Contact-metamorphic effect on parameters for kerogen maturation

This study examines the effect of contact metamorphism by an igneous dyke on parameters for kerogen maturation, such as elemental composition (H/C, O/C, N/C), ¹H-NMR T₁, vitrinite reflectance and infrared spectra. Although elemental composition and ¹H-NMR T₁ of the kerogen changed only within 1.5 and 5.0 m from the dyke respectively, vitrinite reflectance of the kerogen was thermally affected beyond 10.0 m from the intrusion. It is concluded that vitrinite reflectance is the most sensitive of the parameters evaluated to assess thermal stress of kerogens.     

Pyrolysis of immature Torbanite and of the resistant biopolymer (PRB A) isolated from extant alga Botryococcus braunii. Mechanism of formation and structure of torbanite

Immature Torbanite and the resistant biopolymer (PRB A) isolated from extant B. braunii were previously compared using bulk spectroscopic methods. In the present work, analysis of 400°C pyrolysis products and pyrolysis residues provided further information on their structure and possible relationships. It appears that such polymers are based upon unbranched, saturated, cross-linked hydrocarbon chains up to C₃₁. In addition to these bridging structures, a substantial part of the alkyl chains is singly bound, as esters of unbranched, saturated or cis unsaturated, even fatty acids. These esters are sterically protected, against chemical degradations, by the network of the bioand geopolymer.Quantitative and qualitative observations derived from 400°C pyrolysis confirm that the chemical structure of PRB A and immature Torbanite are closely related. The pyrolysis residues show a similar evolution and numerous common features are noted, with respect to the nature and the distribution of the major constituents of the pyrolysates (hydrocarbons and fatty acids). Accordingly, Botryococcus provides what seems to be the first example of a close structural relationship between a biopolymer produced in large amounts by an extant alga and the geopolymer of an immature kerogen. The essential role of PRB A in Torbanite formation is ascertained. Moreover, it is found that the resistant biopolymer does not undergo important structural changes during the first stages of diagenesis. Thus, owing to steric protection, the esters of immature Torbanite show a distribution quite close to the one of PRB A esters, with exclusively even constituents and a large contribution of unsaturated acids.Recent observations pointed to the possible genesis of some algal kerogens principally by selective preservation of resistant macromolecules. Such a type of formation is clearly predominant in Torbanite, where the bulk of the fossil organic matter corresponds to a selectively preserved and weakly altered, resistant biopolymer, while incorporation of lipids into the kerogen structure during diagenesis seems to play a minor role.     

Elucidation of the Alum Shale kerogen structure using a multi-disciplinary approach

The significance and validity of integrating data obtained from a variety of analytical techniques to understand, elucidate and model kerogen's complex chemical structure is reported here using degradative (open and closed system pyrolysis, chemical oxidation), non-degradative (¹³C CP/MAS NMR) and optical (incident white light and blue light) methods. Seven Cambrian Alum Shale samples, ranging in maturity from immature to post-mature with respect to petroleum generation, were studied and were chosen for their simple geological history, uniform organic matter type and high organic carbon content. The Alum Shale kerogens, which primarily consist of algal organic matter, liberate low molecular weight gaseous and aromatic compounds on pyrolysis and give mostly branched dicarboxylic acids on chemical oxidation. ¹³C NMR spectroscopy shows that the Alum Shale kerogens are anomalously rich in oxygen-bearing functional groups (such as C = O, ArCO, CHO, CH_xO), most of which apparently remain intact within the kerogen macro-molecule (KMM) through the diagenetic and catagenetic stages. Fragments released by different degradative techniques are quantified and the aromaticity (f_a), O/C and relative proportions of various carbon types estimated by ¹³C NMR. A synthesis of these data has allowed us to better understand the chemistry of the Alum Shale kerogen.     

地面核磁共振技术勘查西北干旱浅层地下水效果浅析

地面核磁共振技术勘查地下水是一种新的应用领域,该技术是目前国际上唯一的能直接进行地下水勘查的技术.我所自一九九九年引进法国Numis仪器以来,先后在陕西黄土区、宁南黄土区等地开展寻找不同类型浅层地下水的试验工作,取得了一定的野外成果.本文是在分析总结这些成果的基础上,针对存在的问题如强干扰背景下勘查结果的可靠性,同一测点"8”字型与"正方形”发射线框二者勘查结果比较等方面进行探讨分析.     

复杂地质条件下气层的多参数识别

在复杂地质条件下,应用单一或两种孔隙测井资料直接识别气层,灵敏度不高,为了准确地识别复杂地质条件下的气层,需从不同角度,应用多参数进行综合识别,本文介绍了声波法,中子－密度法,双孔隙度法,中子－伽玛法,等效弹性模量法等,并应用它们对哈盆地两口井进行了重点分析,效果良好。     

基于核磁共振测井资料构建水谱库的流体性质识别方法

以海拉尔地区为例,提出了基于核磁共振T2谱构建水谱库进行流体性质识别的一种新方法,实测核磁谱包含了孔隙结构、水和油气的信息,构建的水谱来自于水层的核磁实测谱,相当于消除了油气的影响,其基本原理是应用构建的水谱库与实测谱的差异识别流体性质。通过在海拉尔地区应用,得到了较好的应用效果。     

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.     

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。     

NMR Measurements in Carbonate Rocks: Problems and an Approach to a Solution

Carbonate rocks are well known for their complex petrophysical behavior where, in contrast to siliciclastic rocks, different parameters, including porosity and permeability, usually are not directly related. This behavior is the result of thorough reorganization of porosity during diagenesis, and it turns prediction of reservoir quality of carbonate rocks into a challenge. The study presented here deals with the problem of utilizing NMR techniques in prediction of petrophysical properties in carbonates.We employ a visual porosity classification as a priori knowledge for better interpreting NMR data for prediction purposes. This allows for choice of suitable T₂ cutoff values to differentiate movable from bound fluids adapted for the specific carbonate rock, thus resulting in better interpretation of NMR data. The approach of using a genetic pore type classification for adapting the conventional method for T₂ cutoff determination, which originally was developed for siliciclastic rocks, is promising. Similarly, for permeability determination on the basis of NMR measurements, the classification of carbonate rocks based on porosity types also shows potential. The approach implemented here has the promise to provide a basis of standardized interpretation of NMR data from carbonate rocks.Acknowledgment We are grateful to Baker Hughes INTEQ, Celle, for permission to publish the results of this work. This study was part of I.S.s Masters Thesis at Hannover University that was carried out in collaboration with Baker Hughes INTEQ, Celle, Germany. We appreciate comments of an anonymous referee and PAGEOPH editor Brian J. Mitchell.     

An infrared and <Superscript>1</Superscript>H MAS NMR investigation of strong hydrogen bonding in ussingite,Na<Subscript>2</Subscript>AlSi<Subscript>3</Subscript>O<Subscript>8</Subscript>(OH)

The mineral ussingite, Na₂AlSi₃O₈(OH), an interrupted tectosilicate, has strong hydrogen bonding between OH and the other nonbridging oxygen atom in the structure. Infrared spectra contain a strongly polarized, very broad OH-stretching band with an ill-defined maximum between 1500 and 1800 cm^–1, and a possible OH librational bending mode at 1295 cm^–1. The IR spectra confirm the orientation of the OH vector within the triclinic unit cell as determined from X-ray refinement (Rossi et al. 1974). There are three distinct bands in the ¹H NMR spectrum of ussingite: a predominant band at 13.5 ppm (TMS) representing 90% of the structural hydrogen, a second band at 15.9 ppm corresponding to 8% of the protons, and a third band at 11.0 ppm accounting for the remaining 2% of structural hydrogen. From the correlation between hydrogen bond length and ¹H NMR chemical shift (Sternberg and Brunner 1994), the predominant hydrogen bond length (H...O) was calculated to be 1.49 Å, in comparison to the hydrogen bond length determined from X-ray refinement (1.54 Å). The population of protons at 15.9 ppm is consistent with 5–8% Al–Si disorder. Although the ussingite crystal structure and composition are similar to those of low albite, the bonding environment of OH in low albite and other feldspars, as characterized through IR and ¹H NMR, is fundamentally different from the strong hydrogen bonding found in ussingite.