柴达木盆地中深层混积岩储层形成机制

通过岩心观测、普通薄片、铸体薄片、扫描电镜、电子探针和岩石物性等分析,系统阐述了柴达木盆地典型中深层(西北区南翼山构造E₃²-N₁)混积岩的岩石学、储集空间/物性和成岩作用等特征,在此基础上讨论了储层形成机制。结果表明,混积岩以(泥质)泥晶灰岩、钙质含量较高的砂岩和粉砂岩及其混积岩为主;储集空间以溶蚀改造的裂缝和粒间溶蚀孔隙为特征,物性总体表现为低孔-特低孔、超低渗-非渗透;有利于形成储层的成岩作用是溶蚀和构造裂缝作用;储层形成机制可归纳为"岩性是基础,裂缝是条件,溶蚀是关键"。这可为区域中深层混积岩储层,乃至陆相湖泊混合沉积储层的研究与油气勘探开发提供借鉴与参考。     

Amplitude Variation with Offset Responses Modeling Study of Walkaway Vertical Seismic Profile Data at CO2 Geological Storage Site, Ketzin, Germany

An important component of any CO2 sequestration project is seismic monitoring for tracking changes in subsurface physical properties, such as velocity and density. Different reservoirs have different amplitude variation with offset (AVO) responses, which can define underground conditions. In the present paper we investigate walkaway vertical seismic profile (VSP) AVO response to CO2 injection at the Ketzin site, the first European onshore CO2 sequestration pilot study dealing with research on geological storage of CO2. First, we performed rock physics analysis to evaluate the effect of injected CO2 on seismic velocity using the Biot-Gassmann equation. On the basis of this model, the seismic response for different CO2 injection saturation was studied using ray tracing modeling. We then created synthetic walkaway VSP data, which we then processed. In contrast, synthetic seismic traces were created from borehole data. Finally, we found that the amplitude of CO2 injected sand layer with different gas saturations were increased with the offset when compared with the original brine target layer. This is the typical class III AVO anomaly for gas sand layer. The AVO responses matched the synthetic seismic traces very well. Therefore, walkaway VSP AVO response can monitor CO2 distribution in the Ketzin area.     

江西武山花岗闪长斑岩中黑云母成分特征及其成岩成矿意义

江西武山花岗闪长斑岩与矽卡岩铜矿在成因上密切相关,通过对其中的黑云母进行的岩相学观察和详细的矿物化学分析来探讨黑云母的形成条件及其成岩成矿意义。电子探针分析结果表明,武山花岗闪长斑岩中的黑云母富镁贫铁低铝高钛,属镁质黑云母。其AlⅥ为0.03~0.19,w(ΣFeO)/w(ΣFeO+MgO)为0.531~0.567,w(MgO)为12.80%~14.06%,指示武山花岗闪长斑岩属壳幔混源的I型花岗岩。黑云母结晶的温度为720℃~750℃,logfO2为-11.6~-12.5,压力为86 MPa~103 MPa,对应的侵位深度为2.84 km~3.39 km,表明该岩体形成于相对高温较浅环境,具有较大成矿潜力,有利于武山铜矿的形成。     

Degradation of rock fracture asperities in unloading,reloading, and reversal

Among the constitutive models for rock fractures developed over the years, Barton's empirical model has been widely used. Although Barton's failure criterion predicts peak shear strength of rock fractures with acceptable precision, it has some limitations in estimating the peak shear displacement, post‐peak shear strength, dilation, and surface degradation. The first author modified Barton's original model in order to address these limitations. Barton proposed his model for degradation of fracture asperities in unloading, reloading, and shear displacement reversal based on just one cyclic direct shear test. In this study, a database of results of 18 cyclic direct shear tests available in the literature was collected and analyzed. Modifications were made to Barton's original model (in terms of fracture cyclic shearing) to make it consistent with the modified model proposed by the first author. Copyright © 2010 John Wiley & Sons, Ltd.     

Metamorphic veining and mass transfer in a chemically closed system: a case study in Alpine metabauxites (western Vanoise)

In western Vanoise (French Alps), karstic pockets of Triassic‐to‐Jurassic metabauxites embedded in carbonate rocks and containing several generations of metamorphic veins were studied. During blueschist facies metamorphism, a cumulative amount of ～13 vol% of water is inferred to have been produced locally by successive dehydration reactions, and part of this fluid remained in the bauxitic lenses during most of the metamorphic cycle. Field and geochemical evidence show that these rocks have been isolated from large‐scale fluid flow (closed‐system behaviour). It is proposed that the internally derived fluid has promoted the opening of fluid‐filled open spaces (as attested by the euhedral habits of vein minerals) and served as medium for mass transfer from rock to vein. Indeed, the vein infill is obviously the result of chemical interactions, at the millimetre‐to‐centimetre scale, between the rock minerals and the locally produced aqueous fluid. Two vein types can be distinguished based on mineralogical and textural features: (i) some veins are filled with newly formed products of either prograde (chloritoid) or retrograde (chlorite) metamorphic reactions; in this case, fluid‐filled open spaces seem to offer energetically favourable nucleation/growth sites; (ii) the second vein type is infilled with cookeite or pyrophyllite, that were present in the host rock prior to the vein formation. In this closed chemical system, the components for the vein infill minerals have been transferred from rock to vein through the fluid, in a dissolution–transport–precipitation process, possibly stress‐assisted. These different vein generations all contain Al‐rich mineral infills, suggesting that Al was a mobile element (cm scale) during metamorphism. In these HP rocks, fluid flow may have been restricted, and if so mass transfer occurred by diffusion in an almost stagnant fluid. Metamorphic veins can be seen as witnesses of fluid and mass redistribution that partly accommodate the rock deformation (lateral segregation).     

高温高压岩石流变仪的围压标定方法

高温高压岩石流变仪围压标定的主要方法为氯化盐类的部分熔融法和矿物相变法。利用氯化盐类进行压力标定时,不仅可以利用单一盐类,也可以使用多种盐类的混合物;常用的压力标定矿物相变及其适用温压范围如下:石英-柯石英,500~1200℃、2.5~3.2GPa;钠长石-硬玉+石英,600~1200℃、1.6~3.2GPa;铁橄榄石+石英-铁辉石,600~1200℃、1~1.7GPa;磷镁石-Mg3(PO4)2-Ⅱ,565~825℃、0.6~0.9GPa;方解石-文石,600~1200℃、0.5~2.5GPa。不同的标定方法具有不同的特征,文中将进行详细介绍。     

贵州中东部剩余重力异常与区域矿产分布关系

重点研究1:20万剩余重力异常,结合航磁、物性、地质等资料,初步圈定区内隐伏、半隐伏岩浆岩体,对研究与重力异常、岩体分布关系密切的矿产的时间、空间分布及其成因,有一定参考价值和指示意义。     

碎屑岩与火山岩混积岩系层序地层学研究初探——以准噶尔盆地西北缘佳木河组为例

准噶尔盆地西北缘前陆冲断带是剖析西准噶尔地区盆山耦合关系、沉积体系发育的关键地段。该区二叠系佳木河组为火山岩、火山碎屑岩、碎屑岩组成的混积地层。火山岩与碎屑岩组成的地层单元有广义上的成因联系,因为它们都属于史密斯地层,并均具有旋回特征。针对不同的岩性区:碎屑岩岩性区、火山岩与碎屑岩共存区、纯火山岩区,找出由于构造火山活动、相对湖平面变化等因素形成的可作为层序界面的不整合面。碎屑岩岩性区不整合面在地震剖面上主要表现为削蚀、底超、双向下超、顶超、下切谷等;共存区为同时发育火山岩与碎屑岩的削蚀带,不整合面类型较复杂;纯火山岩区表现为相对湖平面下降形成的削蚀不整合面。故可以通过地震、钻测井资料识别各类不整合面,并依据火山喷发方式、火山旋回、沉积旋回,按照不同对比原则进行经典层序地层学划分。     

溪洛渡水电站某危岩体稳定性及加固措施研究

在现场调查分析的基础上,提出了溪洛渡水电站某危岩体的两种可能失稳模式（剪切坠落或拉裂倾倒失稳）,进而建立了相应的稳定性计算极限平衡力学模型,而且对危岩体的变形和破坏特征进行了数值模拟分析,分析结果表明,危岩体抗拉裂倾倒稳定性较差,剪切坠落失稳的稳定性系数较高。在稳定性分析的基础上,计算出危岩体倾倒失稳时,安全系数为1.5时的锚固力,进而提出了危岩体加固方案：充填凹岩腔+填充裂隙+预应力锚索＋锚杆联合加固,数值模拟表明此加固方案效果良好。     

岩爆破坏过程能量释放的数值模拟

岩爆是地下岩石开挖中的一种工程灾害现象,是岩体结构发生破坏时,由于内部储存的弹性能释放并转换为动能而造成动力形式的破坏。岩爆破坏过程中的能量释放与岩体在应力峰值前后的应力-应变特性紧密相关。另外,施工中开挖速度引起的加载速率的变化也会对岩爆的产生有明显影响。以岩体全过程应力-应变曲线试验为基础分析岩爆破坏过程。分析中采用的模型考虑了岩石峰值后应力-应变特性及加载速率的影响。运用数值方法对岩石洞室的开挖过程进行了模拟,在模拟中对岩体破坏的发生及弹性能释放过程进行了分析。数值分析结果显示,岩体洞室开挖过程中岩石破坏由岩体表面向岩体内部发展,岩石的弹性能释放率也随着破坏的发展而不断增加。分析结果还显示,岩体破坏时的弹性能释放速率会随着开挖速率的提高而明显增加。