Pore water evolution in oilfield sandstones: constraints from oxygen isotope microanalyses of quartz cement

Oxygen isotope microanalyses of authigenic quartz, in combination with temperatures of quartz precipitation constrained by fluid inclusion microthermometry and burial history modelling, are employed to trace the origin and evolution of pore waters in three distinct reservoirs of the Brae Formation in the Miller and Kingfisher Fields (North Sea). Oxygen isotope ratios of quartz cements were measured in situ in nine sandstone thin sections with a Cameca ims-4f ion microprobe. In conjunction with quartz cement paragenesis in the reservoirs, constrained from textural and cathodoluminescence (CL) microscopy studies, pore water evolution was reconstructed from the time of deposition of the sandstones in the Upper Jurassic until the present.CL photomicrographs of quartz overgrowths in the Brae Formation sandstones show three cement zones (A, B and C) which can be related to different oxygen isotope compositions: (1) the earliest, and thinnest, zone A (homogeneous CL pattern with probable δ¹⁸O values between +23‰ and +26‰—direct measurements were not possible) precipitated in the sandstones at temperatures <60 °C; (2) the second zone B (complex CL pattern and directly measured δ¹⁸O values between +15‰ and +18‰) precipitated in the sandstones most likely between 70 and 90 °C; (3) the third zone C (homogeneous CL pattern and directly measured δ¹⁸O values between +16‰ and +22‰) precipitated in the sandstones most likely at temperatures >90 °C. Calculated oxygen isotope compositions of pore waters show that zone A quartz cements, and enclosing concretionary calcite, precipitated from a meteoric-type fluid (∼−7‰) during shallow burial (<1.5 km). Zone B quartz cements precipitated from fluids which evolved in composition from a meteoric-type fluid (δ¹⁸O −7‰) to a more ¹⁸O-enriched fluid (δ¹⁸O −4‰) as burial continued to ∼3.0 km. Data from zone C quartz cements are consistent with further fluid evolution from δ¹⁸O −4‰ to basinal-type fluids with δ¹⁸O similar to the present-day formation water oxygen isotope composition (+0.6‰ at 4.0 km burial). A similar pore water evolution can be derived for all three reservoirs studied, indicating that hydrogeologic evolution was similar across sandstones of the whole Brae Formation.The quartz cement zones observed in the Brae Formation sandstones, and the pore water history derived for the area studied, is analogous to published petrographic and pore water evolution data from the nearby Brent Group reservoirs and from reservoirs located in the Haltenbanken area on the Atlantic margin offshore Norway. Considering quartz cement is a major porosity-occluding phase in many reservoir sandstones, and because pore waters both dissolve quartz and carry the dissolved silica to cementation sites, the data presented are valuable for improving the understanding and prediction of reservoir quality development in sandstones globally.     

钢筋混凝土框架梁的变形能力及基于性能的抗震设计方法

本文以Priestley改进的Mander约束混凝土模型为基础推导了RC梁截面λbv-ξn-μbψ关系的一般计算公式和简化计算公式λbv-ξ-μbψ,建立了配箍特征值λbv、相对受压区高度ξn及曲率延性μbψ三者之间的量化关系式,用于梁截面在目标曲率延性下的变形能力设计,给出了梁截面在目标曲率延性下的设计流程图.对所设计的梁截面进行变形能力验算,均可达到设定的目标曲率延性.在简化的λbv-ξ-μbψ公式基础上建立了框架梁的性能设计方程,即λbv-ξ-θplb关系式,给出了RC框架梁基于性能的抗震设计方法的一般步骤.设计者可灵活地根据性能要求设定可接受的破损指标DI进行梁的性能设计.     

以草酸钠为原料膜法制取草酸和烧碱的研究

本文提供了一个用离子膜电解法生产草酸的新工艺，研究了草酸钠的提纯和制取草酸新方法的工艺条件，求取了技术经济指标，解决了传统工艺的三废污染和产品质低等问题。     

IP-1型离子泵测氦仪及其在放射性水化找矿中的初步试验

讨论了IP—1型离子泵测氦仪的工作原理及基本技术特性。通过野外工作,证明仪器具有性能比较稳定、灵敏度较高,便于携带等特点。介绍了仪器在已知铀矿床上开展放射性水化学找矿的试验结果。测量资料表明,在有利的地质、水文地质条件下,水氦异常能较好的指明深部铀矿化范围。     

Evolution of the REE mineralogy in HP–LT metapelites of the Sebtide complex, Rif, Morocco: Monazite stability and geochronology

REE mineralogy was characterized at the micrometer scale (using scanning electron microscopy) in the four tectono-metamorphic units of the Beni Mzala window, Sebtide Complex, Internal Rif, Morocco, which sample a HP-LT metamorphic gradient from subgreenschist to blueschist/eclogite facies. These tectonic units are composed of garnet-free metapelites (and associated synmetamorphic veins) from the same homogeneous aluminium-rich and calcium-poor protolith. In that context, mineralogical differences between units are assumed to result from contrasted pressure and temperature histories. Light REE-bearing Al-phosphates of the crandallite group with florencite-rich composition and variable goyazite content are the dominant LREE minerals in the lowest-grade units, Tizgarine (300 °C, 3 kbar as peak conditions) and Boquete de Anjera (350 °C, 10 kbar). In the latter unit, metamorphic florencite is associated with MREE-rich monazite. In the schist of the highest-grade units, Beni Mzala 2 (420–450 °C, 12 kbar) and Beni Mzala 1 (550 °C, 16 kbar), associations of allanite-rich epidote and synchisite (a LREE-fluorocarbonate) are found whereas florencite and monazite are no longer observed. At the wall of the quartz–kyanite veins, retrograde monazite-(Ce) with grain size of 20 to 50 μm is the only LREE-bearing mineral. Th–Pb and U–Pb SIMS data on some of these grains yield ages of 21.3 ± 1.7 Ma and 20.9 ± 2.1 Ma, respectively, consistent with previous K–Ar ages obtained on retrograde clay–mica mixtures in rocks from the same locality. The identification of a stability field for monazite in high-pressure aluminous metapelites with an upper thermal-limit below 450 °C as well as the derivation of meaningful U–Pb and Th–Pb SIMS ages demonstrates the monazite potential for dating HP-LT metapelites. However, since, under these conditions, monazite growth occurs below its admitted closure-temperature, these ages must be interpreted on the basis of monazite textural relationships.     

高温燃烧水解-离子选择电极法测定煤中氟

高温燃烧水解-离子选择电极法测定煤中氟,具有灵敏度高、重现性好、干扰少等优点,在测量过程中多注意水解温度、水解时间、氧气通量及试液的pH调节等因素,可以得到更准确、可靠的测量结果。     

连续自动再生化学抑制-离子色谱法测定石膏及其制品中的氟和氯

测定石膏及其制品中的氟化物和氯化物,传统分析方法过程复杂,分析速度慢,准确度及灵敏度低。本文采用超声提取技术提取样品中的氟和氯,以Na2CO3-Na HCO3作为淋洗液,色谱柱分离后通过抑制器降低背景电导,用电导检测器进行检测。通过优化样品前处理和离子色谱分离条件,在测定范围内氟和氯的含量与峰面积呈良好的线性关系(相关系数0.9998),方法检测限为0.15 ng/m L(氟)和0.28 ng/m L(氯),加标回收率为95.0%~99.7%,精密度(RSD)均小于5%(n=8)。本方法采用超声提取技术,无需净化处理即可直接分析,半小时内完成前处理,且避免了目标分析物的损失。与离子选择电极法相比,检测限由μg/m L提升至ng/m L级别。     

特殊荷载作用下钢筋混凝土桥T形梁碳纤维加固的抗弯试验研究

由于特殊荷载过桥而引起桥梁结构损坏的情况时有发生,通过碳纤维布加固T形截面钢筋混凝土梁的试验,分析了T形梁的抗弯承载能力,极限破坏形式以及U形箍的不同粘贴形式对加固的影响。     

土体冻胀与地基梁相互作用的叠加法研究

根据随机介质的思想,土体冻胀引起的地表隆起近似为正态分布。以上海体育场穿越工程为研究背景,由叠加法基本原理,得出多管冻结冻胀叠加法表达式。将非均布的冻胀荷载简化成多段均布荷载,编制matlab程序求解冻土地基上的弹性地基梁方程,得到冻胀与地基梁（结构）相互作用的位移及接触压力,并用实测数据进行了验证。最后对冻胀与基础梁相互作用的影响因素进行计算分析,得出相互作用的冻胀量随地基梁刚度与外荷载增加而减小、随地基弹性接触系数与自由冻胀量增加而增加。