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1.
水合物开采可能诱发海底滑坡或其他工程地质灾害。实现水合物商业化开采需要中长期稳定产气，长期荷载下储层的蠕变特性是地层稳定性评价的基础力学参数。利用南海水合物储层粉黏土为试验介质在压缩加载条件下的系列固结排水蠕变测量试验结果，对粉黏土的蠕变特性进行了分析。结果表明，加载过程中，含水合物沉积物经历瞬时变形、固结变形和蠕变变形3个阶段；随着加载应力和水合物饱和度的提高，蠕变应变不断增加；修正的Singh-Mitchell蠕变模型可以较好预测不同应力水平和水合物饱和度下粉黏土的蠕变特性。 相似文献
2.
海底温度和海平面变化可以引起海底天然气水合物分解，导致沉积物孔隙内形成超压，改变沉积物有效应力从而触发海底滑坡。本文建立了与此相关的海底滑坡产生的数值模型，并应用于东北太平洋Cascadia陆缘14～9 kaBP期间发生的Orca滑坡形成过程研究。模拟结果显示在最近18 ka海平面逐渐上升的大背景下，18～14 kaBP期间底水温度升高引起其后的天然气水合物稳定带底界快速上移，并在13.7 kaBP达到1.18 m/ka的高底界上移速率，此时Orca地区稳定带底界粗颗粒层内的高饱和度天然气水合物发生分解，产生114 kPa的流体超压，使地层安全系数显著小于1，触发海底滑坡。因此，海底温度升高引起高饱和度天然气水合物分解可能是东北太平洋Cascadia陆缘Orca海底滑坡的主要触发因素。 相似文献
3.
在大陆边缘海底之下几百米深度处普遍观察到BSR,这些沉积物经历近的构造固红或快速堆积,相信BSR与稳定的甲烷水合物（笼形物）的最深部位对应,我们提出了下模式,BSR水合物的形成是在运移着的孔隙流体进水合物稳定域时,由向上运移的孔隙流体排出甲烷,在这个模式里,大多数甲烷产生于水合物稳定带之下,但此深度不足以充分生热,甲烷初始属生物成因,该模式要求从孔隙流体中排出已分解的甲烷,或随孔隙流体向上搬运已散布的游离气,模式解释证据,水合物在稳定域底界处浓聚,大量的甲烷源包含在水合物内,BSRs仅在特殊环境下出现,在深积物正常沉积体制下,不会向上强裂排出流体进入不合物稳定域,,所以BSRs不普遍,由于俯冲带增生楔处构造加厚,荷载增加,引致流体向上排出,该地区快速沉积未固结成岩,这些地区水合物BSRs常见,当孔隙流体进入水合物流体＋水合物与流体域之间的严格边界,然而,需要形成水合物的甲烷数量源自深海钻井有关孔隙流体中烷浓度的有限资料暗示,从上升流体中有效的排出甲烷,可以包含比所需产生游离气的数量少,在大多数流体排出体制,流体向上运移至海底的数量足够连续排出过剩的氯化物及水合物形成时同位素分离的残余物,因此,当观察钻孔资料,没有大量氯化物或同位素异常残留在孔隙流体内,甲烷浓度与稳定域上或下的孔隙流体内CO2量之差别,可以对早期沉积物成岩反应有明显的影响。 相似文献
4.
《海洋地质与第四纪地质》2017,(1)
为深入了解深部上升流体供应甲烷的海底沉积环境中天然气水合物的形成和聚集过程,综合沉积作用、深部上升甲烷流体的对流和扩散作用、甲烷溶解度控制水合物形成等物理过程,建立了天然气水合物形成过程的数学模型,研究水合物在空间和时间尺度上的形成过程。模型通过3个无量纲参数(沉积压实引起的孔隙流体对流与扩散的比率Pe_1、深部流体向上对流传输与扩散的比率Pe_2、深部上升流体的甲烷含量C_(m,ext)~l),形象地描述了天然气水合物在海底沉积中的聚集过程。数值模拟研究表明,天然气水合物首先在稳定带内上部某一位置形成,随后由于沉积作用向下延伸而在稳定带底部形成水合物;水合物演化时间与Pe_1、Pe_2及C_(m,ext)~l呈负相关;水合物含量与Pe1、C_(m,ext)~l负相关,而与Pe_2正相关。甲烷溶解度曲线对水合物形成和分布有重要影响,但深部上升流体的甲烷含量、上升流体的通量决定了整个水合物系统甲烷量的输入和输出,是海底天然气水合物形成的主要控制因素。 相似文献
5.
《海洋地质与第四纪地质》2021,(5)
蠕变是指沉积物在特定应力状态下变形与时间的关系,属于沉积物的固有力学属性。厘清海洋天然气水合物开采过程中储层蠕变的主控因素及其控制机理,对量化评价潜在工程地质风险的发生和演变规律具有重要意义。本文将在综述海洋天然气水合物储层破坏特征的基础上,梳理海洋天然气水合物储层蠕变特征及主控因素,厘清关键科学问题;结合最新研究成果,阐述天然气水合物储层蠕变特征多尺度表征与探测技术体系的基本内涵,简要探讨该领域的未来研究方向。初步分析认为,海洋天然气水合物开采过程中储层蠕变行为是水合物本身及其分解产出过程中的应力、温度、渗流等动态因素综合作用的结果,现有蠕变本构模型无法完全反映上述相变-传热-渗流-应力多场多相多组分耦合过程。为建立适合南海北部水合物储层的蠕变本构,进而为后续开采工程安全设计提供理论支撑,建议从天然气水合物储层的力学性能弱化特征及蠕变各阶段的时效参数两方面入手,从分子尺度、纳微尺度、岩心尺度、中试尺度、矿藏尺度5个层面,建立天然气水合物储层蠕变行为的跨尺度研究方法体系;以南海实际储层样品为研究对象,剖析天然气水合物开采过程中储层蠕变行为的主控因素。 相似文献
6.
沉积物中天然气水合物合成及开采模拟实验研究 总被引：2，自引：0，他引：2
基于自行研发的天然气水合物模拟开采实验装置,进行了电加热法和减压法2种开采技术的实验研究.实验材料采用粒径为0.18～0.25 mm的自然砂,0.03%的十二烷基硫酸钠(SDS)水溶液和高纯甲烷,每次实验都分为水合物合成和开采两个阶段.实验结果表明:水合物首先在沉积物体系上层与外侧生成,然后在体系内部逐渐生成.在电加热法开采过程中,可分为初始分解、沉积物体系升温、大量分解3个阶段,加热点的位置、热量传递方向和速率决定着沉积物中水合物的分解位置和速率,该方法能量利用率较低.在减压法开采过程中,水合物分解速度先快后慢,设置的分解压力越低,分解速度越快. 相似文献
7.
为了全面考虑水合物对沉积物的力学影响,提出了一个改进的水合物沉积物弹塑性损伤本构模型。首先通过分析水合物在沉积物中的存在形式,认为沉积物的力学特性是水合物胶结以及密实两种作用共同影响的结果;然后在弹塑性损伤理论框架内,引入状态相关砂土本构模型来描述水合物填充的影响,从而建立一个能反映体变特性和围压影响的水合物沉积物本构模型;最后,利用已有试验结果对模型进行了验证。此成果可为将来的水合物开采提供参考。 相似文献
8.
《海洋地质与第四纪地质》2017,(5)
含水合物沉积物渗透率是水合物开采相关工作的基础参数之一。稳态法在应用于渗透率较低的多孔介质时存在着稳定渗流难和试验耗时长等缺点。目前,含水合物细颗粒沉积物渗透率试验数据积累明显不足。本文首先介绍了瞬态压力脉冲法的基本原理及数据处理方法,然后以模拟试验验证了瞬态压力脉冲法的适用性,最后探讨了该方法在松散含水合物沉积物渗透率测量方面的应用效果。结果表明:瞬态压力脉冲法近似解处理粉细砂沉积物试验数据效果较好,而处理黏土沉积物试验数据存在明显误差,建议采用数值模拟反演分析的方法处理瞬态压力脉冲法试验数据;瞬态压力脉冲法适用于松散沉积物渗透率测量,在含水合物沉积物渗透率试验研究方面具有潜在的应用前景。 相似文献
9.
海底管道是天然气水合物大规模开采和集输的关键装备。天然气水合物的开采过程会扰动沉积层的结构，改变沉积层的强度和力学特性，诱发海床发生不均匀沉降，并对水合物开采区内海底管道的力学特性产生影响，如引起管道发生大变形、悬跨、屈曲、断裂等。基于ABAQUS有限元软件，建立天然气水合物开采区内“海床-管道”耦合作用模型，模拟了天然气水合物开采过程中海床沉降变形及其对管道应力、应变、弯矩、悬跨等力学行为的影响。研究结果表明，在天然气水合物开采过程中，海床的不均匀沉降将引起管道发生显著位移并发生弯曲，管道的应力、应变随着变形的增大而增大。当海床沉降量达到某一程度时，管道将脱离海床，产生悬跨，并引发涡激振动风险。 相似文献
10.
为弄清天然气水合物油气系统模拟的原理和实现过程及应用,系统分析了水合物油气系统发展历程和技术特色,总结了该技术在墨西哥湾、水合物脊、阿拉斯加北坡及中国天然气水合物研究中的应用。研究认为:天然气水合物油气系统模拟是在研究类似含油气系统中的生烃、排烃、运移、聚集和逸散模拟基础上,对地质模型网格和地质时代进行细化设置,达到对不同地质时期水合物的分布、热成因/生物成因甲烷气的运移、稳定带内水合物形成时期和资源量进行模拟的目的。系统的模拟可以证实含气流体的运移是天然气水合物聚集成藏的重要控制因素,可以预测天然气水合物稳定带的空间分布、地质演化,热成因气和生物成因气生成、运移、聚集并形成天然气水合物的过程,还可以定量计算水合物资源量。目前,中国对于该技术的应用还处于起步阶段,应该深入学习国外成功经验,大力推广,以提高中国天然气水合物理论研究及勘探开发水平。 相似文献
11.
《Marine and Petroleum Geology》2012,35(1):111-118
Potential accumulations of gas hydrates in Alaminos Canyon Block 21 (AC21) in the Gulf of Mexico are thought to occur in a shallow sand-rich interval, stratigraphically separated from sources of free gas below the base of the gas hydrate stability zone (BGHSZ), by an intervening thick layer of clay- and silt-rich sediments. Availability of sufficient gas charge from depth, in addition to local biogenic sourcing is considered key to the formation of gas hydrates in the GHSZ. Implicitly, a detailed understanding of geometries associated with fault and fracture networks in relation to potential gas migration pathways can provide additional confidence that seismic amplitude anomalies are related to gas hydrate accumulations. Delineation of fault and fracture systems from high resolution seismic data in and below the gas hydrates stability zone (GHSZ) was performed using an automated algorithm—Ant Tracking. The capturing of small-scale detail has particular significance at AC21, revealing a pervasive network of typically small-extent discontinuities, indicative of fracturing, throughout this intervening clay- and silt-rich layer of mass-transport deposits (MTDs). Ant Tracking features appear to correlate, to some extent, with potential gas hydrate accumulations, supporting the concept that fracturing possibly provides migration pathways albeit via a tortuous, complex path. This study demonstrates that the Ant Tracking attribute, in conjunction with detailed seismic interpretation and analysis, can provide valuable evidence of potential gas migration pathways. 相似文献
12.
13.
Numerical studies of methane production from Class 1 gas hydrate accumulations enhanced with carbon dioxide injection 总被引：2，自引：0，他引：2
Class 1 gas hydrate accumulations are characterized by a permeable hydrate-bearing interval overlying a permeable interval with mobile gas, sandwiched between two impermeable intervals. Depressurization-induced dissociation is currently the favored technology for producing gas from Class 1 gas hydrate accumulations. The depressurization production technology requires heat transfer from the surrounding environment to sustain dissociation as the temperature drops toward the hydrate equilibrium point and leaves the reservoir void of gas hydrate. Production of gas hydrate accumulations by exchanging carbon dioxide with methane in the clathrate structure has been demonstrated in laboratory experiments and proposed as a field-scale technology. The carbon dioxide exchange technology has the potential for yielding higher production rates and mechanically stabilizing the reservoir by maintaining hydrate saturations. We used numerical simulation to investigate the advantages and disadvantages of using carbon dioxide injection to enhance the production of methane from Class 1 gas hydrate accumulations. Numerical simulations in this study were primarily concerned with the mechanisms and approaches of carbon dioxide injection to investigate whether methane production could be enhanced through this approach. To avoid excessive simulation execution times, a five-spot well pattern with a 500-m well spacing was approximated using a two-dimensional domain having well boundaries on the vertical sides and impermeable boundaries on the horizontal sides. Impermeable over- and under burden were included to account for heat transfer into the production interval. Simulation results indicate that low injection pressures can be used to reduce secondary hydrate formation and that direct contact of injected carbon dioxide with the methane hydrate present in the formation is limited due to bypass through the higher permeability gas zone. 相似文献
14.
Multichannel seismic data, containing high-amplitude reflections from Cenozoic sediments of the Bjørnøya Basin, southwestern Barents Sea, have been studied, inferring the existence of gas hydrate and free gas. The Cenozoic succession comprises Late Palaeocene and Early Eocene claystones and siltstones and locally also some sandstones overlain by Late Pleistocene glaciogenic sediments. The inferred gas hydrate and free gas accumulations are mainly located in the vicinity of larger faults which can be followed up to base Tertiary level, and which seem to have controlled the geographical distribution of the accumulations. Free gas accumulations are inferred to occur most frequently within the Late Palaeocene strata that occur below the gas hydrate stability zone, and indicate that relatively small gas leakages from deeper accumulations have dominated. Larger gas leakages have probably led to gas migration up into the gas hydrate stability zone and, together with the increasing thickness of the hydrate stability zone towards the north, control the distribution of the suspected gas hydrates. The inferred gas leakages are closely related to the Cenozoic evolution of the Barents Sea, and are probably caused by gas expansion due to the removal of up to 1 km of sediments from the Barents Sea shelf and/or reservoir tilting during the Late Cenozoic glaciations which affected this area. 相似文献
15.
新场沙溪庙组气藏是国内典型的低渗致密砂岩气藏,储层具有＂纵向厚度大、平面展布广、盖层遮蔽性能好、盖层与产层应力差值明显＂等适合于大型加砂压裂改造的地质基础和条件。气藏前期采用中小规模压裂时,单井压后表现出了＂产量递减快、稳产效果差＂等不利于气藏提高采气速度和整体采收率的状况。大型压裂是增加人工裂缝半长,延长气井采气寿命,提高开采效益的重要手段。通过对制约和影响大型加砂压裂改造效果的系列关键工艺技术的攻关研究,研发出了低伤害压裂液体系,提出了压裂液强化破胶和高效返排工艺,并对大型压裂施工参数进行优化设计,最终形成了以＂大砂量、大排量、中—高砂浓度、强化破胶＂为特色,以造长缝为核心的大型压裂关键工艺技术方法,并成功完成了最大加砂规模200.5 m^3的超大型水力加砂压裂现场试验。现场应用实践表明,大型压裂具有＂稳产效果好、勘探评价效益优＂的特点。 相似文献
16.
为了探讨琼东南盆地华光凹陷海底天然气水合物稳定带的分布规律，定量研究了静水压力、底水温度、地温梯度和气源组分对水合物稳定带的影响程度。在此基础上，分析了华光凹陷现今甲烷水合物稳定带的厚度分布。最后，综合各因素的历史演化过程，初步探讨了华光凹陷1.05 Ma BP以来天然气水合物稳定带的演化。结果表明:(1)气源组分和海底温度的变化对研究区内水合物稳定带的影响较大；水合物稳定带厚度与海底温度呈良好的线性负相关性。(2)水深超过600 m的海域具备形成天然气水合物的温压条件；超过600 m水深的海域水合物稳定带厚度大部分超过 100 m，其中西北部稳定带的最大厚度超过300 m，是有利的水合物勘探区。(3)华光凹陷1.05 Ma BP以来天然气水合物稳定带厚度经历了快速增厚–窄幅变化–快速减薄和恢复的过程。麻坑群与水合物稳定变化敏感区在空间上具有较好的叠合关系。结合前人的研究成果，推测其形成与天然气水合物的分解释放有关。 相似文献
17.
南海东沙海域天然气水合物与地质构造的关系 总被引：4，自引：0，他引：4
构造作用和构造过程是控制天然气水合物发育和赋存的重要地质因素之一。陆坡区复杂的构造运动能够形成良好的气体运移通道以及欠压实、高孔隙的水合物储集空间。东沙群岛邻近海域具有水深变化大、沉积厚度大、沉积速率高和有机质丰富等天然气水合物有利赋存条件,最新的研究已经在该海域发现了天然气水合物赋存的地球物理证据BSR,针对东沙群岛海域广泛发育的断裂、底辟、海底滑坡等构造,开展了其与天然气水合物成藏的关系研究,可以进一步深入了解天然气水合物在东沙群岛不同地质构造中的分布特征与演化,为该区天然气远景评估提供参考。 相似文献
18.
Emily V.L. Rees Jeffery A. Priest Chris R.I. Clayton 《Marine and Petroleum Geology》2011,28(7):1283-1293
The Indian National Gas Hydrate Program (NGHP) Expedition 1, of 2006, cored through several methane gas hydrate deposits on the continental shelf around the coast of India. The pressure coring techniques utilized during the expedition (HYACINTH and PCS) enabled recovery of gas hydrate bearing, fine-grained, sediment cores to the surface. After initial characterization core sections were rapidly depressurized and submerged in liquid nitrogen, preserving the structure and form of the hydrate within the host sediment. Once on shore, high resolution X-ray CT scanning was employed to obtain detailed three-dimensional images of the internal structure of the gas hydrate. Using a resolution of 80 μm the detailed structure of the hydrate veins present in each core could be observed, and allowed for an in depth analysis of orientation, width and persistence of each vein. Hydrate saturation estimates could also be made and saturations of 20-30% were found to be the average across the core section with some portions showing highs of almost 60% saturation. The majority of hydrate veins in each core section were found to be orientated between 50 and 80° to the horizontal. Analysis of the strikes of the veins suggested a slight preferential orientation in individual sample sections, although correlation between individual sections was not possible due to the initial orientation of the sections being lost during the sampling stage. The preferred vein orientation within sample sections coupled with several geometric features identified in individual veins, suggest that hydraulic fracturing by upward advecting pore fluids is the main formation mechanism for the veined hydrate deposits in the K-G Basin. 相似文献
19.
Muri Basin in the Qilian Mountain is the only permafrost area in China where gas hydrate samples have been obtained through scientific drilling. Fracture-filling hydrate is the main type of gas hydrate found in the Qilian Mountain permafrost. Most of gas hydrate samples had been found in a thin-layer-like, flake and block group in a fracture of Jurassic mudstone and oil shale, although some pore-filling hydrate was found in porous sandstone. The mechanism for gas hydrate formation in the Qilian Mountain permafrost is as follows: gas generation from source rock was controlled by tectonic subsidence and uplift--gas migration and accumulation was controlled by fault and tight formation--gas hydrate formation and accumulation was controlled by permafrost. Some control factors for gas hydrate formation in the Qilian Mountain permafrost were analyzed and validated through numerical analysis and laboratory experiments. CSMGem was used to estimate the gas hydrate stability zone in the Qilian permafrost at a depth of 100–400 m. This method was used to analyze the gas composition of gas hydrate to determine the gas composition before gas hydrate formation. When the overlying formation of gas accumulation zone had a permeability of 0.05 × 10−15 m2 and water saturation of more than 0.8, gas from deep source rocks was sealed up to form the gas accumulation zone. Fracture-filling hydrate was formed in the overlap area of gas hydrate stability zone and gas accumulation zone. The experimental results showed that the lithology of reservoir played a key role in controlling the occurrence and distribution of gas hydrate in the Qilian Mountain permafrost. 相似文献
20.
Evidence of shallow- and deep-water gas hydrate destabilizations in North Atlantic polar continental margin sediments 总被引：1，自引：0，他引：1
Destabilization of gas hydrates from the North Atlantic polar continental margins is geophysically detectable within hydrate
stability zones (HSZ). High-frequency seismic surveys of structures and propagation velocities of compressional waves have
changed the classic conception of a consistently stable hydrate zone. The results are important in two respects: (1) unstable
shallow-water gas hydrates can substantially contribute to the transfer of methane into the atmosphere, and (2) deep-water
gas hydrates also indicate destabilization, which results in slope instability with probably only a secondary role in the
transfer of methane to the atmosphere and thus in the greenhouse effect.
Received: 6 August 1997 / Revision received: 26 January 1998 相似文献