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.     

Regional drought-induced reduction in the biomass carbon sink of Canada's boreal forests

The boreal forests, identified as a critical "tipping element" of the Earth's climate system, play a critical role in the global carbon budget. Recent findings have suggested that terrestrial carbon sinks in northern high-latitude regions are weakening, but there has been little observational evidence to support the idea of a reduction of carbon sinks in northern terrestrial ecosystems. Here, we estimated changes in the biomass carbon sink of natural stands throughout Canada's boreal forests using data from long-term forest permanent sampling plots. We found that in recent decades, the rate of biomass change decreased significantly in western Canada (Alberta, Saskatchewan, and Manitoba), but there was no significant trend for eastern Canada (Ontario and Quebec). Our results revealed that recent climate change, and especially drought-induced water stress, is the dominant cause of the observed reduction in the biomass carbon sink, suggesting that western Canada's boreal forests may become net carbon sources if the climate change-induced droughts continue to intensify.     

Rapidly growing tropical trees mobilize remarkable amounts of nitrogen, in ways that differ surprisingly among species

Fast-growing forests such as tropical secondary forests can accumulate large amounts of carbon (C), and thereby play an important role in the atmospheric CO₂ balance. Because nitrogen (N) cycling is inextricably linked with C cycling, the question becomes: Where does the N come from to match high rates of C accumulation? In unique experimental 16-y-old plantations established in abandoned pasture in lowland Costa Rica, we used a mass-balance approach to quantify N accumulation in vegetation, identify sources of N, and evaluate differences among tree species in N cycling. The replicated design contained four broad-leaved evergreen tree species growing under similar environmental conditions. Nitrogen uptake was rapid, reaching 409 (±30) kg⋅ha⁻¹⋅y⁻¹, double the rate reported from a Puerto Rican forest and greater than four times that observed at Hubbard Brook Forest (New Hampshire, USA). Nitrogen amassed in vegetation was 874 (±176) kg⋅ha⁻¹, whereas net losses of soil N (0–100 cm) varied from 217 (±146) to 3,354 (±915) kg⋅ha⁻¹ (P = 0.018) over 16 y. Soil C:N, δ¹³C values, and N budgets indicated that soil was the main source of biomass N. In Vochysia guatemalensis, however, N fixation contributed >60 kg⋅ha⁻¹⋅y⁻¹. All species apparently promoted soil N turnover, such that the soil N mean residence time was 32–54 y, an order of magnitude lower than the global mean. High rates of N uptake were associated with substantial N losses in three of the species, in which an average of 1.6 g N was lost for every gram of N accumulated in biomass.     

The urgency of the development of CO2 capture from ambient air

CO(2) capture and storage (CCS) has the potential to develop into an important tool to address climate change. Given society's present reliance on fossil fuels, widespread adoption of CCS appears indispensable for meeting stringent climate targets. We argue that for conventional CCS to become a successful climate mitigation technology-which by necessity has to operate on a large scale-it may need to be complemented with air capture, removing CO(2) directly from the atmosphere. Air capture of CO(2) could act as insurance against CO(2) leaking from storage and furthermore may provide an option for dealing with emissions from mobile dispersed sources such as automobiles and airplanes.     

早期激素干预对急性一氧化碳中毒大鼠迟发性脑病的预防作用

目的观察早期激素干预对急性一氧化碳中毒大鼠迟发性脑病（DEACMP）的预防作用。方法将132只雄性Wistar大鼠随机分成3个实验组：CO中毒组（COP组）、CO中毒＋地塞米松10 mg/kg组（DSMS-10组）和CO中毒＋地塞米松30 mg/kg组（DSMS-30组）,每组40只。另设健康对照组（NC组）,12只。实验组按150 ml/kg腹腔内注射CO制备急性一氧化碳中毒动物模型,健康对照组大鼠注射等体积的空气。在中毒后30 min内DSMS-10组腹腔内注射地塞米松剂量为10 mg/kg/d,共7 d;DSMS-30组腹腔内注射地塞米松剂量为30 mg/kg/d,共7 d;NC组和COP组则注射等剂量生理盐水。监测中毒后90 min、7 d、14 d、21 d各组大鼠血清中髓鞘碱性蛋白（MBP）的含量,并在上述各时间点处死大鼠取脑组织,行HE及MBP免疫组化染色。采用Morris水迷宫实验评估动物的智力状态。结果 Morris水迷宫实验结果显示,COP组中有8只大鼠被判定为迟发性脑病;DSMS-10组中有6只被判定为迟发性脑病;而DSMS-30组和对照组未出现迟发性脑病。COP组大鼠血清中MBP含量增高最显著,DSMS-10组也有增高,DSMS-30组接近正常。差异在中毒后90 min、7 d最明显。病理学检查显示COP组中发生迟发性脑病的大鼠在中毒90 min~21 d后脑海马、皮质下出现神经元损伤、髓鞘碱性蛋白脱失等病理改变,上述病理改变在各实验组中均可观察到,但以COP组大鼠病变程度最重,DSMS-30组最轻。结论10 mg/kg地塞米松可降低急性一氧化碳中毒大鼠迟发性脑病的发生率。30 mg/kg地塞米松则可避免迟发性脑病的发生。     

Efficacy of carbon dioxide-insufflating colonoscopy in patients with irritable bowel syndrome: A randomized double-blind study

Background and Aim: Colonoscopy has the disadvantage of pain and discomfort for patients. It has been shown in randomized controlled trials that carbon dioxide (CO₂) insufflations significantly reduce pain and discomfort in patients undergoing colonoscopy. However, there have been no studies in which CO₂ insufflation in colonoscopy of patients with irritable bowel syndrome (IBS) was investigated. Methods: Randomized double‐blind controlled study was conducted to assess the suffering from colonoscopy in patients with IBS and the efficacy of CO₂ insufflation in colonoscopy for patients with IBS. Patients with IBS and controls who received colonoscopy were randomized into an air or CO₂ insufflation group. Patients' symptoms such as distension and pain were compared using a 10‐cm visual analog scale (VAS). Results: There were 18 patients in the IBS/air group, 19 patients in the IBS/CO₂ group, 25 patients in the control/air group and 26 patients in the control/CO₂ group. The mean value of severity of distension after colonoscopy and the mean value of severity of pain from during examination to one hour after the examination were higher in the IBS group than in the control group. The severity of these symptoms was reduced earlier in the CO₂ group. CO₂ insufflation in colonoscopy was more effective in the IBS group than in the control group from 15 min to one hour after the examination. Conclusion: Regarding colonoscopy‐related suffering, IBS patients showed significant differences from non‐IBS patients. CO₂ insufflation in colonoscopy is effective for IBS patients, particularly for patients who commence activities after colonscopy.     

Ⅳ型胶原酶门脉灌注治疗兔肝硬化有效性与安全性的观察

目的应用四氯化碳(CCl4)诱导兔肝硬化模型,观察Ⅳ型胶原酶门脉灌注对肝硬化程度及全身重要器官组织病理学的影响。方法新西兰大白兔皮下注射50%CCl4橄榄油造模后,将已形成肝硬化并门静脉插管成功的30只兔随机分为2组,组1经门静脉给药通路注入0.1%Ⅳ型胶原酶1.5 mL,组2注入等量0.9%氯化钠,5次/周,共4周。4周后,将各组动物处死,留取各器官组织,观察其病理学变化。结果造模成功后可观察到典型肝硬化病理表现,门脉灌注0.1%Ⅳ型胶原酶肝硬化动物肝脏纤维化程度明显降低,门静脉、心脏、肺、肾脏、脑组织等部位组织病理学无异常表现。结论采用门脉灌注0.1%Ⅳ型胶原酶可显著降低肝纤维化程度,在此剂量下,具有一定的全身安全性。     

CrSO2联合Pcv-aCO2对发绀型婴幼儿心脏手术后ICU停留时间的预测意义

 目的 探究脑氧饱和度(cerebral oxygen saturation,CrSO₂)联合中心静脉动脉二氧化碳分压差(central venous arterial carbon dioxide partial pressure difference, Pcv-aCO₂)对发绀型婴幼儿心脏手术后ICU停留时间的预测意义。方法 选取2018年6-12月在解放军总医院第七医学中心心肺转流(cardiopulmonary bypass, CPB)下接受心脏手术的0~1岁发绀型先心病患儿30例,分别于气管插管开放动静脉后(t₁)、升主动脉夹闭后5 min(t₂)、升主动脉开放后5 min(t₃)、 CPB结束(t₄)、CPB结束后3 h(t₅)、CPB结束后8 h(t₆)、CPB结束后24 h(t₇)记录CrSO₂、动脉血二氧化碳分压(PaCO₂)、中心静脉血二氧化碳分压(PcvCO₂),动脉血孔酸(Lac)、动脉血氧饱和度(SaO₂)、动脉血红蛋白(Hb)、平均动脉压(MAP)、温度氧咽温(T)并计算 Pcv-aCO₂;记录术后ICU停留时间。比较S组(ICU停留时间≤9 d)、L组(ICU停留时间＞9 d)的患儿围术期Lac、CrSO₂、Pcv-aCO₂、SaO₂、Hb、MAP、T的差异,分析Lac、CrSO₂、Pcv-aCO₂对发绀型婴幼儿心脏手术后ICU停留时间的预测意义。结果 S组、L组两组患儿Lac在t₁、t₂、t₃、t₄、t₅、t₆、t₇差异均无统计学意义;与S组相比, L组CrSO₂在t₁、t₂、t₃、t₄明显降低[(53.33±4.38)% &(59.33±4.38)%、(56.83±3.51)% &(63.00±3.67)%、(47.48±5.65)% &(52.51±2.54)%、(44.58±2.42)% &(49.44±3.60)%],t₅、t₆、t₇两组患儿CrSO₂差异无统计学意义;与S组相比,L组Pcv-aCO₂在t₁、t₂、t₃、t₄差异无统计学意义(P＞0.05),在t₅、t₆、t₇明显增高[(16.67±5.28)mmHg &(9.63±3.98)mmHg、(21.83±6.15)mmHg &(12.71±3.10)mmHg、(13.00±2.65)mmHg &(7.36±3.03)]。 S组和L组各时间点PaCO₂、SaO₂、Hb、MAP、T比较,差异均无统计学意义。结论 CPB期间CrSO₂ 降低、CPB结束后 Pcv-aCO₂ 升高对ICU停留时间延长有预测作用。