海拉尔盆地乌尔逊凹陷与松辽盆地孤店CO2气田含片钠铝石砂岩的岩石学特征

海拉尔盆地乌尔逊凹陷南屯组与松辽盆地孤店CO₂气田泉头组发育大量含片钠铝石砂岩。通过偏光显微镜、扫描电镜、茜素红-S染色、X射线衍射、电子探针与INCA能谱分析等,对含片钠铝石砂岩的骨架碎屑组分、胶结物与自生矿物、成岩共生序列等岩石学特征进行了系统研究。研究表明,含片钠铝石砂岩的岩石类型为长石砂岩和岩屑长石砂岩,粒度以细粒、细-中粒为主,分选差-中等。砂岩中胶结物主要为次生加大石英、自生石英、片钠铝石、铁白云石和粘土矿物。其中,片钠铝石最高可达砂岩总体积的22％在砂岩中或以放射状、束状、菊花状、杂乱毛发状、毛球状、板状等集合体充填孔隙,或呈束状和板状交代长石和岩屑。电子探针与INCA能谱综合分析表明,片钠铝石主要由Na、Al、O、C等组成。在含片钠铝石砂岩中,成岩共生序列依次为粘土矿物包壳-次生加大石英、自生石英、自生高岭石-油气充注-CO₂充注-片钠铝石-铁白云石。其中,CO₂注入前形成的自生矿物组合主要为次生加大石英、自生石英和自生高岭石,CO₂注入后形成的自生矿物组合主要为片钠铝石和铁白云石。     

自生片钠铝石的碳氧同位素特征及其成因意义

自生片钠铝石的碳氧同位素特征可以为片钠铝石的成因研究提供重要的地球化学依据。以海拉尔盆地乌尔逊凹陷和松辽盆地孤店构造片钠铝石碳氧同位素分析为基础，结合国内外已报道的自生片钠铝石的碳氧同位素数据，对自生片钠铝石的碳氧同位素特征及其成因意义进行了探讨。研究表明，海拉尔盆地乌尔逊凹陷和松辽盆地南部孤店CO2气田砂岩中片钠铝石的δ13C范围分别为–5.3‰～–1.5‰（PDB）、–1.9‰～+0.3‰（PDB），均分布于含无机碳物质δ13C分布区间（－9.0‰～＋2.7‰）内。计算出的海拉尔盆地和松辽盆地与片钠铝石平衡的CO2气碳同位素分布范围分别为－10.7～－7.0‰（PDB）、－8.7～－6.9‰（PDB），表明片钠铝石绝大部分形成于无机CO2背景。实际地质观察中形成片钠铝石的CO2绝大多数为岩浆脱气来源，岩浆成因片钠铝石碳同位素分布范围为－5.5～＋4.5‰（PDB）。海拉尔盆地和松辽盆地的片钠铝石是岩浆成因CO2气运移、聚集的特征矿物。计算出的海拉尔盆地和松辽盆地片钠铝石沉淀时介质水的δ18O值范围为-14.3～-9.4‰（SMOW），表现为轻同位素的特点，表明片钠铝石形成时地层水为大气降水。计算出的海拉尔盆地片钠铝石同位素为52.7～93.6℃，与样品所在深度处的古地温范围（65.4～87.6℃）基本吻合。     

Comparative studies on carbon origin of dawsonite between Hailaer Basin in China and Bowen-Gunnedah-Sydney basin system in Australia

Dawsonite, NaAlCO3(OH)2, is widespread as a cement, replacement and cavity filling in Hailaer Basin in China and Bowen-Gunnedah-Sydney (BGS) basin system in Australia. The origin of dawsonite is emphatically contrasted and analyzed through stable isotopic composition. Dawsonite δ13C values ranging from -4.0×10-3 to 4.1×10-3 are remarkably consistent through the BGS basin system. The calculated δ13C values of CO2 gas in isotopic equilibrium with dawsonite range from -11.3×10-3 to -4.6×10-3. These values indicate carbon of dawsonite came from inorganic CO2 gas accompanied by magmatic activity. In Hailaer Basin, the Dawsonite δ13C values ranging from -4.64×10-3 to 2.12×10-3 are also consistent. The calculated δ13C values of CO2 gas in isotopic equilibrium with dawsonite range from -11.82×10-3 to -5.11×10-3. According to the coincidence of dawsonite-bearing well and CO2 gas well with mantle source,lying along deep fracture within or adjacent to Yanshanian granite,it is concluded that CO2 gas forming dawsonite is derived from mantle related to magmatic process during the Yanshanian. A little biologic origin carbon owing to petroleum charging intervened when dawsonite formed.     

贝尔凹陷沉凝灰岩储层片钠铝石前体矿物研究

为拓展CO2封存的储层选取范围,研究CO2充注过的储层中矿物的赋存状态,通过薄片鉴定、扫描电镜分析、X--射线衍射分析及铸体图像分析等技术对贝尔凹陷含片钠铝石储层进行了系统研究。研究区发育片钠铝石的岩石类型为沉凝灰岩,储层深度范围为882.26~941.4 m,该类储层发育有2类9种储集空间类型,以次生孔隙为主,属于低孔低渗储层。岩石骨架碎屑颗粒石英、长石、岩屑均有不同程度溶蚀;自生矿物以片钠铝石、铁白云石和菱铁矿为主。片钠铝石主要以充填溶蚀孔隙或交代颗粒的形式产出。综合研究区岩相学、矿物含量和热力学分析结果,长石和片钠铝石的生成具有亲缘性,为片钠铝石的形成提供了必要的元素和生长空间。     

Mineralogy and major-element geochemistry of the lower Permian Greta Seam,Sydney Basin,Australia

The mineralogy of the high-volatile bituminous coals and associated strata from the Greta seam, Sydney Basin, Australia, has been evaluated in this study. Although the seam is not immediately overlain by marine strata, percolation of marine water into the original peat bed is indicated by the petrological, mineralogical and geochemical characteristics, which resemble those of coals with marine roof strata. The upper and lower sections of the seam have contrasting mineralogy. Pyrite typically comprises 40 to 56 wt% of the mineral assemblage in the marine-influenced upper part of the seam section. The lower part contains much less pyrite (typically <5 wt%, organic-free basis), and also relatively abundant dawsonite (up to 14 wt%, organic-free basis). The minerals within most coal plies are largely of authigenic origin. These include pyrite, siderite, clay minerals (mainly kaolinite and Na-rich mixed-layer illite/smectite), and quartz, most of which have a relatively early, syngenetic origin. Minor Ti-bearing minerals, anatase or rutile, and phosphate minerals, fluorapatite and goyazite, were probably also formed during early diagenesis. Other minerals have features that indicate late-stage precipitation. These include abundant cleat- and fracture-filling dawsonite, which may be the result of reactions between earlier-precipitated kaolinite and Na₂CO₃- or NaHCO₃-bearing fluids. Minor albite may also be epigenetic, possibly precipitated from the same Ca–Al bearing fluids that formed the dawsonite. The most abundant detrital minerals in the Greta coals are quartz, poorly ordered kaolinite, illite and mixed-layer illite/smectite (I/S). These occur mainly in the floor, roof and other epiclastic horizons of the seam, reflecting periods of greater clastic influx into those parts of the original peat-forming environment. Detrital minerals are rare in the coals away from the epiclastic horizons, probably owing to almost complete sediment bypassing in the depositional system. Alternatively, any detrital minerals that were originally present may have been leached from the peat bed by diagenetic or post-diagenetic processes.     

Geological note: Authigenic Sr‐Ba‐Ca carbonate minerals in coals of the Hunter Valley,New South Wales

Strontianite (SrCO₃), witherite (BaCO₃) and alstonite (CaBa[CO₃]₂) were among the range of epigenetic coal cleat/fracture carbonates identified within the Wittingham Coal Measures, Jerrys Plains Subgroup in the Hunter Valley. Three stages of diagenetic cement development, all related to basin evolution, are postulated. Material for the development of the various carbonates was derived from: basinal pore fluids, surrounding rock and organic matrix as a result of diagenetic exchange, active mass transport or devolatilization of basement rocks during metamorphism, including plutonic intrusion.     

火山碎屑岩对CO2的矿物捕获能力

CO2矿物捕获是指将大气中排放的CO2气注入到地下深部的含水层、油气田等渗透性储层中,通过一系列物理、化学反应,最终将CO2气以碳酸盐矿物的形式“固结”在岩石中。火山碎屑岩具有铁、镁离子含量高且容易释放及分布广泛等特点,是有前途的矿物捕获岩石类型。塔木察格盆地塔南凹陷铜钵庙组火山碎屑岩中发育大量的片钠铝石特征矿物,进一步证实了火山碎屑岩的矿物捕获能力。在火山碎屑岩中,CO2注入之后形成的矿物有片钠铝石、铁方解石、铁白云石等碳酸盐矿物,碳酸盐总量高达30%,说明CO2矿物捕获的能力较大。     

海拉尔盆地乌尔逊凹陷含片钠铝石砂岩捕获CO_2总量的估算

为揭示CO2地质埋存过程中砂岩对于CO2以矿物形式的捕获能力,以海拉尔盆地乌尔逊凹陷下白垩统铜钵庙—南屯组含片钠铝石砂岩为研究对象,基于含片钠铝石砂岩的时空分布,结合片钠铝石的含量和分子式开展了砂岩以片钠铝石形式固存CO2总量的研究。研究表明,海拉尔盆地乌尔逊凹陷下白垩统铜钵庙—南屯组中片钠铝石资源总量约为81.9亿t,含片钠铝石砂岩捕获的CO2总量约为25.0亿t。     

片钠铝石的成因及其对CO2天然气运聚的指示意义

片钠铝石作为胶结物、自生矿物或脉体，不仅分布在海相白云岩、油页岩中，而且还广泛分布在陆源碎屑岩及煤系地层中。大量的实例及人工合成片钠铝石实验表明，片钠铝石的形成需要碳酸溶液或过量的CO2气，片钠铝石的分布往往与CO2天然气藏相伴生。CO2气的来源决定了片钠铝石具有无机和有机两大成因类型，其中，无机成因包括岩浆成因和碳酸盐热解成因。然而，不论源于有机成因CO2气还是无机成因CO2气，片钠铝石均可作为富CO2流体运移或聚集的“示踪矿物”，地质过程中片钠铝石的出现或富集表明该区曾存在大量CO2运移或聚集。     

松辽盆地南部红岗油田青山口组砂岩中片钠铝石的形成温度

主要以松辽盆地南部红岗油田富含片钠铝石砂岩的红143和红146井为研究对象,通过普通薄片鉴定、茜素红-S染色、扫描电镜、能谱分析、显微测温等分析方法,对研究区含片钠铝石砂岩的成岩共生序列,尤其是流体包裹体均一温度进行了详细的研究.红岗油田成岩共生序列为:黏土矿物→石英次生加大边→方解石→片钠铝石→铁白云石→石英愈合微裂...