青藏高原天然气水合物的形成与多年冻土的关系

天然气水合物是一种新型清洁能源,赋存在多年冻土区和海洋沉积物等低温高压环境中。青藏高原多年冻土面积占高原总面积的一半以上,是可能的天然气水合物赋存区。根据青藏高原多年冻土条件和天然气水合物形成的热力学条件,讨论了多年冻土地温梯度、冻土厚度与天然气水合物形成的热力学条件之间的关系和青藏高原存在天然气水合物的可能性。结果表明,青藏高原多年冻土区基本具备形成天然气水合物的热力学条件,最适宜的热力学条件是多年冻土地温梯度接近或略大于多年冻土底板附近融土的地温梯度,且融土地温梯度越小,越容易形成天然气水合物。估算得到天然气水合物最浅的顶界埋深为74m左右,最深的底界埋深达上千米。     

青藏高原天然气水合物的形成与多年冻土的关系

天然气水合物是一种新型清洁能源,赋存在多年冻土区和海洋沉积物等低温高压环境中.青藏高原多年冻土面积占高原总面积的一半以上,是可能的天然气水合物赋存区.根据青藏高原多年冻土条件和天然气水合物形成的热力学条件,讨论了多年冻土地温梯度、冻土厚度与天然气水合物形成的热力学条件之间的关系和青藏高原存在天然气水合物的可能性.结果表明,青藏高原多年冻土区基本具备形成天然气水合物的热力学条件,最适宜的热力学条件是多年冻土地温梯度接近或略大于多年冻土底板附近融土的地温梯度,且融土地温梯度越小,越容易形成天然气水合物.估算得到天然气水合物最浅的顶界埋深为74 m左右,最深的底界埋深达上千米.     

青藏高原天然气水合物的形成与多年冻土的关系

天然气水合物是一种新型清洁能源,赋存在多年冻土区和海洋沉积物等低温高压环境中.青藏高原多年冻土面积占高原总面积的一半以上,是可能的天然气水合物赋存区.根据青藏高原多年冻土条件和天然气水合物形成的热力学条件,讨论了多年冻土地温梯度、冻土厚度与天然气水合物形成的热力学条件之间的关系和青藏高原存在天然气水合物的可能性.结果表明,青藏高原多年冻土区基本具备形成天然气水合物的热力学条件,最适宜的热力学条件是多年冻土地温梯度接近或略大于多年冻土底板附近融土的地温梯度,且融土地温梯度越小,越容易形成天然气水合物.估算得到天然气水合物最浅的顶界埋深为74 m左右,最深的底界埋深达上千米.     

南海天然气水合物稳定带厚度及资源量估算

中国的南海一直被人们认为蕴藏着丰富的天然气水合物资源,综合中国南海的水深、地热梯度及底部水温等地质资料,运用VisualBasic.Net编程分析在该海域范围内天然气水合物稳定带厚度,讨论其分布特征,并以此来评估该区域的水合物资源量.结果表明当地热梯度为0.06℃/m,在区域1中可能存在天然气水合物,其稳定带的最大厚度可达400 m,天然气水合物分布较为规则,从外向内逐渐增厚.但在区域2中由于受到水深和地热等因素的影响不存在天然气水合物,此时天然气水合物的资源量约为0.55×104 km3;当地热梯度随机取值时,该区的天然气水合物资源量约为0.57×104 km3.通过对地热梯度取不同的值,估算得到在该研究区天然气水合物的资源量约为0.6×104 km3.      

海底天然气渗漏系统水合物成藏动力学及其资源评价方法

根据海底天然气渗漏系统沉淀水合物的动力学模型,计算了海底渗漏系统中渗漏天然气沉淀为水合物的比例。如果BushHill渗漏系统海底水合物或喷溢天然气的化学组成是渗漏系统气源天然气通过沉淀水合物转变而成,则需要约3. 3% ~21. 7% (平均12. 9% )的渗漏天然气在海底沉淀为水合物。结合渗漏系统的活动时间(1万年)和天然气流量(800t/a),沉淀在墨西哥湾GC185区BushHill渗漏系统中的水合物天然气资源为0. 37×109 ~2. 43×109 m3,平均为1. 45×109 m3,与体积和含量评价方法获得的结果基本一致。     

中国多年冻土区天然气水合物地球化学勘探技术研究进展

我国多年冻土区多位于中纬度高原地区,与环北冰洋极地地区多年冻土的状态不完全相同,天然气水合物成因机理、赋存环境和基本特征更为复杂.近10年来,在自然资源部行业专项和中国地质调查局水合物试采专项的资助下,先后在青藏高原和东北多年冻土区开展了天然气水合物地球化学勘探技术攻关,总结了多年冻土区天然气水合物地球化学指标组合和识别标志,探讨了多年冻土区天然气水合物地球化学成藏机制,研发了多年冻土区天然气水合物地球化学勘查模型,初步建立了多年冻土区天然气水合物调查地球化学方法技术体系,在勘探实践中发挥了重要的作用,地球化学方法技术对天然气水合物的有效性得到了初步检验和应用,具有广阔的应用前景.     

青海木里三露天地区天然气水合物资源量初步评价

在前人工作基础上,重点以青海煤炭地质一0五勘探队在青海木里三露天实施的系列天然气水合物钻井资料为基础,根据已发现天然气水合物产出层位、岩性、深度、气体异常、厚度变化、主控断层等信息,同时通过对地质异常、三维地震、测井化探、微生物多种方法技术的成果对比和分析,在平面上确定出研究区天然气水合物分布区块,进一 步运用体积法估算了青海木里聚乎更煤矿区三露天地区天然气水合物资源量,并对其经济可采性进行了初步评价。结果显示,三露天地区天然气水合物烃类气体控制的地质储量和推测的地质 储量分别为213.85万m³和452.60万m³;结合对三露天调查区天然气水合物的地质认识、资源量、开采技术条件等因素的综合分析,认为调查区天然气水合物赋存情况复杂、资源量偏低、开 采技术不成熟,目前暂不具备经济开采价值。     

AMT正演模拟及反演求导方法在探测冻土厚度中的应用——以青海木里地区多年冻土层为例

作为冻土区天然气水合物重要的成藏因素——盖层冻土的厚度,其勘探方法多样且各具特点。选择性价比较高的音频大地电磁测深(AMT)为探测技术,以青海木里地区为研究对象,通过多种典型模型的AMT正演模拟,并对正演响应进行一维自适应正则化反演与分析,结果表明一维正则化反演曲线取对数求导曲线(或称地层界面分层因子曲线)可较好地划分多年冻土层底板,并在木里地区划分多年冻土厚度中取得了较好的应用效果,为冻土区天然气水合物靶区预测提供良好的支撑作用。由过井DK9的两条十字剖面研究表明,井DK9附近的多年冻土厚度起伏变化不大,约在60~100 m之间变化,为天然气水合物的富集提供了良好的盖层条件。其中,垂直于断裂构造方向DK9-2剖面的多年冻土厚度变化较大,约为60~100 m;平行于断裂构造方向的DK9-1剖面的多年冻土厚度变化较小,为68~92 m。     

天然气水合物的资源环境效应

天然气水合物是一种具有巨大潜能的绿色能源 ,全世界储量接近 0 .84× 10 1 8m3。由于天然气水合物具有特殊亚稳定状态的成矿系统 ,,增温或减压会使捕获的气体释放 ,导致海底滑塌和滑坡等地质灾害 ,以及作为“温室气体”对人类生存环境的严峻挑战 ,因而其又具有环境效应。结合挪威的实例论述了天然气水合物的资源和环境双重效应     

青藏高原具有水合物形成条件

<正> 天然气水合物除了大量赋存于海洋大陆架部位,还可以赋存于高纬度和高原永久冻土带分布区。青藏高原是中国多年冻土集中分布区,冻土带面积达1.588×10~6km~2,占高原总面积的61%,世界多年冻土面积的7%。地质资料分析认为西藏地区有形成天然气水合物的必要条件,在海相盆地     

Growth behavior and resource potential evaluation of gas hydrate in core fractures in Qilian Mountain permafrost area,Qinghai-Tibet Plateau

The Qilian Mountain permafrost area located in the northern of Qinghai-Tibet Plateau is a favorable place for natural gas hydrate formation and enrichment, due to its well-developed fractures and abundant gas sources. Understanding the formation and distribution of multi-component gas hydrates in fractures is crucial in accurately evaluating the hydrate reservoir resources in this area. The hydrate formation experiments were carried out using the core samples drilled from hydrate-bearing sediments in Qilian Mountain permafrost area and the multi-component gas with similar composition to natural gas hydrates in Qilian Mountain permafrost area. The formation and distribution characteristics of multi-component gas hydrates in core samples were observed in situ by X-ray Computed Tomography (X-CT) under high pressure and low temperature conditions. Results show that hydrates are mainly formed and distributed in the fractures with good connectivity. The ratios of volume of hydrates formed in fractures to the volume of fractures are about 96.8% and 60.67% in two different core samples. This indicates that the fracture surface may act as a favorable reaction site for hydrate formation in core samples. Based on the field geological data and the experimental results, it is preliminarily estimated that the inventory of methane stored in the fractured gas hydrate in Qilian Mountain permafrost area is about 8.67×10¹³ m³, with a resource abundance of 8.67×10⁸ m³/km². This study demonstrates the great resource potential of fractured gas hydrate and also provides a new way to further understand the prospect of natural gas hydrate and other oil and gas resources in Qilian Mountain permafrost area.©2023 China Geology Editorial Office.     

Gas Hydrates in the Qilian Mountain Permafrost, Qinghai, Northwest China

Qilian Mountain permafrost, with area about 10×104 km2, locates in the north of Qinghai-Tibet plateau. It equips with perfect conditions and has great prospecting potential for gas hydrate. The Scientific Drilling Project of Gas Hydrate in Qilian Mountain permafrost, which locates in Juhugeng of Muri Coalfield, Tianjun County, Qinghai Province, has been implemented by China Geological Survey in 2008–2009. Four scientific drilling wells have been completed with a total footage of 2059.13 m. Samples of gas hydrate are collected separately from holes DK-1, DK-2 and DK-3. Gas hydrate is hosted under permafrost zone in the 133–396 m interval. The sample is white crystal and easily burning. Anomaly low temperature has been identified by the infrared camera. The gas hydrate-bearing cores strongly bubble in the water. Gas-bubble and water-drop are emitted from the hydrate-bearing cores and then characteristic of honeycombed structure is left. The typical spectrum curve of gas hydrate is detected using Raman spectrometry. Furthermore, the logging profile also indicates high electrical resistivity and sonic velocity. Gas hydrate in Qilian Mountain is characterized by a thinner permafrost zone, shallower buried depth, more complex gas component and coal-bed methane origin etc.     

羌塘盆地QK-1孔烃类气体分布特征与成因来源

青藏高原冻土区面积约150×104 km²,是中国最大的冻土区,具备良好的天然气水合物形成条件和找矿前景,而羌塘盆地是形成条件和找矿前景最好的地区。南羌塘盆地毕洛错地区QK-1科学钻探试验井顶空气样品的烃类气体组分和碳同位素分析测试结果表明,其烃类气体组分复杂,CH₄含量为3.0×10^-6~4 526.8×10^-6,平均为209.0×10^-6;δ¹³C₁值为-55.9‰~-37.8‰,平均为-43.2‰,C₁/(C₂+C₃)值小于10,显示出明显的热解气特征。结合钻探区的地质背景和岩性特征,推断QK-1孔烃类气体可能来源于深部迁移上来的热解气,浅部可能有生物成因气的混入。     

Natural gas hydrates in the Qinghai-Tibet Plateau: Characteristics,formation, and evolution

The Qinghai-Tibet Plateau (also referred to as the Plateau) is the largest area bearing alpine permafrost region in the world and thus is endowed with great formation conditions and prospecting potential of natural gas hydrates (NGH). Up to now, one NGH accumulation, two inferred NGH accumulations, and a series of NGH-related anomalous indicators have been discovered in the Plateau, with NGH resources predicted to be up to 8.88×10¹² m³. The NGH in the Qinghai-Tibet Plateau have complex gas components and are dominated by deep thermogenic gas. They occur in the Permian-Jurassic strata and are subject to thin permafrost and sensitive to environment. Furthermore, they are distinctly different from the NGH in the high-latitude permafrost in the arctic regions and are more different from marine NGH. The formation of the NGH in the Plateau obviously couples with the uplift and permafrost evolution of the Plateau in spatial-temporal terms. The permafrost and NGH in the Qilian Mountains and the main body of the Qinghai-Tibet Plateau possibly formed during 2.0–1.28 Ma BP and about 0.8 Ma BP, respectively. Under the context of global warming, the permafrost in the Qinghai-Tibet Plateau is continually degrading, which will lead to the changes in the stability of NGH. Therefore, The NGH of the Qinghai-Tibet Plateau can not be ignored in the study of the global climate change and ecological environment.©2021 China Geology Editorial Office.     

中国陆域天然气水合物调查研究主要进展

我国是世界上既有海域水合物也有陆域水合物的少数几个国家之一。中国地质调查局高度重视陆域水合物调查研究,2016年正式设立“陆域天然气水合物资源勘查与试采工程”,通过对我国重点冻土区开展地质、地球物理和钻探调查,研发有效的陆域水合物调查、钻探和资源评价技术,初步摸清资源家底,评价资源潜力。自2002年开始探索性调查以来,已在青海省发现木里天然气水合物产地1处、昆仑山垭口盆地和乌丽地区疑似产地2处及系列找矿线索,评价出南祁连盆地、羌塘盆地及漠河盆地三大成矿远景区、12个成矿区带,资源潜力巨大; 在祁连山木里地区成功实施单直井和水平对接井试采,并取得了陆域天然气水合物成矿理论、勘采技术、环境调查和平台建设系列成果。以上成果有力推进了我国天然气水合物资源勘查试采进程,支撑国务院将天然气水合物设为第173个新矿种,初步形成“海陆并举、资环并重”的良好局面。     

干旱区内陆河流域的生态安全与生态需水量研究

结合对干旱区生态安全和生态需水量关键科学问题的探讨,提出干旱内陆河流域生态脆弱区的生态安全分析是以水过程研究为核心的,水文过程控制着生态过程,对流域生态系统的稳定性有着直接影响,而水资源开发利用和水循环对生态系统功能有重要影响,天然植物恢复和生长的合理地下水位的研究是确立生态需水量的基础。并实证分析和计算了维系塔里木河生态安全的生态需水量,塔里木河干流现状生态需水量为31.74×10⁸ m³,其中,上、中、下游分别为9.95×10⁸m³、18.47×10⁸m³和3.32×10⁸m³。     

Analysis of the gas hydrate accumulation condition in Quemocuo area of Qiangtang Basin

Based on the survey results of QK-8 gas hydrate drilling test well and the clue of high hydrocarbon gas in Quemocuo area, the authors systematically analyzed the influence of permafrost thickness on natural gas hydrate accumulation, hydrocarbon source rocks characteristics, reservoir space, mitigation system and other geological factors, considering the geological factors affecting gas hydrate accumulation in permafrost regions. The potential of gas hydrate accumulation was also clarified. The results show that the thickness of permafrost is large (100 m). Hydrocarbon source rocks of Triassic have a overall performance of high abundance of organic matter, with kerogen type Ⅱ₂ and higher maturity (R_o about 1.3%~1.5%). The reservoir space is mainly composed of cavity - fractured reservoirs, followed by fracture and pore types. It has an effective migration pathway and a good regional cap layer. At the same time, natural gas hydrate associated minerals such as calcite and pyrite were well developed in the multilayer sections. It is concluded that there is a certain potential for gas hydrate accumulation in Quemocuo area after comprehensive analysis, which is the main direction for the comprehensive energy resources investigation of the gas hydrate petroleum system.     

羌塘盆地雀莫错地区天然气水合物成藏条件分析

基于天然气水合物钻探试验井QK-8井的调查成果,以雀莫错地区发现的高烃类气体显示为线索,从影响高山冻土区天然气水合物成藏的关键地质因素出发,系统分析了影响天然气水合物成藏的冻土厚度、烃源岩特征、储集空间、疏导系统、矿物特征及盖层条件等地质因素,明确了该区天然气水合物成藏潜力。结果显示: 雀莫错地区冻土厚度较大(约100 m); 上三叠统主力烃源岩整体表现为有机质丰度高,为Ⅱ₂型干酪根,成熟度较高(R_o为1.3%~1.5%); 储集空间以缝洞型储层为主,裂隙、孔隙型次之; 具备有效的运移通道和良好的区域盖层,同时多层段发育方解石和黄铁矿等天然气水合物伴生矿物。综合分析认为,雀莫错地区具有一定的天然气水合物成藏潜力,是下一步天然气水合物含油气系统综合能源资源调查的主要方向。     

青海祁连山冻土区天然气水合物资源量的估算方法——以钻探区为例

祁连山冻土区天然气水合物DK-1、DK-2、DK-3、DK-4号钻孔揭示,该区天然气水合物及其异常主要产出于破碎岩层裂隙中和砂岩孔隙中,根据不同的赋存类型分别赋予具体地质含义,并运用体积法建立了2种产状天然气水合物资源量的计算方法。基于野外地质观测统计数据和室内分析测试结果,在钻探区约40×104m2的范围内,计算得到砂岩孔隙中的天然气水合物资源量约为6.24×104m3天然气,破碎岩层裂隙中的天然气水合物资源量约为88×104m3天然气,总的资源量约为94.2×104m3天然气。可以看出,钻探区中产于破碎岩层裂隙中的天然气水合物资源量是主体,这与钻探中肉眼观察的结果一致。     

Change trend of natural gas hydrates in permafrost on the Qinghai-Tibet Plateau (1960–2050) under the background of global warming and their impacts on carbon emissions

Global warming and the response to it have become a topic of concern in today’s society and are also a research focus in the global scientific community. As the world’s third pole, the global warming amplifier, and the starting region of China’s climate change, the Qinghai-Tibet Plateau is extremely sensitive to climate change. The permafrost on the Qinghai-Tibet Plateau is rich in natural gas hydrates (NGHs) resources. Under the background of global warming, whether the NGHs will be disassociated and enter the atmosphere as the air temperature rises has become a major concern of both the public and the scientific community. Given this, this study reviewed the trend of global warming and accordingly summarized the characteristics of the temperature increase in the Qinghai-Tibet Plateau. Based on this as well as the distribution characteristics of the NGHs in the permafrost on the Qinghai-Tibet Plateau, this study investigated the changes in the response of the NGHs to global warming, aiming to clarify the impacts of global warming on the NGHs in the permafrost of the plateau. A noticeable response to global warming has been observed in the Qinghai-Tibet Plateau. Over the past decades, the increase in the mean annual air temperature of the plateau was increasingly high and more recently. Specifically, the mean annual air temperature of the plateau changed at a rate of approximately 0.308–0.420°C/10a and increased by approximately 1.54–2.10°C in the past decades. Moreover, the annual mean ground temperature of the shallow permafrost on the plateau increased by approximately 1.155–1.575°C and the permafrost area decreased by approximately 0.34×10⁶ km² from about 1.4×10⁶ km² to 1.06×10⁶ km² in the past decades. As indicated by simulated calculation results, the thickness of the NGH-bearing permafrost on the Qinghai-Tibet Plateau has decreased by 29–39 m in the past 50 years, with the equivalent of (1.69 – 2.27)×10¹⁰–(1.12–1.51)×10¹² m³ of methane (CH₄) being released due to NGHs dissociation. It is predicted that the thickness of the NGH-bearing permafrost will decrease by 23 m and 27 m, and dissociated and released NGHs will be the equivalent of (1.34–88.8)×10¹⁰ m³ and (1.57–104)×10¹⁰ m³ of CH₄, respectively by 2030 and 2050. Considering the positive feedback mechanism of NGHs on global warming and the fact that CH₄ has a higher greenhouse effect than carbon dioxide, the NGHs in the permafrost on the Qinghai-Tibet Plateau will emit more CH₄ into the atmosphere, which is an important trend of NGHs under the background of global warming. Therefore, the NGHs are destructive as a time bomb and may lead to a waste of efforts that mankind has made in carbon emission reduction and carbon neutrality. Accordingly, this study suggests that human beings should make more efforts to conduct the exploration and exploitation of the NGHs in the permafrost of the Qinghai-Tibet Plateau, accelerate research on the techniques and equipment for NGHs extraction, storage, and transportation, and exploit the permafrost-associated NGHs while thawing them. The purpose is to reduce carbon emissions into the atmosphere and mitigate the atmospheric greenhouse effect, thus contributing to the global goal of peak carbon dioxide emissions and carbon neutrality.©2022 China Geology Editorial Office.