Origin and Distribution Factors of Sour Gases in Natural Gas Reservoirs in the Amu Darya Right Bank Block,Turkmenistan

Through the analysis of original carbon isotopes in the blocks on the right bank of the Amu Darya River, Turkmenistan, it can be firstly concluded that the carbon dioxide (CO₂) in the sour gas reservoirs belongs to the inorganic-origin gas. The origin of hydrogen sulfide (H₂S) in the Amu Darya Right Bank Block is thermochemical sulfate reduction from the detailed analysis of hydrocarbon source rocks data, reservoir characteristics, vitrinite reflectance of organic matter, and sour gas content. Then, the factors affecting the distribution of sour gases in the Amu Darya Right Bank Block were investigated by the analysis of conventional sour gas distribution factors including geological structure, fracture and fault, caprock integrity, sedimentary facies, reservoir types, lithofacies, the source of sulfur and so on. The following basic findings were achieved: ① The basement rift in the study area is conductive to the distribution of CO₂. The caprock integrity contributes to the concentration of CO₂. The gas reservoirs in the biological dike reefs, patch reefs and overthrust zones usually have medium CO₂ content. ② The geological structure and fracture caused the complexity of the distribution of H₂S. The gypsum-salt rock in upper Jurassic-Tithonian is an important sulphur source, and the main hydrocarbon source rocks are also the major sulfur source of H₂S gas reservoirs. Furthermore, the giant gypsum layers in the middle-upper Jurassic Callovian-Oxfordian and the upper Jurassic-Tithonian are conductive to preservation of H₂S, and the small openings and holes in the reservoir is also correlative to the distribution of H₂S. ③ The H₂S in the study area is mostly distributed in the formations with the geothermal temperature of higher than 100 ℃. The open platform deep-water sedimentary facies are harmful to the formation of H₂S. The patch reef and overthrust zones belong to the belts of low H₂S content, however, the biological dike reef zones belong to the belts of medium-high H₂S content. However, the origin and distribution factors of sour gases in natural gas reservoirs were obtained. At the same time, it was pointed out that more necessary and accurately quantitative research is still needed to determine the origin and distribution of acid gases in the Amu Darya Right Bank Block, Turkmenistan.     

泥河水库春季水-气界面二氧化碳通量与其影响因子的相关性分析

利用静态箱-气相色谱法对泥河水库春季水-气界面二氧化碳通量值进行连续24h观测,对其变化趋势及影响因素加以分析。结果表明:泥河水库24h均为大气CO2的源,其碳通量均值为26.50mg/(m2·h),全天源的极大值出现在1∶00为32.38mg/(m2·h),源的极小值出现在13∶00为20.15mg/(m2·h)。在春季影响泥河水库水-气界面CO2通量变化的主要因素是气温、叶绿素和风速,相关系数分别为0.671、0.625、0.253。结论:水库水-气界面CO2通量的变化是多种因素共同作用的结果,春季水库是大气CO2主要碳源之一。     

A comparison of annual and seasonal carbon dioxide effluxes between sub-Arctic Sweden and High-Arctic Svalbard

Recent climate change predictions suggest altered patterns of winter precipitation across the Arctic. It has been suggested that the presence, timing and quantity of snow all affect microbial activity, thus influencing CO₂ production in soil. In this study annual and seasonal emissions of CO₂ were estimated in High-Arctic Adventdalen, Svalbard, and sub-Arctic Latnjajaure, Sweden, using a new trace gas-based method to track real-time diffusion rates through the snow. Summer measurements from snow-free soils were made using a chamber-based method. Measurements were obtained from different snow regimes in order to evaluate the effect of snow depth on winter CO₂ effluxes. Total annual emissions of CO₂ from the sub-Arctic site (0.662–1.487 kg CO₂ m^–2 yr^–1) were found to be more than double the emissions from the High-Arctic site (0.369–0.591 kg CO₂ m^–2 yr^–1). There were no significant differences in winter effluxes between snow regimes or vegetation types, indicating that spatial variability in winter soil CO₂ effluxes are not directly linked to snow cover thickness or soil temperatures. Total winter emissions (0.004–0.248 kg CO₂ m^–2) were found to be in the lower range of those previously described in the literature. Winter emissions varied in their contribution to total annual production between 1 and 18%. Artificial snow drifts shortened the snow-free period by 2 weeks and decreased the annual CO₂ emission by up to 20%. This study suggests that future shifts in vegetation zones may increase soil respiration from Arctic tundra regions.     

流体水化学观测方法在断层土壤气观测中的应用

利用现有水化学观测仪器设备对某些灵敏气体进行观测,比如使用水氡、水质、气体观测仪器设备进行断层土壤气氡、二氧化碳、气体观测的实验研究,并且给出了集气、采气装置的构成方式.氡气和气体观测采用真空负压采样法,使用水氡观测仪器和气相色谱仪.而土壤二氧化碳观测方法可采用碱溶液吸收法,采样时采用真空负压采样法或常压自然吸收法两种方式,还提出了氡气观测中设计采样装置时应注意的事项.     

Negative-emissions technology portfolios to meet the 1.5 °C target

Our carbon-intensive economy has led to an average temperature rise of 1 °C since pre-industrial times. As a consequence, the world has seen increasing droughts, significant shrinking of the polar ice caps, and steady sea-level rise. To stall these issues’ worsening further, we must limit global warming to 1.5 °C. In addition to the economy’s decarbonization, this endeavour requires the use of negative-emissions technologies (NETs) that remove the main greenhouse gas, carbon dioxide, from the atmosphere. While techno-economic feasibility alone has driven the definition of negative-emissions solutions, NETs’ diverse, far-reaching implications demand a more holistic assessment. Here, we present a comprehensive framework, integrating NETs’ critical performance aspects of feasibility, effectiveness, and side impacts, to define the optimal technology mix within realistic outlooks. The resulting technology portfolios provide a useful new benchmark to compare carbon avoidance and removal measures and deliberately choose the best path to solve the climate emergency.     

国外CO2地质储存现状与展望

温室气体CO2的大量排放给全球气候和环境带来的巨大影响,受到了世界各国的关注。实现CO2的深度减排是人类可持续发展的必由之路。CO2地质储存是缓解碳排放行之有效的方法之一。本文通过以下几方面论述了国外CO2地质储存的现状以及对未来的展望：1）CO2捕集机理,2）CO2地质储存,3）CO2地质储存项目现状与未来预测,4）CO2地质储存场地储量评估,5）CO2地质储存监测技术,6）CO2地质储存模拟工具,7）CO2地质存储经费等。     

Comparison of two different equations of state for application of carbon dioxide sequestration

We suggest that different equations of state (EOS) algorithms can and frequently will provide very different predictions of CO₂ migration following injection for sequestration. Rather than carry out an exhaustive examination of all EOS algorithms available, we elected to evaluate this general hypothesis by making detailed comparisons of simulation results of two very common EOS algorithms. We simulated and compared CO₂ migration patterns using two fundamentally different EOS algorithms – Modified Redlich-Kwong EOS (MRKEOS) and Span and Wagner EOS (SWEOS). In general, the predictions of thermophysical properties for both algorithms are close, except for a contrast in the predicted fugacity coefficient of CO₂, which subsequently propagates to a contrast in predicted solubility in water/brine. Typically, MRKEOS underestimates solubility of CO₂ compared to both SWEOS and experimental solubility data. In simulations of CO₂ migration, dissolution rates of separate-phase CO₂ predicted from the two EOS algorithms were significantly different, even for small contrasts in predicted fluid properties from EOS algorithms, resulting in markedly different migration patterns.     

Volatile emissions and gas geochemistry of Hot Spring Basin,Yellowstone National Park,USA

We characterize and quantify volatile emissions at Hot Spring Basin (HSB), a large acid-sulfate region that lies just outside the northeastern edge of the 640 ka Yellowstone Caldera. Relative to other thermal areas in Yellowstone, HSB gases are rich in He and H₂, and mildly enriched in CH₄ and H₂S. Gas compositions are consistent with boiling directly off a deep geothermal liquid at depth as it migrates toward the surface. This fluid, and the gases evolved from it, carries geochemical signatures of magmatic volatiles and water–rock reactions with multiple crustal sources, including limestones or quartz-rich sediments with low K/U (or ^40?Ar/^4?He). Variations in gas chemistry across the region reflect reservoir heterogeneity and variable degrees of boiling. Gas-geothermometer temperatures approach 300 °C and suggest that the reservoir feeding HSB is one of the hottest at Yellowstone. Diffuse CO₂ flux in the western basin of HSB, as measured by accumulation-chamber methods, is similar in magnitude to other acid-sulfate areas of Yellowstone and is well correlated to shallow soil temperatures. The extrapolation of diffuse CO₂ fluxes across all the thermal/altered area suggests that 410 ± 140 t d^− 1 CO₂ are emitted at HSB (vent emissions not included). Diffuse fluxes of H₂S were measured in Yellowstone for the first time and likely exceed 2.4 t d^− 1 at HSB. Comparing estimates of the total estimated diffuse H₂S emission to the amount of sulfur as SO₄²⁻ in streams indicates ~ 50% of the original H₂S in the gas emission is lost into shallow groundwater, precipitated as native sulfur, or vented through fumaroles. We estimate the heat output of HSB as ~ 140–370 MW using CO₂ as a tracer for steam condensate, but not including the contribution from fumaroles and hydrothermal vents. Overall, the diffuse heat and volatile fluxes of HSB are as great as some active volcanoes, but they are a small fraction (1–3% for CO₂, 2–8% for heat) of that estimated for the entire Yellowstone system.     

煤层处置CO2 的二元气- 固耦合数值模拟

利用不可开采煤层处置二氧化碳可以有效控制温室气体的排放量并可驱动和增加煤层气资源的开采量。二氧化碳注入煤层处置后引入一个复杂的CH4-CO2二元气体与煤体的气固耦合问题,耦合了二元气体竞争吸附、竞争扩散,气体渗流以及煤体变形过程。基于COMSOL Multiphysics建立了二元气固耦合的有限元数值模型,并应用数值模拟实验对二元气固耦合进行了机理分析。模拟结果表明,CO2注入煤层后不断驱替CH4,CH4组分明显减少;气体吸附引起的煤层膨胀量可以抵消部分有效应力引起的压缩变形,由于CH4-CO2二元气体较单一CH4引起的煤层吸附膨胀量大,二氧化碳注入煤层后可以缓解煤层的压缩变形;不同孔隙压力条件下,吸附膨胀与孔隙压力两者竞争作用引起的煤层净变形不同,而净变形也控制着煤层孔隙压力和渗流率的变化,煤层渗透整体呈现先降后升,模拟进行到4.66×107 s时煤层渗透率发生反弹。