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New Approaches for the Production of Hydrocarbons from Hydrate Bearing Sediments  [PDF]
Judith M. Schicks,Erik Spangenberg,Ronny Giese,Bernd Steinhauer,Jens Klump,Manja Luzi
Energies , 2011, DOI: 10.3390/en4010151
Abstract: The presence of natural gas hydrates at all active and passive continental margins has been proven. Their global occurrence as well as the fact that huge amounts of methane and other lighter hydrocarbons are stored in natural gas hydrates has led to the idea of using hydrate bearing sediments as an energy resource. However, natural gas hydrates remain stable as long as they are in mechanical, thermal and chemical equilibrium with their environment. Thus, for the production of gas from hydrate bearing sediments, at least one of these equilibrium states must be disturbed by depressurization, heating or addition of chemicals such as CO 2. Depressurization, thermal or chemical stimulation may be used alone or in combination, but the idea of producing hydrocarbons from hydrate bearing sediments by CO 2 injection suggests the potential of an almost emission free use of this unconventional natural gas resource. However, up to now there are still open questions regarding all three production principles. Within the framework of the German national research project SUGAR the thermal stimulation method by use of in situ combustion was developed and tested on a pilot plant scale and the CH 4-CO 2 swapping process in gas hydrates studied on a molecular level. Microscopy, confocal Raman spectroscopy and X-ray diffraction were used for in situ investigations of the CO 2-hydrocarbon exchange process in gas hydrates and its driving forces. For the thermal stimulation a heat exchange reactor was designed and tested for the exothermal catalytic oxidation of methane. Furthermore, a large scale reservoir simulator was realized to synthesize hydrates in sediments under conditions similar to nature and to test the efficiency of the reactor. Thermocouples placed in the reservoir simulator with a total volume of 425 L collect data regarding the propagation of the heat front. In addition, CH 4 sensors are placed in the water saturated sediment to detect the distribution of CH 4 in the sample. These data are used for numerical simulations for up-scaling from laboratory to field conditions. This study presents the experimental set up of the large scale reservoir simulator and the reactor design. Preliminary results indicate that the catalytic oxidation of CH 4 operated as a temperature controlled, autothermal reaction in a countercurrent heat exchange reactor is a safe and promising tool for the thermal stimulation of hydrates. In addition, preliminary results from the laboratory studies on the CO 2-hydrocarbon swapping process in simple and mixed gas hydrates are presented.
A Counter-Current Heat-Exchange Reactor for the Thermal Stimulation of Hydrate-Bearing Sediments  [PDF]
Judith M. Schicks,Erik Spangenberg,Ronny Giese,Manja Luzi-Helbing,Mike Priegnitz,Bettina Beeskow-Strauch
Energies , 2013, DOI: 10.3390/en6063002
Abstract: Since huge amounts of CH 4 are bound in natural gas hydrates occurring at active and passive continental margins and in permafrost regions, the production of natural gas from hydrate-bearing sediments has become of more and more interest. Three different methods to destabilize hydrates and release the CH 4 gas are discussed in principle: thermal stimulation, depressurization and chemical stimulation. This study focusses on the thermal stimulation using a counter-current heat-exchange reactor for the in situ combustion of CH 4. The principle of in situ combustion as a method for thermal stimulation of hydrate bearing sediments has been introduced and discussed earlier [1,2]. In this study we present the first results of several tests performed in a pilot plant scale using a counter-current heat-exchange reactor. The heat of the flameless, catalytic oxidation of CH 4 was used for the decomposition of hydrates in sand within a LArge Reservoir Simulator (LARS). Different catalysts were tested, varying from diverse elements of the platinum group to a universal metal catalyst. The results show differences regarding the conversion rate of CH 4 to CO 2. The promising results of the latest reactor test, for which LARS was filled with sand and ca. 80% of the pore space was saturated with CH 4 hydrate, are also presented in this study. The data analysis showed that about 15% of the CH 4 gas released from hydrates would have to be used for the successful dissociation of all hydrates in the sediment using thermal stimulation via in situ combustion.
Evaluation of Different CH4-CO2 Replacement Processes in Hydrate-Bearing Sediments by Measuring P-Wave Velocity  [PDF]
Bei Liu,Heng Pan,Xiaohui Wang,Fengguang Li,Changyu Sun,Guangjin Chen
Energies , 2013, DOI: 10.3390/en6126242
Abstract: The replacement of methane with carbon dioxide in natural gas hydrate-bearing sediments is considered a promising technology for simultaneously recovering natural gas and entrapping CO 2. During the CH 4-CO 2 replacement process, the variations of geophysical property of the hydrate reservoir need to be adequately known. Since the acoustic wave velocity is an important geophysical property, in this work, the variations of P-wave velocity of hydrate-bearing sediments were measured during different CH 4-CO 2 replacement processes using pure gaseous CO 2 and CO 2/N 2 gas mixtures. Our experimental results show that P-wave velocity continually decreased during all replacement processes. Compared with injecting pure gaseous CO 2, injection of CO 2/N 2 mixture can promote the replacement process, however, it is found that the sediment experiences a loss of stiffness during the replacement process, especially when using CO 2/N 2 gas mixtures.
Testing a coupled hydro-thermo-chemo-geomechanical model for gas hydrate bearing sediments using triaxial compression lab experiments  [PDF]
Shubhangi Gupta,Christian Deusner,Matthias Haeckel,Rainer Helmig,Barbara Wohlmuth
Physics , 2015,
Abstract: The presence of gas hydrates influences the stress-strain behavior and increases the load-bearing capacity of sub-marine sediments. This stability is reduced or completely lost when gas hydrates become unstable. Since natural gas hydrate reservoirs are considered as potential resources for gas production on industrial scales, there is a strong need for numerical production simulators with geomechanical capabilities. To reliably predict the mechanical behavior of gas hydrate-bearing sediments during gas production, numerical tools must be sufficiently calibrated against data from controlled experiments or field tests, and the models must consider thermo-hydro-chemo-mechanical process coupling in a suitable manner. In this study, we perform a controlled triaxial volumetric strain test on a sediment sample in which methane hydrate is first formed under controlled isotropic effective stress and then dissociated via depressurization under controlled total stress. Sample deformations were kept small, and under these constraints, we assume that concepts of poro-elasticity are essentially valid. We numerically simulate this experiment using a hydro-geomechanical hydrate reservoir code. The results show that the dynamic coupling between transport, reaction, and mechanical processes during methane hydrate formation and dissociation in sandy sediment is captured well, and experimental gas production, dynamic volumetric strain and pressure response were closely reproduced.
A Method to Use Solar Energy for the Production of Gas from Marine Hydrate-Bearing Sediments: A Case Study on the Shenhu Area  [PDF]
Fulong Ning,Nengyou Wu,Guosheng Jiang,Ling Zhang,Jin’an Guan,Yibing Yu,Fenglin Tang
Energies , 2010, DOI: 10.3390/en3121861
Abstract: A method is proposed that uses renewable solar energy to supply energy for the exploitation of marine gas hydrates using thermal stimulation. The system includes solar cells, which are installed on the platform and a distributor with electric heaters. The solar module is connected with electric heaters via an insulated cable, and provides power to the heaters. Simplified equations are given for the calculation of the power of the electric heaters and the solar battery array. Also, a case study for the Shenhu area is provided to illustrate the calculation of the capacity of electric power and the solar cell system under ideal conditions. It is shown that the exploitation of marine gas hydrates by solar energy is technically and economically feasible in typical marine areas and hydrate reservoirs such as the Shenhu area. This method may also be used as a good assistance for depressurization exploitation of marine gas hydrates in the future.
Experimental investigation on permeability of hydrate bearing sediments based on pressure pulse method

- , 2018, DOI: 10.7520/1001-4888-16-273
Abstract: 水合物藏的渗透特性是判断工业开采可行性的重要参数。为了研究以粉细砂为主构成的多孔介质中水合物对其渗透率的影响,基于瞬态压力脉冲法的原理及求解方法,研制了一套适用于测量含水合物沉积物渗透率的实验装置。利用该装置对含不同饱和度二氧化碳水合物的粉细砂样品进行了渗透率测量实验。结果表明,随着粉细砂样品中二氧化碳水合物饱和度的增加,其渗透率呈指数衰减趋势;将实验数据与渗透率模型进行对比,发现实验数据与水合物占据毛细管中心的平行毛细管模型最为相近。据此推断,水合物在细砂样品中的赋存状态以悬浮模式或接触模式为主。
The permeability of hydrate reservoirs is an important parameter to judge the feasibility of industrial exploitation. In order to study the effect of hydrate in porous media composed mainly of silty-fine sands on its permeability, based on principle of pressure pulse method, an experimental device suitable for measuring permeability of hydrate bearing sediment has been developed. Permeability measurement of simulated porous media containing carbon dioxide hydrate with different saturations was carefully carried out by using this device. Results show that the permeability decreases exponentially with the increase of carbon dioxide hydrate saturation in the porous media. Comparing permeability model with the experimental data, it is found that the experimental data are very close to a parallel capillary model, in which, hydrate occupies capillary center. The pore habit of hydrate in sediment is deduced to be floating and contacting
Physical Properties Response of Hydrate Bearing Sediments near Wellbore during Drilling Fluid Invasion

Zheng Mingming
, Jiang Guosheng, Liu Tianle, Peng Li, Ning Fulong, Liu Li, Chen Zhongxuan, Wang Zhen

地球科学(中国地质大学学报) , 2017, DOI: 10.3799/dqkx.2017.035
Abstract: 目前,国内外学者对钻井液侵入水合物地层的室内实验模拟研究停留在较小尺度上且可靠性难以验证,尚需利用与实际地层物性参数较为贴近的沉积物模型,开展大尺度的实验模拟,为改善水合物地层钻井过程中钻井液工艺和测井准确识别与评价水合物储层提供依据.根据墨西哥湾水合物地层主要物性参数指标压制了相应的人造岩心,进行了人造岩心钻井液侵入实验.结果表明:水合物在加热分解过程中,温度与压力呈上升趋势,而电阻率先升高后下降,水合物相平衡条件不仅与温压条件有关,还受孔隙水盐度不断变化的影响。钻井液侵入岩心过程中,压力的传递速率快于热量的传递,易使原始岩心孔隙中的水、气在压力升高而温度尚未改变的情况下生成二次水合物.钻井液温度是水合物分解的主要因素,而压差有利于提高孔隙水压力,保持水合物的稳定.高密度钻井液虽有利于形成高压差和抑制水合物在钻井液中形成,但也会导致钻井液低侵并使井周水合物更易分解.因此,在实际水合物地层钻井中,为了减少钻井安全事故,应在安全密度窗口范围内尽可能提高钻井液密度,选用温度较低的钻井液并加入一定量的动力学抑制剂或防漏失剂.电阻率测井应该选用随钻测井方式或者深侧向测井值,从而避免因水合物分解导致的测井失真.
At present, the laboratory experiment of drilling fluid invasion problem mostly focus on small scale, carrying out largescale experiment based on physical parameters more similar with actual sediment would provide guidance for drilling fluid formulation during actual drilling process in hydratebearing formation and accurate well logging identification and hydrate reservoir evaluation. This experiment were based on artificial cores which were made according to the physical properties of hydratebearing formation in the Gulf of Mexico. Results indicate that the temperature and pressure rise when hydrate is heated to decompose, while the resistivity firstly increases and then decreasse, in which, hydrate equilibrium conditions are not only affected by temperature and pressure, but also by pore-water salinity. During drilling fluid invasion, the pressure spread rate is much faster than heat, hence it is probably that in-situ pore water and gas continue to form hydrate for pressure increase while temperature doesn't change. The high drilling fluid temperature is the main factor controlling hydrate decomposition, and pressure difference between drilling fluid and pore pressure can help improve the pore-water pressure, which is beneficial to hydrate stability. Though high salinity drilling fluids are conducive to higher pressure difference and will inhibit hydrate formation in drilling fluid, it can also lead to gas hydrate dissociation. Therefore, in order to reduce the drilling risks in the hydrate-bearing formation, the density of drilling fluids should be increased during the safe density window range, but the density increase also increases the drilling fluid invasion. Therefore, a certain amount of kinetic inhibitors and fluid loss control agent leak loss control agents should be added in the low temperature drilling fluids. At the same time, the logging while drilling method or deep laterolog data should be chosen so as to avoid the distortion caused by drilling fluid invasion and hydrate decomposition
A Nonlinear Elastic Model for Triaxial Compressive Properties of Artificial Methane-Hydrate-Bearing Sediment Samples  [PDF]
Kuniyuki Miyazaki,Norio Tenma,Kazuo Aoki,Tsutomu Yamaguchi
Energies , 2012, DOI: 10.3390/en5104057
Abstract: A constitutive model for marine sediments containing natural gas hydrate is essential for the simulation of the geomechanical response to gas extraction from a gas-hydrate reservoir. In this study, the triaxial compressive properties of artificial methane-hydrate-bearing sediment samples reported in an earlier work were analyzed to examine the applicability of a nonlinear elastic constitutive model based on the Duncan-Chang model. The presented model considered the dependences of the mechanical properties on methane hydrate saturation and effective confining pressure. Some parameters were decided depending on the type of sand forming a specimen. The behaviors of lateral strain versus axial strain were also formulated as a function of effective confining pressure. The constitutive model presented in this study will provide a basis for an elastic analysis of the geomechanical behaviors of the gas-hydrate reservoir in the future study, although it is currently available to a limited extent.
Experimental Study of Permeability Variation of Hydrate Bearing Sediments with Different Saturations during Effective Stress Loading-Unloading Process

- , 2016, DOI: 10.7520/1001-4888-15-137
Abstract: 为了研究天然气水合物开采过程中水合物饱和度和有效应力变化对含水合物沉积层渗透率变化规律的影响,利用自主研制的水合物沉积物合成与三轴渗流实验一体化装置,进行了有效应力升降过程中不同饱和度水合物沉积物渗透性实验。结果表明:有效应力升降过程中,不同饱和度水合物沉积物的渗透率与有效应力均呈负指数规律变化,并表现出在低有效应力阶段渗透率变化的幅度大于高有效应力阶段;有效应力升降过程中,试样产生的不可恢复变形使渗透率不能完全恢复,造成渗透率永久损失;有效应力不变时,水合物沉积物的渗透率与水合物饱和度呈负指数规律变化,且曲线的斜率随饱和度增加由大变小;水合物的饱和度越大,最大渗透率损害率越大,渗透率恢复的程度越差。
In order to study the influence of hydrate saturation and variation of effective stress during natural gas hydrate mining process on the permeability variation, permeability experiment of hydrate bearing sediment with different saturations during effective stress loading-unloading process was carried out, by using an self-developed integrated device of hydrate sediment synthesis and three-axial seepage experiment. Results show that during effective stress loading-unloading process, the permeability of hydrate bearing sediment with different saturations varies according to negative exponential regulation with the effective stress variation. The permeability variation amplitude at low effective stress stage is greater than that at high effective stress stage. During effective stress loading-unloading process, non-recoverable deformation of specimen causes the permeability can not be completely recovered, resulting in permanent loss of permeability. When the effective stress is constant, the permeability of hydrate bearing sediment varies with saturation according to negative exponential regulation, and the curve slope decreases with the increase of saturation. The greater the saturation degree of hydrate is, the greater the damage rate of maximum permeability, the worse the permeability recovery

WU Shi,|guo,XU Ning,

天然气地球科学 , 2003,
Abstract: Gas hydrate are very important because of their vest resources potential, their role as submarine geohzard, and their effects on global climate in the world. The research result of the gas hydrate in the Mackenzie Delta of Canada are discussed in this summary and conclude the physical and chemical properties of the hydrate\|bearing sediments which are drilled from the permafrost and introduce the evaluation of the gas hydrate.
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