Geomechanical behavior of the reservoir and caprock system at the In Salah CO2 storage project

Almost 4 million metric tons of CO₂ were injected at the In Salah CO₂ storage site between 2004 and 2011. Storage integrity at the site is provided by a 950-m-thick caprock that sits above the injection interval. This caprock consists of a number of low-permeability units that work together to limit vertical fluid migration. These are grouped into main caprock units, providing the primary seal, and lower caprock units, providing an additional buffer and some secondary storage capacity. Monitoring observations at the site indirectly suggest that pressure, and probably CO₂, have migrated upward into the lower portion of the caprock. Although there are no indications that the overall storage integrity has been compromised, these observations raise interesting questions about the geomechanical behavior of the system. Several hypotheses have been put forward to explain the measured pressure, seismic, and surface deformation behavior. These include fault leakage, flow through preexisting fractures, and the possibility that injection pressures induced hydraulic fractures. This work evaluates these hypotheses in light of the available data. We suggest that the simplest and most likely explanation for the observations is that a portion of the lower caprock was hydrofractured, although interaction with preexisting fractures may have played a significant role. There are no indications, however, that the overall storage complex has been compromised, and several independent data sets demonstrate that CO₂ is contained in the confinement zone.In Salah is an industrial-scale carbon capture and storage project located in central Algeria. Between 2004 and 2011, 3.8 million metric tons of CO₂ were injected into an anticlinal structure at ∼1,800 m depth. Storage integrity at the site is provided by a massive, 950-m-thick caprock that sits above the injection interval (Fig. 1). It consists of a number of low-permeability units that work together to limit vertical fluid migration. These are grouped into main caprock units, providing the primary seal, and lower caprock units, providing an additional buffer and some secondary storage capacity.Open in a separate windowFig. 1.Stratigraphic column with interval depths at well KB-502. Depth is given as meters of true vertical depth below the rotary table (m TVD brt) of the drilling rig, a common elevation datum in the oil and gas industry.In June 2011, injection operations halted at the site to allow reevaluation of the injection strategy (1). At the time, several monitoring observations suggested that pressure, and probably CO₂, had migrated vertically into the lower portion of the caprock. Although there are no indications that overall storage integrity has been compromised, these observations raise interesting questions about the geomechanical behavior of the reservoir and lower caprock system.Several hypotheses have been put forward by various groups to explain these observations. These include fault leakage, flow through preexisting fractures, or the possibility that injection pressures hydraulically fractured a portion of the lower seal (2–13). In this work, we evaluate these hypotheses in light of the available data. We suggest that the most likely explanation for the observed behavior is that the lower caprock was hydrofractured, although interaction with preexisting fractures may have played a significant role. Previous studies by Bissell and colleagues (4) and Oye and colleagues (8) have shown that injectivity and microseismic data show indications of fracturing behavior, at least in the reservoir and possibly in the overburden. Here, we use well data to constrain the state of stress in the reservoir and lower caprock, providing strong support for the hydrofracture hypothesis.This work also highlights those monitoring and analysis methods that have been most useful for understanding the field behavior, as well as lessons learned and potential improvements. This perspective can guide future carbon storage projects.     

Systematic determination of absolute absorption cross-section of individual carbon nanotubes

Optical absorption is the most fundamental optical property characterizing light–matter interactions in materials and can be most readily compared with theoretical predictions. However, determination of optical absorption cross-section of individual nanostructures is experimentally challenging due to the small extinction signal using conventional transmission measurements. Recently, dramatic increase of optical contrast from individual carbon nanotubes has been successfully achieved with a polarization-based homodyne microscope, where the scattered light wave from the nanostructure interferes with the optimized reference signal (the reflected/transmitted light). Here we demonstrate high-sensitivity absorption spectroscopy for individual single-walled carbon nanotubes by combining the polarization-based homodyne technique with broadband supercontinuum excitation in transmission configuration. To our knowledge, this is the first time that high-throughput and quantitative determination of nanotube absorption cross-section over broad spectral range at the single-tube level was performed for more than 50 individual chirality-defined single-walled nanotubes. Our data reveal chirality-dependent behaviors of exciton resonances in carbon nanotubes, where the exciton oscillator strength exhibits a universal scaling law with the nanotube diameter and the transition order. The exciton linewidth (characterizing the exciton lifetime) varies strongly in different nanotubes, and on average it increases linearly with the transition energy. In addition, we establish an empirical formula by extrapolating our data to predict the absorption cross-section spectrum for any given nanotube. The quantitative information of absorption cross-section in a broad spectral range and all nanotube species not only provides new insight into the unique photophysics in one-dimensional carbon nanotubes, but also enables absolute determination of optical quantum efficiencies in important photoluminescence and photovoltaic processes.Single-walled carbon nanotubes (SWNTs), a model one-dimensional nanomaterial system, constitute a rich family of structures (1). Each single-walled nanotube structure, uniquely defined by the chiral index (n,m), exhibits distinct electrical and optical properties (2–5). Quantitative information of SWNT absorption cross-section is highly desirable for understanding nanotube electronic structures, for evaluating quantum efficiency of nanotube photoluminescence (5, 6) and photocurrent (7–9), and for investigating the unique many-body effects in 1D systems (10–16). Despite its obvious importance, reliable experimental determination of nanotube absorption cross-section at the single-tube level is still challenging (17). Previous absorption measurements on ensemble nanotube samples only provide averaged behavior (18–20). Recent absorption studies of individual nanotubes, suffering from small absorption signals and/or slow laser-frequency scanning, cannot determine the absolute absorption cross-section and are limited in achievable spectral range (15, 21–23).We demonstrate here a high-sensitivity polarization-based homodyne method to measure nanotube absorption spectra. By manipulating the light polarization, we enhanced the nanotube-induced transmission contrast, ΔI/I, by two orders of magnitude, and this enhanced transmission contrast can be quantitatively related to nanotube absorption cross-section along and perpendicular to the nanotube axis. Using this polarization control together with supercontinuum laser source, we realized high-throughput and broadband absorption measurements at the single-tube level; combined with electron diffraction technique on the same tube, it enables absolute determination of absorption cross-sections of individual chirality-defined nanotubes, to our knowledge for the first time. We obtained quantitative absorption spectra of over 50 SWNTs of different chiralities, and established a phenomenological formula for absorption cross-sections of different nanotubes. The chirality-dependent nanotube absorption spectra reveal unique 1D photophysics in nanotubes, including a universal scaling behavior of exciton oscillator strength and of exciton resonance linewidth.     

神经节苷脂联合纳美芬对一氧化碳中毒迟发性脑病的治疗作用

目的 观察神经节苷脂联合纳美芬对急性一氧化碳中毒迟发性脑病(DEACMP)患者的治疗作用.方法 2012年1月至2016年3月入住河北医科大学附属哈励逊国际和平急救医学部的128例急性一氧化碳中毒迟发性脑病患者,按随机数字表法分为对照组和治疗组,对照组给予神经节苷脂0.lg肌注、高压氧、防治脑水肿及促进脑细胞代谢等治疗,治疗组在常规治疗基础上加用纳美芬0.3 mg静注,两组分别于治疗前及治疗后2周采取静脉血10 mL检测丙二醛(MDA)、超氧化物歧化酶(SOD)、谷胱甘肽过氧化物酶(GSH-PX)活性、一氧化氮(NO)及一氧化氮合酶(NOS)变化,同时观察患者简易精神状态检查量表(MMSE)评分变化,采用t检验比较两组MMSE评分、MDA、NO水平及SOD、GSH-PX、NOS活性的变化,采用X2检验比较治疗2周后两组患者的临床疗效.结果 治疗组总有效率84.4％高于对照组总有效率68.8％,差异有统计学意义(X2=4.354,P=0.037);治疗前两组患者MMSE评分、MDA、NO水平及SOD、GSH-PX、NOS活性比较差异无统计学意义(P＞0.05);治疗后两组患者MDA、NO和NOS水平[对照组:(4.39±1.01) μmol/L、(60.28±9.68) μmol/L、(21.46±5.53) U/mL;治疗组:(3.37±0.83) μmo]/L、(55.29±9.57) μmol/L、(18.71 ±4.40) U/mL]较治疗前[对照组:(5.54±0.96) mol/L、(68.42±12.71)μmol/L、(29.75±6.79) U/mL;治疗组:(5.48 ±1.16) μmol/L、(69.46±16.37) μmol/L、(30.42 ±7.39) U/mL]显著降低(P＜0.05),治疗组低于对照组(P＜0.05);两组患者治疗后MMSE评分及SOD和GSH-PX活性[对照组:(18.30±5.91)、(81.66 ±10.75)U/mL、(60.58 ±9.69) U/L;治疗组:(23.85±7.21)、(96.41±9.64) U/mL、(73.22±9.95)U/L]较治疗前[对照组:(8.93±2.49)、(69.58±8.05) U/mL、(49.35±6.71) U/L;治疗组:(9.14±2.85)、(70.41 ±7.30) U/mL、(48.40±7.89) U/L]均显著提高(P＜0.05),治疗组高于对照组(P＜0.05).结论 神经节苷脂联合纳美芬治疗急性一氧化碳中毒迟发性脑病能有效地降低患者血MDA、NO和NOS的水平、增强SOD和GSH-PX的表达,促进神经功能恢复,临床疗效显著,为指导临床治疗提供重要依据.     

CO2经门脉超声造影在肝癌动物模型中的研究

通过１３只接种Ｗａｌｋｅｒ－２５６瘤株的鼠肝癌模型进行经门静脉的ＣＯ２增强超声造影的研究．超声造影结果显示，肝内呈弥漫性增强，持续较长时间，肝肿瘤显示为低回声区，边界清晰，呈负性增强。说明肝肿瘤缺乏门静脉血供，但ＣＯ２超声增强仍能提高超声对鼠肝肿瘤的显示率。本研究对鼠肝肿瘤的检出率为１００％，显著高于常规超声（１８．２％）。最小的鼠肝肿瘤仅３ｍｍ，超声所测的肿瘤大小与肿瘤标本的大小有显著的相关性。因此，门静脉ＣＯ２超声造影对提高小肝癌的检出有很大的帮助。     

Clinical investigation of a new combined pulse oximetry and carbon dioxide tension sensor in adult anaesthesia

Objective. To test the accuracy of a new combined oxygen saturation and cutaneous carbon dioxide tension (SPO2–PCO2) sensor in a routine adult clinical environment. This probe provides a non-invasive and continuous monitoring of the arterial oxyhaemoglobin saturation, arterial carbon dioxide tension and pulse rate at the ear lobe. The sensor is intended to measure both relevant respiration/ventilation parameters in one single probe. Methods. Ten adult patients were consecutively studied during general anaesthesia. During the first 5 min after sensor placement at the ear lobe, arterial blood samples were drawn each minute. Carbon dioxide tension and oxygen saturation measurements were obtained simultaneously at 1-min intervals. After this period, patients were hyper-, normo- and hypoventilated. After 15 min at each setting, the simultaneously obtained cutaneous and arterial carbon dioxide tension values were compared. Results. A total of 80 comparisons between ear lobe SpO2–PCO2 measurement, finger clip pulse oximetry and arterial blood gas values were analysed. Three minutes after sensor placement, there were no significant differences between ear probe (cutaneous) and arterial carbon dioxide tensions (p = 0.367). Comparison of arterial with cutaneous carbon dioxide values demonstrated an excellent linear correlation (r2 = 0.92), and showed a standard error of estimate (SDEE) of 0.26 kPa (1.95 mmHg) only. The mean difference was –0.08 kPa (–0.60 mmHg) with a limits of agreement range of –0.38 kPa to + 0.22 kPa (–2.85 mmHg to + 1.65 mmHg). Concerning oxygen saturation measurements, the absolute SpO2 value deviated 1% or less from standard pulse oximetry. Conclusions. During general anaesthesia, postoperative recovery and critical care treatment, both monitoring of oxygenation and ventilation is important. Since pulse oximetry estimates only arterial oxygen saturation, periodic blood sampling is still necessary to determine the patients arterial carbon dioxide status. We could demonstrate that the difference between cutaneous and arterial PCO2 was clinically unimportant, and therefore we conclude that the two methods of estimating the patients carbon dioxide status may be used interchangeably. Our results demonstrated that 3 min after sensor placement, the new SpO2–PCO2 sensor prototype proved to be a reliable tool for continuous non-invasive monitoring of oxygenation and ventilation.     

腹腔镜胆囊切除术中二氧化碳气腹对心血管的影响

目的 :观察腹腔镜胆囊切除术 (LC)中二氧化碳气腹对患者心血管的影响。方法 :选择 4 0例ASAⅠⅡ级胆囊结石或胆囊息肉择期行LC的患者 ,术前 30min肌注阿托品 0 .5mg和鲁米那钠 10 0mg ,入室后连接Dash 2 0 0 0监护仪 ,麻醉诱导用药 :咪达唑仑 30 μg/kg ,芬太尼 3μg/kg ,维库溴铵 0 .1mg/kg ,乙咪酯 0 .3mg/kg ,术中以0 .0 8% 0 .1%异丙酚维持 ,并间断吸安氟醚 ,监测并记录入室时、诱导前、插管后、气腹前、气腹后 1,3,5 ,10min的收缩压(SBP)、舒张压 (DBP)、平均动脉压 (MAP)、心率 (HR)、血氧饱和度 (SPO2 )。结果 :病人诱导前的血压、HR、SPO2 与入室时比较无明显变化 (P >0 .0 5 ) ,插管后SBP、MAP显著升高 (P <0 .0 1) ,SBP、DBP、MAP在气腹后 1、3、5、10min都显著的升高 ,与入室时比较差异有非常显著性 (P <0 .0 1) ,但升高的幅度呈下降趋势。HR在整个麻醉过程中无明显变化 (P >0 .0 5 )。SPO2 在插管后显著上升 (P <0 .0 1)。结论 :腹腔镜胆囊切除术中二氧化碳气腹对循环和呼吸虽有一定的影响 ,但在全身麻醉下加强监测和管理 ,这种影响是可以减少或避免的。     

Measurement of carboxyhaemoglobin by spectrophotometry and gas chromatography

Summary. The purpose of this study was to evaluate state-of-the-art spectrophotometry for measurement of carboxyhaemoglobin (COHb). We measured the fractional concentration of COHb in 109 blood samples from patients under investigation of anaemia or with exposure to carbon monoxide (smokers) with the OSM3 Hemoximeter and by gas chromatography. Duplicate measurements were made with both methods in 42 samples. We found only a trivial systematic difference between the two methods. There was, however, a considerable scatter of the measurements, the limits of agreement (95% confidence limits for the difference between the two methods) being —0.98 and 0.86% COHb. The poor agreement between the methods was largely explained by a large random scatter in duplicate spectrophotometric measurements, whereas the method based on gas chromatography was highly reproducible. We conclude that the low accuracy of spectrophotometric measurements of COHb precludes its use for assessment of the endogenous production of CO, but that it may be useful for assessment of exposure to exogenous CO.