世界地质储层二氧化碳理论埋存量评价技术研究

埋存CO2是避免气候变化的有效途径之一,地下埋存可供选择的主要方式包括枯竭油气藏埋存、深部盐水储层埋存、不能开采的煤层埋存以及深海埋存等。介绍了各种CO2埋存方式的埋存机理,分析了不同方式下CO2埋存量的各种计算方法。同时给出了IEA和IPCC评估的世界储层CO2埋存量,评估结果表明,深部盐水层可提供巨大的埋存潜力,在400～10000Gt之间;枯竭油气藏也具有很大的埋存潜力,可以埋存全部需埋存C02的40％。CO2地质储层埋存将对全球CO2减排起到举足轻重的作用。     

世界二氧化碳埋存技术现状与展望

埋存CO2是避免气候变暖的主要方法之一,经过十几年的探索,CO2埋存技术取得了很大进步,欧美等世界典型埋存盆地和公司都取得了不错的CO2埋存成果。当前可行的埋存方式有三种:地下埋存、海洋埋存、森林和陆地生态埋存。地下埋存主要选择枯竭的油气藏、深部的盐水储集层、不能开采的煤层及深海埋存等方式。中国在CO2埋存方面具有广阔的前景。CO2埋存前景十分乐观,这一技术的推广和应用必将对全球CO2减排起到举足轻重的作用。     

二氧化碳在深部盐水层中溶解封存规律的研究进展

将二氧化碳埋存到深部盐水层中是目前缓解温室效应的可行性对策之一,在评价储层理论埋存量时,溶解封存量在总埋存量中占有很大的比例。本文通过对相关文献的调研,计算对比了Duan&Sun模型模拟数据与前人实验数据的误差,根据前人实验与本文模拟数据分析了二氧化碳在盐水层中溶解的动力过程和热力过程,二氧化碳通过扩散作用溶解到盐水中,引起盐水层密度的变化,计算系统瑞利数满足对流运动发生的基本条件后,系统产生对流,这有利于二氧化碳的溶解。分析了温度、压力和矿化度对二氧化碳溶解的影响。在前几百年内溶解缓慢易导致泄漏,低温高压、低矿化度下二氧化碳溶解度较高,小二氧化碳水滴更有利于二氧化碳封存。     

管道输运高压氢气与天然气的泄漏扩散数值模拟

基于有限体积法,建立了管道运输高压氢气及天然气的泄漏扩散模型,考虑到氢气与天然气的管道泄漏事故危险性不同,进行了数值模拟与对比,得出了管道泄漏后氢气与天然气的不同泄漏扩散特性.结果表明:高压氢气的泄漏扩散形成的危险云团较大而且集中;氢气初始的泄漏速度比天然气大得多,与周围环境达到压力平衡所需时间较天然气短;随着扩散时间的增加,氢气危险气体云团扩散最大高度较天然气增加得快;在近地面区氢气泄漏扩散产生的危险后果较天然气小.     

水下输油管道泄漏数值研究

输油管道泄漏后不仅造成巨大的经济损失,还会带来严重的环境污染,对生命造成潜在的威胁.目前关于管道泄漏扩散模型的研究多适用于埋地管道及架空输气管道,对于水下管道泄漏扩散问题的研究还很少.基于有限容积法建立水下输油管道泄漏扩散多相流(VOF)模型,借助CFD软件数值计算了影响原油扩散的因素,通过对比发现:当泄漏速度相同,水...     

超临界CO_2的携热优势及在地热开发中的应用潜力分析

利用超临界CO2作为工作介质,循环携带地热或驱替地下热水,是一种新颖的地热开发技术。文章在介绍超临界CO2携热优势的基础上,评价了不同类型地热储层注CO2开采地热的应用潜力。超临界CO2采热能力强,对岩石矿物溶解度小,还可与地质埋存技术相结合,适用于干热岩以及沉积岩地热资源的开发。干热岩开发主要考虑采用超临界CO2作为携热介质,沉积岩地热资源储量丰富、孔隙表面积大、地质条件安全,应是注CO2开采地热和地质埋存的首选。     

世界气候变暖形势严峻 二氧化碳减排工作势在必行

温室气体大量排放而引起的全球气候变暖问题日趋严峻,由此导致的空气污染和温室效应正在严重地威胁着人类赖以生存的环境。为减缓气候变化,就要减少温室气体排放和增加温室气体的吸收,各个国家相继采取积极有效措施。地质埋存CO2是避免气候变化的有效途径,结合气候变暖存在问题,中国政府批准国家973项目——开展温室气体提高石油采收率的资源化利用及地下埋存研究,提出二氧化碳减排发展对策,必将为全球资源和环境的高水平、高效益开发和可持续发展提供理论及实践依据。     

天然气管道环境风险影响分析

对某市天然气输气管道工程不同气象、不同源高条件下事故环境风险的影响范围进行预测与分析.采用气体扩散多烟团模式预测天然气管道泄露及火灾事故的影响范围.结果表明：如果发生天然气泄漏、火灾事故,天然气管道泄漏处下风向的污染物危害范围呈圆环分布;各污染物的扩散多以小风1.5 m/s,稳定度为F类条件下的影响范围最大;在一定的风速和稳定度下,事故影响范围随源高的增高而降低.     

碳酸氢钠分解的热重分析研究

进行了不同压力、气氛及升温速率下的热重试验,研究干法Na2CO3/NaHCO3循环脱除CO2技术吸收剂的预处理和再生过程中NaHCO3的分解特性.通过NaHCO3热解失重率(TG)和失重速率(DTG)曲线,获得相关热解特性参数,研究了CO2:含量、升温速率和压力对NaHCO3分解的影响.结果表明:改变反应气氛的试验以Na2CO3晶体的形成与长大为控制步骤,遵循随机成核随后生长机理;改变升温速率的试验以化学反应为控制步骤,遵循一级反应模型;加压试验以扩散过程为控制步骤,遵循三维扩散机理.给出了相应的反应机理函数.     

罗家寨气田CO2地质封存数值模拟研究

基于罗家寨嘉陵江组建立三维地质模型,利用FLAC3D-TOUGHREACT模拟评估了CO₂注入地层后的地质压力、储层物性变化和CO₂运移规律等。结果表明,在CO₂注入的10年间,CO₂的注入提高了整个地层压力,高压场以注入井为中心呈现梯度递减向四周扩大。储层的孔渗性随着CO₂的注入逐渐增大,而盖层物性未发生明显变化。CO₂羽流主要在中间储层中运移,未突破上下盖层。此外,通过模拟研究发现嘉陵江组的CO₂总封存量为3.211×10⁷ kg。结果说明嘉陵江组所选层位可有效封存CO₂。     

First assessment of an area potentially suitable for underground hydrogen storage in Italy

Hydrogen storage can help achieve climate change and reduce greenhouse gas emissions. This paper presents a first assessment of the suitability of northeastern Italy for underground hydrogen storage (UHS). The study focuses on the analysis of publicly available well data, which allowed identifying geological formations potentially suitable for UHS. The most promising area, known as the “Treviso Area” consists of both saline aquifers and depleted gas fields. One of the key petrophysical properties, i.e. porosity, was calculated for each of the five wells revealing conditions potentially suitable for UHS by applying empirical formulas to geophysical log data. For the two depleted gas fields, a hydrogen injection simulation was also performed. This work is a pioneer study and lays the foundation for hopeful further analyses, which could help implement the recently launched “North Adriatic Hydrogen Valley” initiative.     

Physical, chemical and energy aspects of underground hydrogen storage

Large scale energy storage is becoming an important consideration as we turn more towards nuclear power and the utilization of renewable sources such as solar energy. Underground storage of hydrogen in aquifers has been suggested as an inexpensive method of providing the required energy storage. With this theme in mind, the losses associated with gas storage in aquifers are discussed. These losses include physical leakage of gas, loss of gas through underground chemical reactions and the energy requirements associated with storing and recovering the gas.

Although underground storage of hydrogen appears a most promising solution to the problem of large scale energy storage it is shown that much work remains to be done to confirm this. For example, better estimates of hydrogen diffusion through water saturated porous media are required.     

Hydrogen-induced calcite dissolution in Amaltheenton Formation claystones: Implications for underground hydrogen storage caprock integrity

With the rising potential of underground hydrogen storage (UHS) in depleted oil and gas reservoirs or deep saline aquifers, questions remain regarding changes to geological units due to interaction with injected hydrogen. Of particular importance is the integrity of potential caprocks/seals with respect to UHS. The results of this study show significant dissolution of calcite fossil fragments in claystone caprock proxies that were treated with a combination of hydrogen and 10 wt% NaCl brine. This is the first time it has been experimentally observed in claystones. The purpose of this short communication is to document the initial results that indicate the potential alteration of caprocks with injected hydrogen, and to further highlight the need for hydrogen-specific studies of caprocks in areas proposed for UHS.     

The geo-database of caprock quality and deep saline aquifers distribution for geological storage of CO2 in Italy

One of the most promising options to stabilize and reduce the atmospheric concentration of greenhouse gases is Carbon Capture and Storage (CCS). This technique consists of separating CO₂ from other industrial flue gases and storing it in geological reservoirs, such as deep saline aquifers, depleted oil and/or gas fields, and unminable coal beds.A detailed reworking of all available Italian deep-drilling data was performed to identify potential storage reservoirs in deep saline aquifers. Data were organized into a GIS geo-database containing stratigraphic and fluid chemistry information as well as physiochemical characteristics of the geological formations. Caprock efficiency was evaluated via numerical parameterization of rock permeabilities, defining the “Caprock Quality Factor” (Fbp) for each well. The geo-database also includes strategic information such as the distribution of deep aquifers, seismogenic sources and areas, seismic events, Diffuse Degassing Structures, heat flow, thermal anomalies, and anthropogenic CO₂ sources.Results allow the definition of potentially suitable areas for future studies on CO₂ geological storage located in the fore-deep domains of the Alps and Apennines chains, where efficient marly-to-clayish caprocks lie above deep aquifers hosted in sands or limestones. Most of them are far form seismogenic sources and Diffuse Degassing Structures.     

Influence of capillary threshold pressure and injection well location on the dynamic CO2 and H2 storage capacity for the deep geological structure

The subject of this study is the analysis of influence of capillary threshold pressure and injection well location on the dynamic CO₂ and H₂ storage capacity for the Lower Jurassic reservoir of the Sierpc structure from central Poland. The results of injection modeling allowed us to compare the amount of CO₂ and H₂ that the considered structure can store safely over a given time interval. The modeling was performed using a single well for 30 different locations, considering that the minimum capillary pressure of the cap rock and the fracturing pressure should not be exceeded for each gas separately.Other values of capillary threshold pressure for CO₂ and H₂ significantly affect the amount of a given gas that can be injected into the reservoir. The structure under consideration can store approximately 1 Mt CO₂ in 31 years, while in the case of H₂ it is slightly above 4000 tons. The determined CO₂ storage capacity is limited; the structure seems to be more prospective for underground H₂ storage. The CO₂ and H₂ dynamic storage capacity maps are an important element of the analysis of the use of gas storage structures. A much higher fingering effect was observed for H₂ than for CO₂, which may affect the withdrawal of hydrogen. It is recommended to determine the optimum storage depth, particularly for hydrogen. The presented results, important for the assessment of the capacity of geological structures, also relate to the safety of use of CO₂ and H₂ underground storage space.     

Numerical simulation of leakage and diffusion distribution of natural gas and hydrogen mixtures in a closed container

The transportation and utilization of hydrogen blended natural gas have received extensive attention. The dangerous characteristics of hydrogen such as high diffusivity and wide flammability/explosion limit also increase the leakage risk of hydrogen blended natural gas. In this paper, a numerical model is established for the leakage and diffusion of hydrogen blended natural gas in a closed container. The evolution of the distribution, diffusion law and flammable area of different proportions of hydrogen blended natural gas after leaking into a closed container is investigated. The results show that the flammable area with low hydrogen ratios (20% and below) will disappear within 2.7 s–11.1 s after the leakage, which is relatively safer, while the high hydrogen ratio (80% and above) reaches 3875 s–4555 s with a significant increase in risk duration. After the 50% hydrogen ratio leakage, the thickness of the flammable area is higher than 15.67% for the 80% hydrogen ratio and 30.25% higher than pure hydrogen at 120 s after leakage, and the risk is higher in a short time. Due to the difference in the diffusion rates between methane and hydrogen, hydrogen diffuses to the middle and lower part of the enclosed container faster, and the risk in the middle and lower part also deserves attention.     

Blasingame decline theory for hydrogen storage capacity estimation in shale gas reservoirs

The estimation of storage capacity is crucial for underground hydrogen storage. Shale gas reservoirs have low permeability and porosity, so it is the potential site for hydrogen storage. The study is based on the depleted shale gas reservoirs with multiple flow mechanisms (diffusion, desorption and seepage). Firstly, this paper, using Laplace transformation, point source function and Stehfest inversion, presents a semi-analytical solution for bottom-hole pressure response with hydrogen duration injection. Then we, considering the multiple flow mechanisms, deduce a material balance equation specifically for shale gas reservoirs and plot modified type curves based on the Blasingame decline analysis theory. Furthermore, we discuss the effects of different critical parameters related to hydrogen storage capacity on type curves. In the final part, we describe in detail the method of obtaining hydrogen reserves using type curves. The proposed one can estimate the hydrogen volume in fractures and matrix systems, and get the actual underground storage volume through pressure response, compared with the hydrogen storage capacity calculated by the volumetric method. This study is helpful for the hydrogen capacity estimation of shale gas underground storage on-site.     

A numerical study of hydrogen leakage and diffusion in a hydrogen refueling station

Studies focused on the behavior of the hydrogen leakage and diffusion are of great importance for facilitating the large scale application of the hydrogen energy. In this paper, the hydrogen leakage and diffusion in six scenarios which including comparison of different leakage position and different wind effect are analyzed numerically. The studied geometry is derived from the hydrogen refueling station in China. Due to the high pressure in hydrogen storage take, the hydrogen leakage is momentum dominated. The hydrogen volume concentration with the variation of the leakage time in different scenarios is plotted. More importantly, profiles of the flammable gas cloud at the end of the leakage are quantitatively studied. Results indicate that a more narrow space between the leakage hole and the obstacle and a smaller contact area with the obstacle make the profile of the flammable gas cloud more irregular and unpredictable. In addition, results highlight the wind effect on the hydrogen leakage and diffusion. Comparing with scenario which the wind direction consistent with the leakage direction, the opposite wind direction may result in a larger profile of the flammable gas cloud. With wind velocity increasing, the profile of the flammable gas cloud is confined in a smaller range. However, the presence of the wind facilitates the form of the recirculation zone near the obstacle. With an increase of the wind velocity, the recirculation zone moves downward along the obstacle. Thus, the hydrogen accumulation is more prominent near the obstacle.     

Importance of clay-H2 interactions for large-scale underground hydrogen storage

Underground hydrogen storage is considered an option for large-scale green hydrogen storage. Among different geological storage types, depleted oil/gas fields and saline aquifers stand out. In these cases, hydrogen will be prevented from leaking back to the surface by a tight caprock seal. It is therefore essential to understand hydrogen interactions with shale-type caprocks. To this end, natural pure montmorillonite clay was exposed to hydrogen gas at different pressures (0–50 bar) and temperatures (77, 195, 303 K) to acquire data on its adsorption capacity related to UHS and caprock saturation. Montmorillonite was chosen because of its large specific surface area enabling quantification of the adsorption process. Hydrogen adsorption was successfully fitted with a Langmuir isotherm model and yielded small partition coefficients indicating that hydrogen does not preferentially adsorb to the clay surface. Adsorption on montmorillonite goes back to weak physisorption as inferred from minor negative changes in the enthalpy of reaction (−790 J/mol), derived from an Excel Solver approach to the van't Hoff equation. Based on own as well as literature values, adsorption capacities, which were originally reported as mol/kg or wt%, are recast as hydrogen volume adsorbed per specific surface area (μL/m²). The acquired range is surprisingly narrow, with values ranging from 3 to 6 μL/m², and indicates the normalised volume of hydrogen that can be expected to remain in the shale-type caprock after injected hydrogen migrated upwards through the porous reservoir. This ‘residual’ caprock saturation with hydrogen can be further restrained by considering the geothermal gradient and its effect on the molar volume of hydrogen. The experimental results presented here recommend injecting hydrogen deeper rather than shallower as pressure and temperature work in favour of increased storage volumes and decreased hydrogen loss through clay adsorption in the caprock.