genetic types and distribution of natural gas in Langgu sag are studied. The geochemical characteristics of natural gas in Langgu sag are very different from those in middle and deep layers, and have different genetic types. The shallow gas reservoirs are mainly secondary biologically modified gas reservoirs. It is a mixture of secondary biogas and residual thermal gas (mainly methane) produced by bacterial degradation of the humid part of thermal gas. Its main characteristics are as follows: the coefficient of gas drying is greater than 95g, but the content of heavy hydrocarbon gas is high (危 C ~ (2) ~ (0. 5)); The stable carbon isotopic composition of methane is lighter (未 ~ (13) C _ (-1)) distributed in the range of -60 鈥，

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