液氮冻结条件下岩石孔隙结构损伤试验研究

液氮温度极低,约在-195.56^-180.44℃之间,当与岩石接触时会对岩石孔隙结构产生损伤。根据这一特点,低温液氮有望作为压裂流体对储层进行压裂改造。为了研究液氮冻结对岩石孔隙结构损伤的影响,选取两种不同砂岩岩样,分别在不同初始含水饱和度条件下进行液氮冻结处理。对冻结前、后的岩样进行孔隙度以及核磁共振测试,得到岩样在冻结前、后的孔隙度、横向弛豫时间T2分布以及T2谱面积变化情况。试验结果表明:液氮冻结会对岩石的孔隙结构产生损伤,损伤程度受到岩性、孔隙度和岩石含水饱和度等因素影响;岩石含水饱和度越大,损伤就越严重,当岩石含水饱和度达到100%时,岩石表面产生了明显裂纹;岩石在液氮冻结下损伤形式主要是微孔隙的发育和扩展,微孔隙的增加会使岩石孔隙结构的连通性增强,甚至会产生新的大尺寸孔隙,从而对孔隙结构造成严重损伤。     

低场核磁共振定量测定松散沉积物中含水量的方法

核磁共振通过测定体系中氢质子弛豫的T2谱来确定液态水的含量。采用低场核磁共振技术定量测定松散沉积物体系中的含水量,探讨了沉积物粒径、黏土矿物种类与含量、孔隙水盐度、温度及气体压力等因素对测试结果的影响。由于不同介质体系中孔隙水表面弛豫机制不同,导致低场核磁测定松散沉积物中的含水量偏小。引入校正系数Cm对水量测试值进行了修正,结果表明：沉积物及孔隙水介质本身特性对水量测试结果几乎无影响,相对误差<0.5%,测试精密度<0.20%;温度变化对测试结果影响较大且呈负相关,温度从25 ℃降至1.7 ℃,水量测试值增加了10.71%;压力变化对测试结果的影响与充注气体是否含氢密切相关,不含氢气体的压力变化对测试结果没有影响,而对于含氢气体如甲烷,水量测试结果随压力变化线性增加,甲烷增加到5.05 MPa时,测试结果增加了12.15%。因此,在采用该法测量甲烷水合物生成分解过程中沉积物孔隙水的变化时,必须考虑体系的温度、压力对测试结果的影响,恒温恒压条件下监测的含水量变化能够准确指示甲烷水合物生成分解的微观过程,可望在海洋天然气水合物生成分解微观动力学研究方面得到广泛应用。     

波伏棱（Povlen）型羟基纤蛇纹石的谱学研究

波伏棱型羟基纤蛇纹石是波伏棱型纤蛇纹石矿物的新变种,本文报导它的吸收光谱、红外光谱、穆斯堡尔谱、电子顺磁共振谱和核磁共振谱。 研究表明,吸收光谱是Fe~(3 )和Fe~(2 )的晶场跃迁以及Fe~(2 )→Fe~(3 )的荷移跃迁引起的;红外光谱是OH和Si-O的伸缩振动、OH转动以及Mg-O和Si-O的弯曲振动引起的;穆斯堡尔谱是Fe~(2 )_(八面体)、Fe~(3 )_(八面体)和Fe~(3 )_(四面体)引起的;电子顺磁共振谱是Mn~(2 )_(八面体)、Fe~(3 )_(八面体)和Fe~(3 )_(四面体)引起的;核磁共振谱是管道水,镁八面体和硅氧四面体上的OH引起的;矿物加热到825℃时,结构开始破坏并出现镁橄榄石相。 此外,本文还解释了该蛇纹石颜色的本质,阐明了上述过渡金属离子和OH在该矿物中的结构环境。     

基于SVD和BRD的二维核磁共振测井正则化反演算法研究

二维核磁共振能从"弛豫-扩散"两个维度上展现流体性质,在识别稠油储层方面具有理论优势,是当前核磁共振测井技术的研究热点.本文深入研究二维核磁共振测井原理,系统分析CPMG-DE脉冲序列测量扩散系数与弛豫时间的方法,结合核磁共振二维谱数理模型,提出一种基于SVD和BRD的正则化反演算法.该算法通过SVD压缩数据,采用带非负约束的Tikhonov正则化方法求解流体"弛豫-扩散"分布,并基于BRD算法迭代确定最佳正则化因子.模拟实验与数值分析表明,该算法无需先验信息、运算效率高、相对误差小,在原始数据信噪比低至50时,仍可有效获取流体(T2,D)二维分布.在二维核磁共振测井数据实时解释应用中,该方法较传统反演算法(如TSVD)具有较大优势.同时,在自主研发的核磁共振测井仪测量CuSO4溶液(T2,D)分布的实验显示,本文设计算法对弛豫时间和扩散系数的反演误差分别仅为2%和4%,较TSVD算法有较大改善.     

多尺度孔隙岩石的核磁共振扩散耦合现象及其探测方法

油藏岩石的孔隙连通性是反映流体渗流难易程度的重要参数,对渗透率、有效孔隙度等岩石物理参数的评价具有重要作用.连通的孔隙中,核磁共振（NMR）弛豫的交换会产生扩散耦合现象,可作为孔隙连通性的表征和探测方法.本文提出利用横向弛豫T₂-T₂脉冲序列测量岩石的扩散耦合现象.运用随机游走方法模拟多孔岩石的核磁共振响应特征,分析扩散耦合的影响因素,推导表征扩散耦合强度的弛豫交换速率计算公式.结果表明：孔隙间的扩散耦合强度与T₂-T₂脉冲序列的混合时间呈正相关性,基于双孔弛豫交换模型推导的弛豫交换速率计算公式能够准确表征双尺度孔隙系统的扩散耦合强度.在孔隙尺寸不满足快扩散条件时,会出现与扩散耦合无关的非对角峰信号.针对含多类型孔隙的碳酸盐岩模型,随混合时间的增加,扩散耦合强度变大,一维T₂谱的形态畸变程度加重,在T₂-T₂二维谱中,代表微裂缝、粒间小孔、溶蚀大孔的信号能量变化趋势不同,反映不同类型孔隙间的连通性存在差异.本文的分析与讨论丰富了核磁共振弛豫在岩石物理性质评价中的应用方向,对利用核磁共振评价复杂孔隙岩石的孔隙结构和连通性提供了新思路和新方法.

     

Identification of Fucans from Four Species of Sea Cucumber by High Temperature ~1H NMR

Acidic polysaccharide, which has various biological activities, is one of the most important components of sea cucumber. In the present study, crude polysaccharide was extracted from four species of sea cucumber from three different geographical zones, Pearsonothuria graeffei（Pg） from Indo-Pacific, Holothuria vagabunda（Hv） from Norwegian Coast, Stichopus tremulu（St） from Western Indian Ocean, and Isostichopus badionotu（Ib） from Western Atlantic. The polysaccharide extract was separated and purified with a cellulose DEAE anion-exchange column to obtain corresponding sea cucumber fucans（SC-Fucs）. The chemical property of these SC-Fucs, including molecular weight, monosaccharide composition and sulfate content, was determined. Their structure was compared simply with fourier infrared spectrum analyzer and identified with high temperature 1H nuclear magnetic resonance spectrum analyzer（NMR） and room temperature 13 C NMR. The results indicated that Fuc-Pg obtained from the torrid zone mainly contained 2,4-O-disulfated and non-sulfated fucose residue, whereas Fuc-Ib from the temperate zone contained non-, 2-O- and 2,4-O-disulfated fucose residue; Fuc-St from the frigid zone and Fuc-Hv from the torrid zone contained mainly non-sulfated fucose residue. The proton of SC-Fucs was better resolved via high temperature 1H NMR than via room temperature 1H NMR. The fingerprint of sea cucumber in different sea regions was established based on the index of anomer hydrogen signal in SC-Fucs. Further work will help to understand whether there exists a close relationship between the geographical area of sea cucumber and the sulfation pattern of SC-Fucs.     

Study of macroaggregate composition using FT-IR and H-NMR spectroscopy

Mucous macroaggregates, recently observed in the northern Adriatic in summer of 1997 and late spring of 2000, are primarily the product of phytoplankton (diatom) exudates during favourable environmental conditions in late spring, and can be viewed as macrogels. The FT-IR and ¹H-NMR spectra of macroaggregate samples from the northern Adriatic, collected in different formation stages in July 1997, August 1997, September 1997 and June 2000, as well as of cultured diatom Skeletonema costatum, showed that they are similar and composed of aliphatic components and polysaccharides bonded through carboxylic and amide groups, and organosilicon compounds. The stability of macrogels of macroaggregates is, according to FT-IR and X-ray analyses, most probably enhanced by interactions with entrapped particles of calcite, quartz and clay minerals. These organic-mineral associations seem to be important for mucous phenomena. According to ¹H-NMR spectra, the temporal differences in macroaggregate composition show a relative increasing percentage of organosilicon compounds and aliphatic components bonded to carbohydrates through ester and amide groups, and an increasing ratio between aliphatic structures and carbohydrates. This indicates that aliphatic chains bonded to Si and carbohydrates may contribute to the persistence and stability of macroaggregates in the summer stratified waters in the northern Adriatic, while the temporal decrease of carbohydrate content is most probably due to microbial and photochemical degradation of algal reserve polysaccharides.     

Li_2S─B_2O_3（─LiBr）玻璃的结构表征

用ＮＭＲ和ＸＰＳ技术研究了Ｌｉ２Ｓ─Ｂ２Ｏ３（─ＬｉＢｒ）体系硫氧化物玻璃的结构，结果指出，４─配位硼分数Ｎ４仅仅由玻璃Ｌｉ２Ｓ／Ｂ２Ｏ３摩尔比决定．而与ＬｉＢｒ含量无关，这表明Ｌｉ２Ｓ作为变形剂参与了玻璃网络形成，而ＬｉＢｒ仅作为参杂剂溶解于玻璃基体中，并进入网络间隙。含ＬｉＢｒ玻璃７ＬｉＮＭＲ谱运动变窄说明Ｌｉ＋离子是移迁离子．Ｓ２ｐ的ＸＰＳ解析谱证实了玻璃中桥硫和非桥硫的存在．Ｌｉｌｓ结合能值显示出Ｌｉ＋离了迁移的化学环境。     

Spectroscopic Characterization of Organic Structures and Organic‐Inorganic Interactions in Paper Mill Sludge

The organic composition and organic‐inorganic interaction in paper mill sludge (PS) solvent extracts (hexane, ethyl acetate, acetone and ethanol) and humic fractions, humic acid (HA) and humin (HU) were studied by electron paramagnetic resonance spectroscopy (EPR), proton and carbon‐13 nuclear magnetic resonance spectroscopy (¹H NMR; ¹³C NMR), Fourier‐transformed infrared spectroscopy (FTIR), and ultraviolet‐visible spectroscopy (UV‐vis). The strategy of fractionating the PS, sequentially, with organic solvents of increasing polarity is a reliable analytical procedure for humic substance sample separation because it results in more purified fractions. FTIR, ¹H NMR and ¹³C NMR results showed that hexane extract consisted mainly of aliphatic hydrocarbon structures. Their contents in the extracts decreased as the polarity of the extracting solvent increased and the content of oxygen functional groups increased. Carboxylic and carboxylate functional groups were found in the acetone extract, and ester and ether functions were predominantly found in the ethanol extract. EPR spectra revealed some Fe³⁺ complexes with rhombic structure (g₁ = 4.3; g₂ = 9.0) in the humic fractions and in all solvent extracts, except hexane. Quasi‐octahedral Fe³⁺ complexes (g = 2.3; ΔH_pp ≤ 400 G) were found in the HU fraction and in the acetone extract. The organic free radical content in the HA fraction was higher than the non‐fractionated PS sample and HU fraction.