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1.
川西坳陷中段原、次生气藏天然气特征及运移机制探讨 总被引：1，自引：0，他引：1
天然气的烃类组分、氮气和二氧化碳含量、干燥系数大小均是较好的天然气运移地球化学指标,其纵向变化规律显示天然气纵向运移特征.通过川西坳陷中段千余个天然气地球化学参数的系统分析,对川西坳陷中段原、次生气藏天然气特征及运移机制进行探讨.川西坳陷中段天然气随着运移距离的增加氮气含量逐渐增大(0～9.63%),二氧化碳含量逐渐减小(1.94%～0);次生气藏天然气沿着运移方向甲烷含量(83.48%～99.86%)、干燥系数(0.83%～1.0O%)逐渐增大;而原生气藏天然气的变化趋势正好相反,甲烷含量(99.93%～85.06%)、干燥系数(1.00%～0.85%)逐渐减小.地层压力和区域构造应力场是川西坳陷中段天然气运移的主要驱动力.川西坳陷中段侏罗系次生气藏和三叠系原生气藏运移方式有着明显区别:上侏罗统天然气主要由下部须家河组天然气窜层渗流运移而来,断裂是其最重要的运移通道;中侏罗统部分气藏由须家河组气源沿高速运移通道运移而来,而部分气藏是通过下部气源以水溶相的方式运移聚集成藏;须四段天然气以扩散运移方式为主,反应该层段天然气成藏时储层已相对致密;须二段天然气则以渗流方式为主,断裂在其中起到了重要的作用. 相似文献
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川西坳陷中段上三叠统须家河组储层沥青地球化学特征及成因研究 总被引：1，自引：0，他引：1
川西坳陷上三叠统须二、须四段致密砂岩的溶蚀孔洞、裂缝及砂岩层理界面上分布大量的沥青,沥青的热演化程度极高,须二段达到干气阶段,须四段达到湿气一干气早期阶段;经过针对砂岩中层理界面及裂缝、溶孔洞中充填的沥青及泥岩层裂缝中充填沥青取样的有机地球化学指标分析后显示:沥青具有较低的H/C、O/C比,须二段沥青残余生烃能力极小,须四段沥青还具有较大的残余生烃潜力;须家河组须二、须四段沥青为马鞍塘-小塘子组与须二段海湾相油型烃源岩在生油窗期成的古油藏,在后来的高温条件下裂解成天然气后残留物;须二,须四的古油藏构成了川西坳陷上三叠统须家河组天然气重要的气源. 相似文献
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莺歌海盆地底辟带热流体突破的地层水化学证据 总被引：1，自引：2，他引：1
地层水化学特征往往反映出盆地流体的成因和演化信息。莺歌海盆地地层水样品分析表明地层水矿化度可划分3个带,即非底辟带、底辟带上方常压段和超压段。非底辟带地层水矿化度接近于正常海水,而超压带为具有较低矿化度的NaHCO_3型水,底辟带上方常压段地层水矿化度变化极大,与垂向断裂距离有关,越靠近垂向断裂的井往往具有更低的矿化度和更高的 HCO_3~-和 CO_3~(2-)离子浓度。在远离垂向断裂的底辟带侧翼或较浅地层(<1200m)孔隙水接近正常海水,以 MgCl_2型地层水为主:而在毗邻于垂向断裂的浅部储层具有明显低的矿化度,与超压带流体相似,也具有较高的 HCO_3~-和 CO_3~(2-)离子浓度这些观察结果反映垂向断裂为深部超压热流体突破的主通道,底辟带上方成为地层原生孔隙水(海水)与超压带内低矿化度热流体混合场所,地层水矿化度越低,说明来自深部超压热流体所占比例越大。不同压力地层中的水化学特征可以很好地用来识别流体运移路径和可能的水-岩反应。 相似文献
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随着勘探由常规油气向非常规油气的深入,致密砂岩气逐渐成为勘探热点。川西坳陷新场地区须二段、四段致密砂岩储层是须家河组主要的产气层。受沉积环境、埋深、成岩环境的影响,不同物源下储层砂岩矿物组成、成岩演化以及储集物性等方面存在显著差异。首先,结合前人研究成果,通过砂岩类型和岩屑类型特征分析研究区须二段、须四段的物源方向。其次,通过储层岩石学特征、物性特征、储集空间特征及储集层成岩作用类型探究物源对储层特征的影响。最后,分别讨论不同物源下研究区须二段、须四段储层特征的差异性,揭示物源对储层的控制作用。取得认识如下：（1）须二段主物源区是米仓山—大巴山,须四段主物源区是龙门山;（2）须二段,米仓山—大巴山物源较龙门山物源控制的储层压实作用及硅质胶结作用略强,绿泥石薄膜发育,碳酸盐胶结作用弱。须四段,龙门山物源较米仓山—大巴山物源控制的储层碳酸盐岩屑极大地提高了储层的抗压实能力,长石溶蚀作用显著,方解石胶结作用略弱;（3）龙门山物源体系下,须二段绿泥石胶结和长石溶蚀作用主要改变储层物性,碳酸盐胶结和硅质胶结作用是储层致密化的关键因素;须四段溶蚀作用和相对较弱的压实作用是储层孔隙发育的主要因素,碳... 相似文献
7.
川西地区须家河组异常压力演化与天然气成藏模式 总被引：17，自引：2，他引：15
川西地区须家河组发育异常高的流体压力, 组内构成了互层式的生、储、盖组合, 探讨异常高压背景下的天然气运移成藏特点及其规律具有重要意义.根据大量实测压力数据, 得出了川西地区异常压力在纵向和平面上的分布规律.以现今实测压力、压实研究和包裹体测试获得的古压力为约束条件, 应用所建立的异常压力数学模型恢复异常压力的演化历史. 研究发现, 地层压力的纵向分布可概括为南部地区的“两段式”和北部地区的“三段式”, 北部的超压幅度最大, 平面上超压中心位于梓潼凹陷.早侏罗世—古近纪须家河组内发育沉积型超压, 新近纪—现今则新增构造型超压.以流体压力的分布及其演化为主线, 结合其他主要成藏要素, 建立了3种典型的天然气成藏模式. 相似文献
8.
综合利用泥岩声波时差、实测地层压力和地震资料 ,分析了辽河盆地大民屯凹陷的地下流体压力场特征 .研究结果表明 :(1)本区泥岩压实类型可划分为正常压实 -常压型、单段欠压实 -弱超压型和双段欠压实 -强超压型三大类 ;(2 )油层压力梯度接近于 1,多属正常压力系统 ;(3)利用地震资料研究平、剖面压力场特征具有较高的可行性与可靠性 ;(4)现今剖面压力系统由浅部正常压力、中部弱超压和深部强超压 3个部分组成 ,断裂系统、不整合面和相互连通的孔隙系统及底辟构造组成了凹陷内流体纵、横向输导的复杂网络系统 ;(5 )规模较大断层两侧的剩余压力和压力系数具较明显的差异性 ,断层对压力的形成、演化与分布起着重要的控制作用 ;(6 )欠压实与烃类生成是本区超压形成的主导机制 相似文献
9.
川西坳陷中段上三叠统须二段气水分布特征及成因机理 总被引：1，自引：1，他引：0
川西坳陷深层上三叠统须家河组储层致密化严重,气水分布十分复杂,已经成为制约天然气勘探和开发的关键问题。在对须二段致密气藏地质特征、流体特征和气水分布特征研究的基础上,结合研究区实际地质条件,综合物理模拟实验的结果,揭示了该区复杂的气水分布成因机理。研究结果表明,川西坳陷须二段天然气主要为煤型裂解气,地层水型主要表现为CaCl2型,属于高封闭环境下的地层水。试气资料和测井解释结果表明,川西坳陷深层须二段主要以气层和含气层为主,局部井为气水同层和纯水层,地层水无成层性,水的分布表现出串珠状残留地层水的特点。孤立的地层水不受构造的控制,水的产出并不表现出上水下气或上气下水的特点,由于储层非均质性强,在深盆气形成过程中,气驱替水首先通过相对疏松的高孔高渗的储集空间,而对超致密砂体内已封存完好的水体则无力驱替,形成“残留地层水”,物理模拟实验结果也证实了这一点。 相似文献
10.
须家河组二段是川西坳陷中的区域气层。长期以来，地质分层采用岩石地层单位界面。这一界面的穿时性，造成了构造演化分析中的误差。笔者以钻井、测井和地震资料为主要研究对象，在引入地震反射“等时”约束条件的前提下，通过对须家河组长期基准面旋回层序及须二段中期基准面旋回层序的划分和对比，在建立高分辨率时间一地层格架的基础上，经过地震微相特征的仔细分析，确认须二段顶面属Ⅲ级整合界面。 相似文献
11.
东营凹陷牛庄洼陷沙河街组发育有超压系统,这对油气运移和聚集过程有着重要的影响。在对超压系统现今发育特征研究的基础上,本文运用约束下数值模拟方法对牛庄洼陷超压系统的演化规律进行研究,并探讨了超压系统的主要形成机制。牛庄洼陷在沙河街组四段、沙河街组三段的下亚段和中亚段存在着超压系统,最大压力系数可以达到1.8,最大剩余压力超过了20MPa。自沙三段上亚段沉积期开始,超压系统开始发育。到东营组沉积期末,超压系统经历了大约10Ma的泄压过程。自新近系馆陶组沉积期,超压系统再次迅速增压,逐渐接近现今发育状况。上覆地层沙三段上亚段高沉积速率导致了超压系统的形成和早期剩余压力的增加,而水热增压和烃类物质大量生成联合造成超压系统晚期迅速增压。超压系统演化规律揭示出在油气主要运移期研究区古异常流体压力的分布状况,这为进一步开展牛庄洼陷油气运移和聚集过程的动力学研究提供了理论依据。 相似文献
12.
B. Cesare 《Contributions to Mineralogy and Petrology》1995,122(1-2):25-33
Equilibrium C–O–H fluid speciation calculations predict that graphite will precipitate from initially graphite saturated
fluid inclusions during cooling and exhumation of metamorphic rocks. In the case that no mass is gained or lost by the inclusions,
the original X
O ratio [O/(O+H)] of the fluid phase must be maintained. Given this closed system constraint, the down-temperature progress
of graphite precipitation can easily be monitored as a function of the varible X
O, and produces some effects that are of significance to fluid inclusion studies: 1. Variation of the H2O : CO2 : CH4 relationship in the graphite-saturated COH fluid, namely increase of X
H2
O and decrease of the carbonic fraction; 2. Decrease of fluid density due to precipitation of graphite, which is denser than
the residual fluid; 3. Alteration of the CO2 : CH4 ratio of the fluid, depending on the initial O : H ratio of the fluid: for X
O>1/3, fluids increase their CO2 : CH4 ratio with decreasing temperature, and vice-versa. This implies that the CO2 : CH4 ratio measured at room T will not represent the trapping value, which is in any case closer to unity. As a consequence of density reduction, isochores
extrapolated from densities observed at room temperature do not pass through the pressure-temperature conditions at which
the inclusion was trapped, with pressure underestimates of up to 2 kbar. Actual P-T trapping conditions are located along the equilibrium “bulk isochore” (curve of constant-X
O, constant-volume) of the fluid. Alteration of the CO2 : CH4 ratio is a mechanism by which a CO2-rich or CH4-rich carbonic phase can be formed from aqueous fluids that are slightly off the neutral X
O=1/3 value. Subsequent segregation of this phase from the aqueous counterpart may account for the formation of pure CO2 and CH4 fluids in the upper crust.
Received: 15 March 1995 / Accepted: 1 June 1995 相似文献
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首次报道了扬子板块北缘镇巴地区中-晚三叠世界线黏土岩锂的超常富集,黏土岩产于关岭组(T2g)/须家河组(T3x)平行不整合界面,为古风化壳沉积物,Li2O品位0.08%～0.11%,最高达0.22%,超过了该类型矿产的边界品位(0.06%),界线黏土岩的岩石学特征、矿物组成及岩石成因亟待查明。本文通过XRD分析、TIMA分析以及详细的地球化学研究,查明了界线黏土岩的矿物组成,探讨了黏土岩形成的沉积环境及物质来源,提出了不整合面黏土岩类关键金属矿产的综合找矿方向。研究表明,镇巴地区T2/T3界线黏土岩主要由石英、伊利石、高岭石组成,并含有极少量绿泥石、蒙脱石和铝绿泥石。主量元素(SiO2、Al2O3、TFe2O3、TiO2)特征表明界线黏土岩属于铝土质泥岩,黏土岩CIA值(化学蚀变指数)为85～93,ICV值(成分变异指数)为0... 相似文献
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基于野外露头、岩心、薄片及样品实验测试等资料, 对四川盆地梓潼地区须家河组储集层裂缝特征与控制因素进行了精细分析与解释。须家河组致密砂岩储集层主要发育3种类型的裂缝, 分别为构造裂缝、成岩裂缝以及与异常流体高压有关的裂缝, 并以构造裂缝为主。裂缝走向主要为近东西向、近南北向和北西向, 平均密度0.56条/m, 多为层内发育。平面上, 沿老关庙—文兴场—柘坝场构造, 裂缝密度依次减小; 纵向上, 以须四段裂缝最为发育。有效裂缝比例在老关庙地区最低, 向北东至柘坝场构造呈带状递增趋势。该区储集层裂缝的分布主要受岩性、岩层厚度、构造部位及异常流体压力等因素控制, 其中断层对裂缝分布的控制作用最为显著。细粒级、薄层砂岩更容易产生裂缝, 断裂带附近与构造高部位也是该区裂缝发育的有利区域, 且断层对裂缝的控制作用远大于构造高部位的影响作用。此外, 异常流体高压的存在也有利于该区裂缝的发育, 尤其是张裂缝, 其密度在高压区明显增大; 异常高压也能导致早期闭合缝重新开启, 并且对裂缝中矿物的充填程度与溶蚀强度有重要的控制作用。 相似文献
15.
N. V. Chertkova A. E. Tsai N. L. Mironov V. D. Shcherbakov 《Moscow University Geology Bulletin》2010,65(1):39-48
Theoretical models and experimental data on the thermodynamic and rheological properties of basalts from the Apakhonchich
lava flow (Klyuchevskoi Volcano, Kamchatka) were invoked for plotting projections of water-containing and dry liquidus and
solidus curves on the P
s
-T plane. The P-T-X
H
2O conditions for the formation of basaltic magma and the degree of its differentiation were determined from data on melt inclusions.
The calculated apparent viscosity of the melt containing 10% crystals at 1100°C, 1 GPa, and 3 wt % water is 1.1 × 103 Pa s, and the density is 2.5 g/cm3. 相似文献
16.
XIE Zengye LI Jian LI Zhisheng GUO Jianying LI Jin ZHANG Lu DONG Caiyuan 《《地质学报》英文版》2017,91(5):1836-1854
The alternative development of coal-bearing hydrocarbon source rocks and low-porosity and low-permeability tight sandstone reservoirs of the Triassic Xujiahe Formation in the Sichuan Basin is favorable for near-source hydrocarbon accumulation. The natural gas composition of the Xujiahe Formation in the Sichuan Basin is dominated by hydrocarbon gases, of which the methane content is80.16%-98.67%. Typically, the C_2~+ content is larger than 5% in main wet gas. The dry gas is mainly distributed in the western and northern regions of the basin. The non-hydrocarbon gases mainly contain nitrogen, carbon dioxide, hydrogen, and helium, with a total content of 2%. The carbon isotope ranges of methane and its homologues in natural gas are: δ~(13)C_1 of-43.8‰ to-29.6‰, δ~(13)C_2 of-35.4‰ to-21.5‰, δ~(13)C_3 of-27.6‰ to-19.8‰,and δ~(13)C_4 of-27.7‰ to-18.8‰. δ~(13)C_3δ~(13)C_4 occurs in some natural gas with a low evolution degree; such gas is mainly coal-related gas from humic-type source rocks of the Xujiahe Formation. As for the natural gas, δ~2 H_(CH4) values ranged from-195‰ to-161‰,δ~2 H_(C2H6) values ranged from-154‰ to-120‰, and δ~2 H_(C3H8) values ranged from-151‰ to-108‰. The dry coefficient,δ~(13)C and δ~2 H_(CH4) are all positively correlated with the maturity of source rocks. The higher the maturity of source rocks is, the larger the natural gas dry coefficient is and the larger the δ~(13)C and δ~2 H_(CH_4) values are, indicative of the characteristic of near-source accumulation. The δ~2 H_(C2H6) value of natural gas is influenced by paleosalinity to a relatively large extent; the higher the paleosalinity is, the larger the δ~2 H_(C2H6) value is. The Pr/Ph value of the condensate oil ranged from 1.60 to 3.43, illustrating light oxidization-light reduction and partial-oxidization characteristics of the depositional environment of coal-bearing source rocks of the Xujiahe Formation. The natural gas light hydrocarbon(C_5-C_7) from the Xujiahe Formation presented two characteristics: the first was the relatively high aromatic hydrocarbon content(19%-32.1%), which reveals the characteristic of natural gas with humic substances of high-maturity; the second was the low content of aromatic hydrocarbon(0.4%-9.3%),reflecting water-washing during the accumulation of the natural gas. The reported research outcomes indicate a potential mechanism for natural gas accumulation in the Xujiahe Formation, which will further guide natural gas exploration in this region. 相似文献
17.
Evidence from mineral assemblages for infiltration of pelitic schists by aqueous fluids during metamorphism 总被引：1，自引：0，他引：1
Prograde mineral assemblages and compositions have been predicted for pelitic schist in the 10 component system Na2O–K2O–CaO–MnO–FeO–MgO–Al2O3–SiO2–CO2–H2O for three cases of prograde metamorphism and fluid-rock interaction: (1) increasing temperature (T) at constant pressure (P) and constant pore fluid volume (1%) without infiltration (no-infiltration case); (2) increasing T at constant P accompanied by sufficient fluid infiltration that fluid composition is at all times constant (large-flux case); and (3) increasing T at constantP accompanied by a timeintegrated fluid flux f 104 cm3
cm
2 (intermediate-flux case). Stable mineral assemblages and compositions were calculated by solving a system of non-linear equations that specify mass balance and chemical equilibrium between minerals and fluid. The model pelitic system includes quartz, muscovite, plagioclasc, chlorite, ankerite, siderite, biotite, garnet, staurolite, andalusite, kyanite, sillimanite, K-feldspar, and a coexisting, binary H2O–CO2 fluid. Specifically, prograde thermal metamorphism was modelled for Shaw's (1956) average low-grade pelite and for a moderate range of bulk rock compositions at P=3, 5, and 7 kb and initial fluids with Xco
2
o
=0.02–0.40. The model predicts a carbonate-bearing mineral assemblage for average pelite under chlorite zone conditions composed of quartz, muscovite, albite, chlorite, ankerite, and siderite. The mineral assemblages predicted for the noinfiltration case are unlike those typically observed in regional metamorphic terranes. Simulations of metamorphism for the large-flux and intermediate-flux cases, however, reproduce the sequence of mineral assemblages observed in normal Barrovian regional metamorphic terranes. These results suggest that regional metamorphism of pelitic schists is typically associated with infiltration of significant quantities of aqueous fluid. 相似文献
18.
Mineral equilibria modeling involving solid solution calculations has been combined with mineral assemblage information from
the alteration zones associated with gold mineralization to determine the T and X
CO2 conditions for the formation of the Magdala gold deposit at Stawell, Victoria, Australia. Economic gold mineralization is
primarily hosted within the stilpnomelane alteration zone of the Stawell Facies that is adjacent to the Magdala Basalt. Evolution
of the Magdala gold deposit involved at least three fluid infiltration events: (1) a CO2-bearing fluid during the D2 deformation event produced carbonate spots throughout the chlorite zone; (2) a CO2–S–K-bearing fluid, accompanied the D3–4ab deformation and produced a muscovite zone and siderite rims on ankerite; and (3) a CO2–K–S–Au-bearing fluid during the D4c deformation event produced the stilpnomelane zone of the Stawell Facies, the proximal and distal alteration zones within
the Magdala Basalt, and the main economic gold mineralization. Mineral equilibria modeling constrains the temperature of formation
of the Magdala deposit to T = 345–390°C at 3kbar, substantially lower than indicated by other previous classical thermobarometry methods. Furthermore,
this method has allowed the characterization of the mineralizing fluid and constrained its composition to X
CO2 < 0.08 at 3kbar. The timing and composition of the mineralizing fluids are similar to that of metamorphic fluid generated
from devolatilization of a greenstone pile with peak of metamorphism occurring earlier and at deeper levels in the crust. 相似文献
19.
The melting reaction: albite(solid)+ H2O(fluid) =albite-H2O(melt) has been determined in the presence of H2O–NaCl fluids at 5 and 9.2 kbar, and results compared with those obtained in presence of H2O–CO2 fluids. To a good approximation, albite melts congruently at 9 kbar, indicating that the melting temperature at constant
pressure is principally determined by water activity. At 5 kbar, the temperature (T)- mole fraction (X
(H2O) ) melting relations in the two systems are almost coincident. By contrast, H2O–NaCl mixing at 9 kbar is quite non-ideal; albite melts ∼70 °C higher in H2O–NaCl brines than in H2O–CO2 fluids for X
(H2O) =0.8 and ∼100 °C higher for X
(H2O) =0.5. The melting temperature of albite in H2O–NaCl fluids of X
(H2O)=0.8 is ∼100 °C higher than in pure water. The P–T curves for albite melting at constant H2O–NaCl show a temperature minimum at about 5 kbar. Water activities in H2O–NaCl fluids calculated from these results, from new experimental data on the dehydration of brucite in presence of H2O–NaCl fluid at 9 kbar, and from previously published experimental data, indicate a large decrease with increasing fluid pressure
at pressures up to 10 kbar. Aqueous brines with dissolved chloride salt contents comparable to those of real crustal fluids
provide a mechanism for reducing water activities, buffering and limiting crustal melting, and generating anhydrous mineral
assemblages during deep crustal metamorphism in the granulite facies and in subduction-related metamorphism. Low water activity
in high pressure-temperature metamorphic mineral assemblages is not necessarily a criterion of fluid absence or melting, but
may be due to the presence of low a
(H2O) brines.
Received: 17 March 1995/Accepted: 9 April 1996 相似文献
20.
Incipient charnockites represent granulite formation on a mesoscopic scale and have received considerable attention in understanding fluid processes in the deep crust.Here we report new petrological data from an incipient charnockite locality at Rajapalaiyam in the Madurai Block,southern India,and discuss the petrogenesis based on mineral phase equilibrium modeling and pseudosection analysis. Rajapalaiyam is a key locality in southern India from where diagnostic mineral assemblages for ultrahigh-temperature（UHT） metamorphism have been reported.Proximal to the UHT rocks are patches and lenses of charnockite（Kfs + Qtz + Pl + Bt + Opx + Grt + Ilm） occurring within Opx-free Grt-Bt gneiss（Kfs + Pl + Qtz + Bt + Grt + Ilm + Mt） which we report in this study.The application of mineral equilibrium modeling on the charnockitic assemblage in NCKFMASHTO system yields a p-T range of～820℃and～9 kbar.Modeling of the charnockite assemblage in the MnNCKFMASHTO system indicates a slight shift of the equilibrium condition toward lower p and T（～760℃and～7.5 kbar）. which is consistent with the results obtained from geothermobarometry（710—760℃,6.7—7.5 kbar）. but significantly lower than the peak temperatures（>1000℃） recorded from the UHT rocks in this locality,suggesting that charnockitization is a post-peak event.The modeling of T versus molar H2O content in the rock（M（H2O）） demonstrates that the Opx-bearing assemblage in charnockite and Opxfree assemblage in Grt-Bt gneiss are both stable at M（H2O） = 0.3 mol%-0.6 mol%.and there is no significant difference in water activity between the two domains.Our finding is in contrast to the previous petrogenetic model of incipient charnockite formation which envisages lowering of water activity and stabilization of orthopyroxene through breakdown of biotite by dehydration caused by the infiltration of CO2-rich fluid.T-XFe3+（= Fe2O3/（FeO + Fe2O3） in mole） pseudosections suggest that the oxidation condition of the rocks played a major role on the stability of orthopyroxene:Opx is stable at XFe3+ <0.03 in charnockite.while Opx-free assemblage in Grt-Bt gneiss is stabilized at XFe3+ >0.12.Such low oxygen fugacity conditions of XFe3+ <0.03 in the charnockite compared to Grt-Bt gneiss might be related to the infiltration of a reduced fluid（e.g.,H2O + CH4） during the retrograde stage. 相似文献