摘要
裂缝脉体的碳/氧同位素和包裹体对于研究油气保存条件有着重要的指示意义。为了揭示中扬子地区寒武系页岩气保存条件的差异性,选取该区3口代表不同构造条件和含气性的井(YY1井、YD4井、ZD1井)作为主要的研究对象,基于裂缝脉体包裹体和方解石脉碳/氧同位素测试分析资料开展了对比研究。研究结果表明:①该区寒武系裂缝脉体包裹体主要有液烃包裹体、甲烷包裹体、气液两相包裹体、盐水包裹体4种类型,(液烃+甲烷)包裹体/(气液两相+盐水)包裹体比值与油包裹体丰度一样对油气成藏与保存具有重要的指示意义,YY1井以高演化液烃和甲烷包裹体为主,ZD1井以气液两相和盐水包裹体为主,YD4井介于二者之间,构造条件越复杂古流体中烃类的占比越低,水的比例越高;②Δ13C (δ13C围岩-δ13C方解石)值、Δ18O(δ18O围岩-δ18O方解石)值的变化范围与保存条件具有相关性,ZD1井的变化范围明显大于YY1井,高度封闭的页岩段Δ13C值、Δ18O值趋近于0,页岩内部跨层流体、外部流体侵入都会导致Δ13C值、Δ18O值变化;③包裹体及方解石脉碳/氧同位素指示YY1井裂缝导致页岩气向上散失,YD4井、ZD1井裂缝导致页岩气向下散失两种不同逸散类型;④初步建立了中扬子地区基于包裹体和方解石脉碳/氧同位素的寒武系页岩气保存条件评价指标。结论认为,中扬子地区寒武系页岩气保存条件由黄陵隆起向江南-雪峰隆起整体逐渐变差,黄陵隆起周缘的寒武系页岩是下一步页岩气勘探的重点。
C/O isotopes and inclusions in fracture veins are of great indicative significance to the study on oil and gas preservation conditions.In order to reveal the differences of shale gas preservation conditions in the Cambrian of Middle Yangtze area,this paper selects three wells(YY1,YD4 and ZD1)representing different structural conditions and gas bearing properties of this area as the main research objects to carry out comparative study based on the testing and analysis data of fracture vein inclusions and calcite vein C/O isotopes.And the following research results were obtained.First,the inclusions in the Cambrian fracture veins of this area are mainly classified into four types,including liquid hydrocarbon inclusions,methane inclusions,gas–liquid two-phase inclusions and brine inclusions,and like grains containing oil inclusions(GOI),the(liquid hydrocarbon+methane)inclusion/(gas–liquid two-phase+brine)inclusion ratio is of great indicative significance to hydrocarbon accumulation and preservation.Well YY1 is dominated by high-evolution liquid hydrocarbon and methane inclusions and Well ZD1 by gas–liquid two-phase and brine inclusions.And the ratio is moderate in Well YD4.The more complex the tectonic setting is,the lower the percentage of hydrocarbon in the paleofluid is and the higher the proportion of water is.Second,the preservation condition is correlated with the change range ofΔ^(13)C(δ^(13)C surrounding rock–δ^(13)C calcite)andΔ^(18)O(δ^(18)O surrounding rock–δ^(18)O calcite vein),which is much larger in Well ZD1 than that in Well YY1.TheΔ^(13)C andΔ^(18)O of highly sealed shale section approach to 0.The occurrence of layer-crossing fluid inside the shale and the intrusion of external fluid can lead to the change ofΔ13C andΔ^(18)O.Third,inclusions and calcite vein C/O isotopes indicate that there are two kinds of gas escape.The fractures in Well YY1 lead to the upward escape of shale gas and those in Wells YD4 and ZD1 lead to the downward escape.Fourth,the indicators for evaluating the
作者
刘安
周鹏
陈孝红
蔡全升
李海
苗凤彬
彭中勤
黄惠兰
LIU An;ZHOU Peng;CHEN Xiaohong;CAI Quansheng;LI Hai;MIAO Fengbin;PENG Zhongqin;HUANG Huilan(Wuhan Center of Geological Survey,China Geological Survey,Wuhan,Hubei 430205,China;Hubei Key Laboratory of Paleontology and Geological Environment Evolution,Wuhan,Hubei 430205,China)
出处
《天然气工业》
EI
CAS
CSCD
北大核心
2021年第2期47-55,共9页
Natural Gas Industry
基金
国家科技重大专项“中扬子海相高演化页岩气赋存机理与富集规律研究”(编号:2016ZX05034-001-002)
中国地质调查局地质调查项目“宜昌斜坡区页岩气有利区战略调查”(编号:DD20179615)
古生物与地质环境演化湖北省重点实验室开发研究基金项目“中扬子地区寒武系页岩印支期以来构造演化的古流体响应”(编号:PEL-202011)。
