基于生物诱导碳酸钙沉淀的土体固化研究进展

基于微生物或脲酶诱导碳酸钙沉淀（MICP/EICP）的土体固化技术是近年来岩土和地质工程领域的研究热点之一。在系统回顾基于生物诱导碳酸钙沉淀的土体固化技术发展历程的基础上,重点阐述了MICP/EICP固化机制、土体孔隙结构、菌液和脲酶性质、胶凝液性质和固化方式等方面对碳酸钙特性影响的研究进展。研究结果表明：土体孔隙越小,越不利于微生物或脲酶入渗,固化均匀性越差;土颗粒接触点越多,可为碳酸钙提供的沉积点位越多,碳酸钙与土颗粒间的黏结和桥接作用越强,固化效果越好;一定菌液或脲酶浓度或脲酶活性范围内,碳酸钙的生成速率和生成总量随浓度及活性的增大而增大,但过高的浓度或活性易导致碳酸钙生成速率过快,从而在土体注入端发生堵塞;低浓度胶凝液得到的碳酸钙晶体更小,在土体中的分布更均匀;采用合适的注浆饱和度可提高具有黏结作用的碳酸钙的占比;采用多层交替注入或单相低pH值注入可提高碳酸钙在试样中分布的均匀性。基于碳酸钙沉淀特性的影响因素,提高固化土体的均匀性,验证其耐久性,室内试验结果在现场尺度的适应性和改进方案应该成为以后研究的重点。     

Environmental setting and microstructure of subfossil lithified stromatolites associated with evaporites, Marion Lake, South Australia

A variety of finely laminated, subfossil, aragonitic stromatolites and oncolites occur on a regressive marginal flat surrounding Marion Lake, South Australia. These algal forms overlie a substrate of coarse, highly porous, moldic aragonitic limestone which passes progressively towards the take centre through a zone of interstatified aragonite and gypsum and ultimately to pure crystalline gypsum. All of these facies overlie Holocene marine carbonate bank sediments which unconformably overlie at least one upper Pleistocene marine unit. Detailed petrographic and stratigraphic studies, combined with comparative studies of related nearby lakes containing a variety of living aragonitic cryptalgalaminates, provide a model for development of the Holocene sedimentary sequence. Marion Lake last became inundated by the sea around 6500 years ago during the Holocene transgression, when a protected marine environment was initiated. Lateral sediment accretion sealed marine passes into the resulting lagoon system soon after sealvel stabilized, and a variety of gypsum and gypsum-carbonate-algal facies evolved. Pure gypsum was deposited in waters 2–3 m deep in the central basin area concurrently with formation of seasonally alternating gypsum and aragonite layers towards basin margins. Blue-green filamentous algae thrived in the shallower marginal areas and at least partly controlled carbonate deposition, which must have occurred during seasonal outflow of carbonate-rich ground water from the calcareous dune aquifer over denser gypsum-saturated waters. These systems eventually migrated towards the centre of the lake to produce the relationships preserved today. The fresher waters also leached the gypsum from the marginal gypsum-carbonate facies. Collapse due to gypsum dissolution, along with aragonite crystallization, combined to form a lake-marginal mega-polygonal facies. Teepee structures formed around polygon margins, with optimum conditions for stromatolite development occurring on the teepee crests. The actual stromatolites which occur around Marion Lake are strongly indurated and involve a variety of morphologies, the most common of which are laterally linked hemispheroids. Stacked hemispheroids and oncolites are also relatively common, along with irregular forms, many of which encrust a variety of substrate irregularities. Vertical relief of the stromatolites varies from centimetres to tens of centimetres and all forms are characterized by extremely fine internal interlaminations of alternate light and dark grey laminae which typically occur several per millimetre. The microstructure comprises micritic aragonite crystals with fibrous habit associated with organic matter, and occasional zones of abundant algal filament molds which are generally oriented normal to the laminae.     

桂林洞穴滴水与现代碳酸钙δ18O记录的环境意义--以桂林七星岩NO.15支洞为例

现代洞穴动态监测的一个先决条件就是为洞穴碳酸盐(CaCO₃)沉积物-石笋的各种替代指标的解译提供可靠的依据,充分利用现代碳酸盐(CaCO₃)沉积物的各种替代指标,并与现代器测气象资料进行相互对比、并用以校正,是精确或定量解释石笋气候替代指标的关键.
经对桂林七星岩15号支洞的5个滴水点进行了长达四个水文年(2008~2011年)的大气降水、洞穴滴水、现代碳酸盐沉积物的动态监测和研究,并探讨了洞穴滴水和现代碳酸盐(CaCO₃)的δ18O与降水δ18O的相关关系.研究表明,洞穴滴水和现代碳酸盐(CaCO₃)的年平均δ18O值非常接近降水的δ18O平均值,并具有与地表降水δ18O相同的变化趋势,反映了洞穴滴水和现代碳酸盐(CaCO₃)的δ18O主要来自大气降水的δ18O,即明显受控于降水的δ18O.在4个水文年中,现代洞穴次生化学碳酸盐(CaCO₃)沉积物的δ18O值与滴水的δ18O值记录的年内(或年际)变化或多年的变化趋势基本相同,表现出明显的四高峰(δ18O低值区)四低谷(δ18O高值区)的波动变化特征,具有明显的年际、季节性变化规律,显示具有雨热同季的特点.研究结果表明洞穴滴水和洞穴现代碳酸盐(CaCO₃)沉积物的δ18O可以记录当地或洞穴上方的气候变化信号,即现代碳酸盐(CaCO₃)沉积物的δ18O主要作为夏季风强度或降雨量的替代指标.     

喀斯特区域的水化学不稳定性——以黔中地区为例

黔中地区是岩溶作用发育的喀斯特区域.1993年秋和1994年春末采自该地区不同类型水样的水化学分析表明:碳酸盐岩裂隙泉水呈中偏碱性,为[C]Ca-Ⅱ型;秋季离子总量、HCO₃-及Ca2+浓度大于春季.裂隙泉水流经地表一定距离后,HCO₃-降低,pH及SO₄2-、Cl-、K+、Na+明显增高.黄果树的天星桥、水帘洞及落水潭三个部位河水的SO₄2-、Na+以及Fe3+、NO₃-等浓度的季节性变化也更加明显.春季因瀑布暴气,CO₂的逸出,钙华生成更强烈一些.红枫湖作为喀斯特区域地表水的汇集地,HCO₃-与SO₄2-的当量比值仅2.1～2.4;Ca2+与Mg2+比值上升为2.4～4.2,Cl-浓度较碳酸盐岩裂隙泉水增高1倍;Na+浓度增高一个数量级.说明流域内地表土层溶蚀及人为污染影响的增强.土层孔隙水属强矿化水,而湖水呈现过渡特征.碳酸盐沉淀作用、硫酸盐矿化作用及固氮氨化作用,导致水质组成的显着差异.     

Water chemistry and sedimentological observations in littlefield lake,michigan: Implications for lacustrine marl deposition

A combination of both water chemistry and sedimentological information was used to investigate the carbonate-producing mechanism in Littlefield Lake, a small lake located in Isabella County, central Michigan. Data on temperature, dissolved oxygen, pH, calcium carbonate (CaCO₃) saturation, alkalinity, calcium, and magnesium were obtained on a monthly basis over a 13-month period, with each parameter determined at 1m intervals over a depth range of 20m. The loss of dissolved carbon dioxide (CO₂) from warm surface waters during direct degassing, and to a lesser extent during photosynthetic uptake by lacustrine macrophytes and phytoplankton during the summer, results in massive precipitation of the low-magnesium calcite which predominates in all Littlefield Lake sedimentary facies However, despite the fact that carbonate precipitation in this rather typical temperate-region marl lake is directly related to, and may be driven by, seasonal variation in these physiochemical parameters, most calcite forms as encrustations around cyanophytic and chlorophytic macrophytes. Such relationships demonstrate that carbonate precipitation in marl lakes may result from complex interactions between both biochemical and physiochemical processes. As such, marl formation in this, and probably many other calcareous lake systems, can not be simply ascribed to one or the other of these two general mechanisms.     

碳酸盐岩有机质丰度测试新方法

常规有机碳测试中仅对残余固相进行测试而忽略了酸解液,而前人研究证实酸解液中含有一定量的有机质。为了准确定量碳酸盐岩样品的总有机碳(TOC),提出蒙脱石增稠元素分析的新方法。本次研究以配比标样(CaCO₃+SiO₂+有机质标样)作为研究对象,对配比标样进行传统有机碳测试以及酸解后利用蒙脱石增稠进行元素分析的新方法测试。结果显示加入有机质标样为小分子有机酸(盐)的配比标样的传统有机碳测试的相对误差为98.5%~99.6%,加入大分子有机质的配比标样传统有机碳测试的相对误差较小,为11.9%~48.1%。而酸解后蒙脱石增稠进行元素分析测试的方法中,总有机碳(TOC)的相对误差为0.76%~19.46%。不同有机碳浓度的配比标样的元素分析法测试结果的相对误差随着有机碳浓度的增大而减小。新有机碳测试方法中,由于除去无机碳后将残渣与酸解液混合均匀并增稠,避免了有机碳的流失,更能客观反映样品总有机碳(TOC)。     

Bioerosion and carbonate mud production on high-latitude shelves

Low-latitude carbonate muds often are composed either of entire units of skeletons (e.g., algal muds) or of precipitates, whereas high-latitude carbonate muds are bioerosional or result from maceration. Bioerosion at high latitudes is most intense in the photic zone, particularly down to 25 m depth. Shelly substrata may be crushed, bitten, drilled, bored or scraped. Clionid sponges, endolithic algae, acmaeid gastropods and regular echinoids are the most significant agents. Clionids produce distinctive facetted carbonate silt chips when boring, which have been described from both high- and low-latitudes. Faecal pellets break down to yield mud-sized carbonate particles that are more irregular than those produced by maceration. Exhumed infaunal bivalves are often preferred to epifaunal organisms as substrata. Bioerosion occurs very rapidly; shells may be totally infested with boring algae in three months. A “moth-eaten” appearance therefore does not denote a relict grain. Reliable rates of fine sediment production are not yet available.

The mud fraction of northwest European shelf sediment generally contains 10–20% CaCO₃, though an inshore and offshore belt with higher values may be identified. Some Holocene supratidal mud-flats exceed 50% CaCO₃. Much of the shelf represents a modern-day equivalent of the “calcareous shale” facies common in the geological record. Instances of synsedimentary cementation are not uncommon, particularly in association with heavily burrowed muds.     

Geochemical Evolution of Great Salt Lake, Utah, USA

The Great Salt Lake (GSL) of Utah, USA, is the largest saline lake in North America, and its brines are some of the most concentrated anywhere in the world. The lake occupies a closed basin system whose chemistry reflects solute inputs from the weathering of a diverse suite of rocks in its drainage basin. GSL is the remnant of a much larger lacustrine body, Lake Bonneville, and it has a long history of carbonate deposition. Inflow to the lake is from three major rivers that drain mountain ranges to the east and empty into the southern arm of the lake, from precipitation directly on the lake, and from minor groundwater inflow. Outflow is by evaporation. The greatest solute inputs are from calcium bicarbonate river waters mixed with sodium chloride-type springs and groundwaters. Prior to 1930 the lake concentration inversely tracked lake volume, which reflected climatic variation in the drainage, but since then salt precipitation and re-solution, primarily halite and mirabilite, have periodically modified lake-brine chemistry through density stratification and compositional differentiation. In addition, construction of a railway causeway has restricted circulation, nearly isolating the northern from the southern part of the lake, leading to halite precipitation in the north. These and other conditions have created brine differentiation, mixing, and fractional precipitation of salts as major factors in solute evolution. Pore fluids and diagenetic reactions have been identified as important sources and especially sinks for CaCO₃, Mg, and K in the lake, depending on the concentration gradient and clays.     

柴达木盆地察尔汗古湖贝壳堤剖面沉积地球化学与环境变化

通过对柴达木盆地察尔汗古湖贝壳堤剖面沉积物中总有机碳、有机质碳同位素及碳酸盐含量、碳氧同位素的分析, 并结合粒度数据, 将研究剖面所记录的古湖泊环境演化过程划分为5个阶段.其中254 (连续古湖泊沉积开始与第八层底部) ~210cm (距今39.7~35.8ka BP之间) 为湖泊发育期.210~185cm (距今35.8~33.6ka BP之间), 185~112cm (距今33.6~27.2ka BP之间) : TOC、CaCO₃含量较高、δ18 O值偏正, δ13 C_org偏负, Mz值较低, 反映了当时温度较高, 湖水水位较高; 而112~55cm (距今27.2~22.3ka BP之间) 和55~0cm (距今22.3~17.5ka BP之间) : TOC、CaCO₃含量较低、δ18 O值偏负, δ13 C_org偏正, Mz值较高, 表明了温度相对较低(但气候仍较温暖), 湖水水位较低, 湖泊处于退缩时期.其间分别在距今32.2~32.4ka BP、30.4~29.8ka BP和28.4~27.2ka BP出现了3次较大的退缩过程, 约22ka BP出现了一次气候突变.贝壳堤剖面揭示在39.7~18.5 14C ka BP之间柴达木盆地气候较温暖湿润, 形成高湖面.从18.2ka BP开始, 湖泊进入退缩阶段.到17.5ka BP快速形成盐壳, 高湖面持续历史结束.      

再论巴丹吉林沙漠湖泊水的补给来源、补给模式与高大沙山的形成机理

依据已有研究成果和最新调查资料, 在综述沙漠湖泊与高大沙山研究进展及存在问题的基础上, 深入探讨了巴丹吉林沙漠湖泊水的补给来源、补给模式及高大沙山的形成机理. 结果认为, 沙漠湖泊水和地下水的补给来源不是当地降水和周边雅布赖山-北大山的降水形成的地表洪水, 而是南部青藏高原(包括祁连山)现代大气降水、冰雪融水、高原湖水的远源补给. 补给模式为高原富含CO₂气体和CaCO₃的入渗水, 通过深大导水断裂通道形成的区域地下水流循环系统, 源源不断地自南向北运移到沙漠地带, 地下水在通过沙漠湖泊区弧形"叠瓦状"垂向导水构造断裂向上越流过程中被广泛分布的岩浆岩加热, 沿断层溢出地表形成湖泊群, 同时导致水中CO₂的释放和CaCO₃的沉积, 形成钙华体. 高大沙山的形成机理是深层地下热水向上越流补给了沙漠覆盖区, 在承压水头以下形成鼓丘状的沙漠地下水, 承压水头以上, 水蒸汽继续向上运移并被凝结在沙粒表面, 未被吸附凝结的热水蒸汽继续向上运移并被吸附在新沉积的沙粒表面, 形成湿砂层并接受更新的沙粒沉积, 如此反复循环, 则沙丘高度不断增加, 逐步形成高大的固定沙山.     

风化淋滤带地质新理论-CaCO3淀积深度理论

根据黄土高原第四纪古土壤和风化带的广泛调查,发现了CaCO₃ 等化学成分的不连续淀积、厚层及多层淀积等特殊地质现象,结合CaCO₃ 含量分析与入渗实验资料,建立了风化淋滤带CaCO₃ 淀积深度新理论。该理论表明,CaCO₃ 迁移到淀积深度所需时间很短,可以忽略时间因素对它的影响,能够作为研究风化淋滤带的许多地质问题的较可靠依据。当CaCO₃ 淀积深度小于古土壤发育带厚度时,可确定土壤已向风化壳转变 当Ca CO₃ 淀积深度大于古土壤层厚度时,可确定土壤为淋溶型、中酸性土壤 当同一风化剖面中或同一层古土壤下部出现两层、三层或厚度异常大的CaCO₃ 淀积层时,指示当时出现了两个或两个以上成壤期和相应的气候变化。     

Groundwater salinity in Greve, Denmark: determining the source from historical data

Elevated salinity in groundwater (over 250?mg/l chloride) in a fractured chalk aquifer in the municipality of Greve, Denmark, has been attributed to seawater intrusion from the Baltic Sea, resulting in the closure of a number of wells nearest to the coastline. However, a recent study in eastern Denmark shows that the salinity could also be from ancient connate pore waters. Historical chemistry data from bulk-water samples collected from wells have been used to determine the source. The sample data were studied with respect to their historical changes and temporal trends in chloride, carbonate, sulfate, sodium, potassium, magnesium, and calcium. Wells in the southern third of the municipality are relatively low in sodium and carbonate and high in chloride and calcium/magnesium, indicating waters undergoing saline intrusion. Wells in the northern two-thirds of the municipality are high in carbonate and sodium, but low in chloride and calcium/magnesium, indicating a freshening of the aquifer. This is confirmed by the temporal trends in chloride, where chloride levels in the northern wells remain constant, whereas in the south, chloride increases as abstraction continues. Therefore close monitoring for seawater intrusion should be conducted in the southern third of the municipality.     

西藏高原达则错湖泊铀富集特征

达则错位于班怒构造带的次级盆地中,湖水最深为36 m,平均深度为20.8 m。湖表水体矿化度17.27~20.27 g/L,平均为19.46 g/L,水化学类型为(CO₃+HCO₃)·SO₄-Na型,属弱度碳酸盐型咸水湖;在垂向上,由浅及深矿化度略有增加,水化学类型不变。湖表水体铀浓度264~324μg/L,平均铀浓度为286μg/L,8 m、18 m和28 m深度铀浓度平均值分别为288μg/L、290μg/L和300μg/L。湖底沉积物铀含量为2.31~4.08μg/g,平均铀含量为3.16μg/g,略高于我国东海大陆架海底沉积物的铀含量。达则错湖水的铀元素来自于周边岩体和地层,通过河水迁移到湖泊中。在河口混合带,铀酰离子部分吸附于悬浮物上,到湖区以碳酸铀酰的形式存在于水体中,沉淀于湖底的悬浮物铀含量没有明显增加。     

六盘山地区下白垩统六盘山群乃家河组核形石形成的环境意义

六盘山寺口子水库下白垩统六盘山群乃家河组中发育了核形石,通过对其外部核心及纹层特征,以及核形石地球化学组分的研究,认为研究区核形石主要产于水动力较强的动荡水环境中,对捕捉和粘附碳酸钙质点作用相当明显,藻类自身的钙化和原地微生物引发的沉淀作用也可能是核形石的成因。经分析得到核形石的Sr/Ba值为4.87,CaO的含量达到了48.18%,总体上,研究区核形石在盐度高、温度较高、气候炎热、蒸发量大的干旱环境条件下形成。这些环境与研究区在该时期受燕山运动的影响,地壳整体抬升,湖盆发生萎缩的构造背景是相符的。     

Constraints on water chemistry by chemical weathering in the Lake Qinghai catchment, northeastern Tibetan Plateau (China): clues from Sr and its isotopic geochemistry

Lake water, river water, and groundwater from the Lake Qinghai catchment in the northeastern Tibetan Plateau, China have been analyzed and the results demonstrate that the chemical components and ⁸⁷Sr/⁸⁶Sr ratios of the waters are strictly constrained by the age and rock types of the tributaries, especially for groundwater. Dissolved ions in the Lake Qinghai catchment are derived from carbonate weathering and part from silicate sources. The chemistry of Buha River water, the largest tributary within the catchment, underlain by the late Paleozoic marine limestone and sandstones, constrains carbonate-dominated compositions of the lake water, being buffered by the waters from the other tributaries and probably by groundwater. The variation of ⁸⁷Sr/⁸⁶Sr ratios with cation concentrations places constraint on the Sr-isotopic compositions of the main subcatchments surrounding Lake Qinghai. The relative significance of river-water sources from different tributaries (possibly groundwater as well) in controlling the Sr distribution in Lake Qinghai provides the potential to link the influence of hydrological processes to past biological and physical parameters in the lake. The potential role of groundwater input in the water budget and chemistry of the lake emphasizes the need to further understand hydrogeological processes within the Lake Qinghai system.     

The role of hydrothermal fluids in sedimentation in saline alkaline lakes: Evidence from Nasikie Engida,Kenya Rift Valley

Saline alkaline lakes that precipitate sodium carbonate evaporites are most common in volcanic terrains in semi‐arid environments. Processes that lead to trona precipitation are poorly understood compared to those in sulphate‐dominated and chloride‐dominated lake brines. Nasikie Engida (Little Magadi) in the southern Kenya Rift shows the initial stages of soda evaporite formation. This small shallow (<2 m deep; 7 km long) lake is recharged by alkaline hot springs and seasonal runoff but unlike neighbouring Lake Magadi is perennial. This study aims to understand modern sedimentary and geochemical processes in Nasikie Engida and to assess the importance of geothermal fluids in evaporite formation. Perennial hot‐spring inflow waters along the northern shoreline evaporate and become saturated with respect to nahcolite and trona, which precipitate in the southern part of the lake, up to 6 km from the hot springs. Nahcolite (NaHCO₃) forms bladed crystals that nucleate on the lake floor. Trona (Na₂CO₃·NaHCO₃·2H₂O) precipitates from more concentrated brines as rafts and as bottom‐nucleated shrubs of acicular crystals that coalesce laterally to form bedded trona. Many processes modify the fluid composition as it evolves. Silica is removed as gels and by early diagenetic reactions and diatoms. Sulphate is depleted by bacterial reduction. Potassium and chloride, of moderate concentration, remain conservative in the brine. Clastic sedimentation is relatively minor because of the predominant hydrothermal inflow. Nahcolite precipitates when and where pCO₂ is high, notably near sublacustrine spring discharge. Results from Nasikie Engida show that hot spring discharge has maintained the lake for at least 2 kyr, and that the evaporite formation is strongly influenced by local discharge of carbon dioxide. Brine evolution and evaporite deposition at Nasikie Engida help to explain conditions under which ancient sodium carbonate evaporites formed, including those in other East African rift basins, the Eocene Green River Formation (western USA), and elsewhere.     

Marine-like potash evaporite formation on a continental playa: case study from Chott el Djerid, southern Tunisia

An exceptional flood in January 1990 led to the formation of a large ephemeral lake on the Chott el Djerid, a salt playa in southern Tunisia. Repeated observations made during 1990 show that the ephemeral lake underwent four evolutionary stages: (1) initial flooding, (2) evaporative concentration of lake waters, (3) the movement of concentrated brine pools over the playa surface as a result of wind action, and (4) total desiccation of the lake by September 1990. During all four stages the brine chemistry of the lake was monitored. Water inflow into the Chott el Djerid basin was found to have a consistent Ca-SO₄-Cl-rich and HCO₃-CO₃-poor chemistry, reflecting the recycling of homogeneous assemblages of Cretaceous, Mio—Pliocene and Quaternary evaporites within the catchment. As the ephemeral lake shrank, these waters produced an Na-Mg-K-Cl-SO₄ brine which was similar to modern sea water. Mineral saturation data show that, during the desiccation of the lake, saturation with respect to both gypsum and halite was achieved and that the most concentrated brines were ultimately saturated with respect to potash phases. After the desiccation of the lake the main mineral phases found on the Chott included gypsum and halite. In addition, ephemeral deposits of carnallite (observed as carnallitite,3KMgCl_3·6H₂0 + NaCl) were found. This assemblage is that which would be expected to form if the waters had undergone salt norm evaporation at 1 bar pressure at 25°C (SNORM) in the evaporation model proposed by Jones and Bodine (1987). The nature of both the brine chemistry and evaporite mineralogy provides a new and rare example of marine-like potash-bearing evaporites being formed in a contemporary continental playa.     

准噶尔盆地玛湖凹陷下二叠统风城组含碱层段韵律特征及成因*

准噶尔盆地玛湖凹陷早二叠世风城组沉积时期为典型的碳酸盐型咸化湖盆,湖盆咸化过程中析出大量的碱矿(钠碳酸盐类矿物)。通过含碱层段主量元素、碳氧同位素分析,结合岩心宏观及微观矿物岩石特征,探讨了含碱层段韵律特征及形成机理。研究层段碱矿与沉凝灰岩互层,形成明暗相间的咸化韵律。浅色碱矿层质地较纯,主要为苏打和小苏打,主量元素表现为 Na₂O含量高,CaO、MgO、SiO₂和Al₂O₃含量低;暗色层段主要为含斑点状碳钠钙石的沉凝灰岩,主量元素表现为Na₂O含量低,CaO、MgO、SiO₂和Al₂O₃含量高。浅色碱矿层和暗色沉凝灰岩段碳氧同位素值均为正,表明其沉积水体具高盐度特征。浅色含碱层段具有更高的 δ¹⁸O 值,反映了碱矿层沉积时期强烈蒸发的气候条件。根据δ¹⁸O/δ¹³C值的波动将研究层段划分为炎热干旱和相对湿润的气候条件,并据此解释不同韵律层盐类矿物形成机理。暗色的沉凝灰岩沉积代表地表流水注入量大于蒸发量,沉凝灰岩中盐类矿物含量少或者呈斑点状从颗粒间的卤水中析出;随着蒸发量的增高以及古气候由温暖潮湿转变为干旱炎热,地表流水注入量急剧减少,强烈蒸发控制了碱矿的沉积,形成浅色质地较纯的碱矿层。气候的频繁交替形成了风二段碱矿与沉凝灰岩频繁互层的特征。     

济阳坳陷阳信-花沟-平南地区CO2气藏的储层和盖层

济阳坳陷是渤海湾盆地的一个次级构造单元,其中部阳信-花沟-平南地区是主要的二氧化碳 (CO₂ )气藏产出区。该地区CO₂ 气藏的储层主要有下古生界海相碳酸盐岩、下第三系湖相碳酸盐岩和三角洲相砂岩、以及上第三系河流相砂岩。下古生界碳酸盐岩储层分布于其北部潜山带,储集空间以构造裂缝和溶蚀孔隙为主。下第三系湖相碳酸盐岩储层分布于平方王地区的沙四和沙一段。下第三系三角洲相砂岩储层主要发育于高青-平南、林樊家和阳信等地的沙河街组。上第三系河流相砂岩储层分布十分广泛,但总体来讲,其北部地层砂泥比 (5 0 %～ 70 % )较高,砂岩单层厚度 (2 0～ 40m)大,孔隙度大,渗透率高;而南部地层砂泥比小,砂岩单层厚度薄,孔隙度小,渗透率低。研究区CO₂ 气藏的盖层以泥质岩类为主,致密砾岩次之。它们均为有效盖层。沙三段、沙一段、馆陶组上部至明化镇组下部泥质岩集中段是CO₂ 气藏最重要的三大区域盖层。沙四段致密砂砾岩盖层主要分布于八里泊残丘潜山的顶部,构成潜山圈团的盖层,其渗透性很低。与烃类甲烷气藏相比,两者的储层类型基本相同,但对于盖层而言,由于CO₂气分子半径较烃类甲烷气分子半径大,因而CO₂ 气藏对盖层的要求比烃类甲烷气藏低。