ARTICLE pubs.acs.org/EF
Experimental Investigation into Methane Hydrate Decomposition during Three-Dimensional Thermal Huff and Puff Xiao-Sen Li,*,†,‡ Yi Wang,†,‡,§ Gang Li,†,‡ Yu Zhang,†,‡ and Zhao-Yang Chen†,‡ †
Key Laboratory of Renewable Energy and Gas Hydrate, Guangzhou Institute of Energy Conversion, and ‡Guangzhou Center for Gas Hydrate Research, Chinese Academy of Sciences, Guangzhou 510640, People’s Republic of China § Graduate University of Chinese Academy of Sciences, Beijing 100083, People’s Republic of China ABSTRACT: In this work, the decomposition behavior of methane hydrate in porous media was investigated in the threedimensional cubic hydrate simulator (CHS) using the huff and puff method with a single well, which is divided into three stories, distributed in the center line position of the reactor. The thermal huff and puff process is analyzed, and it is concluded that each huff and puff cycle includes three stages: heat injection, soaking, and gas production. The injected heat spreads out from the injection point. The region impacted by heat diffusion enlarges as the number of huff and puff cycles increases and eventually reaches the largest impact region. After that, the region impacted by heat diffusion is no longer increasing with continuous heat injection. The change characteristics of the injection temperature, pressure, resistance ratio, and other related parameters during the injection are obtained. The result also verifies that the hydrate decomposition process is a moving boundary ablation process in the threedimensional level.
1. INTRODUCTION Natural gas hydrates are non-stoichiometric crystalline, inclusion compounds, formed from the reaction between natural gas and water under a certain temperature and pressure. Gas hydrate formation requires relatively low temperature and high pressure, and 1 m3 of nature gas hydrate can release 160180 m3 of natural gas under standard conditions. Natural gas hydrates are distributed all over the earth on both the land and offshore and are considered as a potential energy source.13 To exploit this large energy resource, the researchers have proposed many methods, such as (1) the thermal stimulation method,46 in which the hydrate reservoirs are heated above the equilibrium hydrate decomposition temperature using in situ combustion or injecting hot water, steam, or hot salt water to decompose the hydrates, (2) the depressurization method,7 in which the hydrate reservoir pressure is reduced below the equilibrium decomposition pressure to decompose the hydrates, (3) the chemical injection method,8 in which the chemicals (such as methanol or ethylene glycol) are injected to change the equilibrium hydrate decomposition conditions and, thus, to decompose the hydrates. The other two recent ideas that need experimental and field confirmation include CO2 replacement,9 to inject liquid CO2 into offshore hydrate reservoirs by forming CO2 hydrate and replacing the methane gas, and gas lift,10 to lift the hydrate particle as a solid from the sea bottom. Gas production strategies often involve combinations of these dissociation methods.11 In 1982, Holder et al.12 first demonstrated the feasibility of the thermal exploitation technology of the hydrates from a thermodynamic point of view. Roadifer et al.13 raised a two-dimensional finite differential thermal exploitation model under a cylindrical coordinate, and Liu et al.14 gave the schematic diagram of the model and used this model to simulate the decomposition process of gas hydrates in porous media. Selim et al.15 established r 2011 American Chemical Society
the gas hydrate decomposition model under heating, in which they consider the hydrate decomposition as a moving boundary ablation process. Ullerich et al.16 studied the thermal decomposition of methane hydrate based on a planar one-dimensional semi-infinite heat-conduction-controlled experimental system and verified the gas hydrate decomposition model under heating given by Selim et al.15 Until now, the experimental study of methane hydrate exploitation under heating has been limited to one-dimensional4,5 and two-dimensional17 simulations, and the corresponding mathematical model cannot be fully verified. In fact, the actual natural gas hydrate reservoir is a three-dimensional mine. Therefore, to understand more realistic behavior of gas hydrate production, three-dimensional experimental simulation of natural gas hydrate production, especially three-dimensional investigation into the decomposition behavior of gas hydrate, is significant. However, little literature on this aspect has been reported thus far. In this work, the novel developed three-dimensional cubic hydrate simulator (CHS) for the production of gas hydrate is used to investigate the decomposition behaviors of methane hydrate during the thermal huff and puff experiments through a single vertical well. The huff and puff method, also known as the cyclic steam stimulation (CSS), was accidentally discovered by Shell Oil Company in 1960 during a Venezuela recovery project and is widely used in the oil industry to enhance oil recovery.1820 The hot water, hot brine, or steam huff and puff method is a special form of the combination of depressurization and thermal stimulation methods for gas production from hydrate deposit. The change characteristics of the temperature, pressure, resistance ratio, and Received: December 21, 2010 Revised: March 8, 2011 Published: March 09, 2011 1650
dx.doi.org/10.1021/ef101731g | Energy Fuels 2011, 25, 1650–1658
Energy & Fuels
ARTICLE
Figure 1. Schematic of the three-dimensional experimental apparatus.
other related parameters during the huff and puff cycles are obtained, and the advantage and disadvantage of the thermal huff and puff method are analyzed.
2. EXPERIMENTAL SECTION 2.1. Experimental Apparatus. Figure 1 shows the schematic of the experimental apparatus. The experimental apparatus mainly consists of a reactor, a water bath, a back-pressure regulator, an aqueous solution injection system, a gas injection system, a water/gas separator, some measurement units, and a data acquisition system. The core component of the apparatus is a three-dimensional high-pressure reactor made of stainless-steel 316, with a pressure range up to 25 MPa. The inside of the reactor is cubic, with the edge length of 180 mm and effective volume of 5.8 L. The three-dimensional reactor, called the CHS, is placed in a water bath with a constant temperature. The reactor is equipped with multiple sets of the measuring points and wellheads, and the layout of the measuring points and the wellheads is divided into three layers, namely, top (A), middle (B), and bottom (C), with each layer having a total of 25 points. Panels a and b of Figure 2 show the distributions of the temperature and resistance measuring points of the different layers and production wellheads within the three-dimensional reactor. It can be seen that there are a total of 25 3 temperature measuring points, 12 3 resistance measuring points, and 1 3 central vertical wells along the centerline of the reactor, and the measuring points are evenly distributed in the reactor. In this experiment, the inlet for the heat injection is the B wellhead in the middle layer (B) along the centerline of the reactor, and the outlet for the gas and water production is the A wellhead in the top layer (A). Pressure is measured by the Trafag NAT8251.7425-type pressure sensor, with a measuring range of 025 MPa and an accuracy of (0.02 MPa. A pressure transducer at the outlet for the gas and water production is used to measure the outlet pressure, and another pressure transducer at the center of the bottom of the reactor is used to measure the pressure of the bottom of the hydrate-bearing layer. The temperature is measured by the Pt100 platinum resistor temperature sensor, with a measuring range from 20 to 200 °C and an accuracy of (0.1 °C. Resistance is measured by a H28 resistivity meter. Two gas flow meters, which are used to measure the cumulative gas injected into the CHS, the gas production rate, and the cumulative gas produced from the vessel, are both of D07-11CM, 010 L/min, (2% from the “Seven Star
Figure 2. Distributions of temperature and resistance measuring points and production wellhead of each layer within the three-dimensional reactor. 1651
dx.doi.org/10.1021/ef101731g |Energy Fuels 2011, 25, 1650–1658
Energy & Fuels
ARTICLE
Table 1. System Pressures and Corresponding Equilibrium Hydrate Decomposition Temperatures at Different Times of the Thermal Huff and Puff during the Third Cycle
Figure 3. Pressure and temperature profiles during the third huff and puff cycle. Company”. The thermometers, pressure transducers, and gas flow meters were calibrated using a mercury thermometer with a tolerance of (0.01 °C, a pressure test gauge with an error of (0.05%, and a wet gas meter with an accuracy of (10 mL/min, respectively. A metering pump “Beijing Chuangxintongheng” HPLC P3000A with a range of 50 mL/ min can withstand pressures of up to 30 MPa. An inlet liquid container with an inner volume of 10 L is used to contain the deionized water used in the experiments. To protect the metering pump from corrosion by the hot brine or the chemicals, three middle containers are used for the solution injection and the inner volume of each container is 4 L. A backpressure regulator (the pressure range of 030 MPa, (0.02 MPa) connected to the outlet of the CHS is used to control the pressure of the production well. A gas cylinder is used to provide the driving force of the back-pressure regulator. A balance, used to measure the mass of liquid produced from the CHS, is Sartorius BS 2202S, 02200 g, (0.01 g. The data acquisition system records the temperature, pressure, amount of the cumulative gas produced from the vessel, gas production rate, and liquid production rate. The liquid injection rate can be controlled by the metering pump, which is connected to the data acquisition system. In this work, the methane gas with its purity of 99.99% is used. 2.2. Experimental Methods. Quartz sand, with a quality of 8162 g, particle size from 300 to 450 μm, and porosity of approximately 48%, is tightly packed in the CHS as porous media. The system is emptied twice to remove the residual air and other impurities in the system. A total of 1537 mL of deionized water is injected to the CHS by the metering pump. The temperature of the water bath is set to a predetermined temperature required for the gas hydrate synthesis, which is 8.0 °C in the current research. A total of 13.4 mol of methane is then injected to pressurize the CHS to 20 MPa. The inlet and outlet valves of the CHS are closed to keep the system in a constant volume condition. When hydrate formation starts, the pressure inside the CHS decreases. After hydrate formation, the final pressure after hydrate formed decreases to 13.5 MPa. Using the model of Linga et al.,21 the hydrate saturation (the volume ratio of hydrate and available pore space) is calculated as approximately 25% before hydrate dissociation. While the water bath is maintained at a constant temperature (8 °C), the upper and lower covers are the isothermal boundary conditions. The water in the preheater is heated to 130 °C, and then the bypass valve is opened to preheat the pipelines with hot water. After preheating, the bypass valve is closed. Subsequently, the inlet valve is opened for the heat injection. The gas production pressure controlled by the back-pressure regulator is set as 6.5 MPa. Before the heat injection starts, the system temperature is 8.0 °C. Using the fugacity model by Li et al.,22 the
time (min)
system pressure (MPa)
equilibrium temperature (°C)
0
6.62
9.52
2
6.86
9.87
5
7.27
10.44
11
7.36
10.56
17 22
7.38 6.5
10.59 9.34
equilibrium hydrate dissociation pressure in the sediment at the working temperature of 8.0 °C is calculated, and the calculated value is 5.7 MPa. Therefore, the set production pressure is higher than the equilibrium pressure at this time. Subsequently, the heat injection starts by injecting hot water at 40 mL/min for 5 min, leading to a total of 200 mL. The inlet valve is closed after the heat injection, and the soaking starts, during which the system pressure rises slowly. When the pressure stops rising, the soaking stage comes to an end and the gas production stage starts. The outlet valve of the well is opened, and when the system pressure drops to the set production pressure, the outlet valve is turned off. At this point, the current cycle of the gas production finishes and the next cycle of thermal huff and puff experiment starts. After more than 10 cycles of the huff and puff process, the system is closed for more than 2 h and then the system pressure was released to atmospheric pressure gradually.
3. RESULTS AND DISCUSSION 3.1. Temperature Change in a Single Cycle of Huff and Puff. In the 10 cycles of thermal huff and puff, each cycle consists
of three stages: heat injection, soaking, and gas production. The heat transfer of a single huff and puff cycle is studied using the third cycle, and the other cycles follow similar characteristics. Hot water was injected from the central well 13B, and the heat flux was transferred to the surroundings via the flow and conduction through the porous media.23 Figure 3 shows the changes of the bottom and outlet pressures in the CHS for the third cycle of the thermal huff and puff, the temperatures of points 13B, 7B, and 1B, and the equilibrium hydrate decomposition temperature of the system over time, as seen in Figure 3. The bottom and outlet pressures are almost the same at any time because of the high porosity and permeability of the sediment, which can be described as the system pressure in the CHS. In addition, as shown, in the heat injection stage (05 min), the system pressure increases from 6.5 to 7.25 MPa rapidly. In the soaking stage (517 min), the system pressure increases slowly, and when the pressure no longer increases, the soaking stage comes to an end. In this process, the increase of the system pressure is approximately from 7.25 to 7.40 MPa. In the gas production stage (1722 min), the pressure decreases rapidly to approximately 6.5 MPa (the set production pressure). Meanwhile, Figure 3 shows the change of the equilibrium hydrate decomposition temperature corresponding to the system pressure calculated with the fugacity model given by Li et al.22 Table 1 shows the system pressure and the calculated corresponding equilibrium temperature at different times of the thermal huff and puff during the third cycle. The figure also shows that the temperatures of points 13B, 7B, and 1B change sequentially. The temperature of point 13B (being at the wellhead) increases along with the time, reaches the maximum at the end of the injection stage, and then gradually 1652
dx.doi.org/10.1021/ef101731g |Energy Fuels 2011, 25, 1650–1658
Energy & Fuels
ARTICLE
Figure 4. Spatial distribution of the temperature during the third huff and puff cycle.
decreases in the soaking and gas production stages. The temperature of point 7B starts to increase at the second minute during the heat injection, reaches its maximum at the second minute during the soaking, and then gradually decreases during the remaining time of the soaking and the gas production period. This is because the heat diffusion from the central point to the surroundings passes points 13B, 7B, and 1B sequentially, which leads to the sequential temperature change. The temperature gradually decreases from points 13B to 1B at the fixed time because of the heat-transfer consumption through porous media, heat consumption during the decomposition of the gas hydrates, and the heat loss from the reactor boundary made of stainless steel. In addition, it is noted from Figure 3 that the temperature of point 1B has little change during the huff and puff cycle and the temperature is lower than the equilibrium hydrate decomposition temperature. Thus, the driving force for the decomposition is zero, resulting in no hydrate decomposition at point 1B. Figure 4 shows the three-dimensional spatial temperature distribution of six different moments during the third huff and puff cycle. It can be seen from the figure that, centered at the central heat injection point, the heat flow spreads to the surroundings with time and eventually decays. As also shown in Figure 4, before the heat injection (0 min), the temperature at all points within the system remains almost the same and is close
to the environmental temperature. At 2 min after the heat injection, the temperature at the central point has risen and the heat has diffused to the surroundings. The injection ends at 5 min, when the temperature at the central point reaches the maximum and the temperature of the surroundings increases accordingly. The soaking stage occurs from 5 to 17 min. As suggested in the figure, at the 11th minute, the temperature of the surroundings continues to rise but the central temperature drops, indicating that the heat flow continuously expands and the heat dissipates through the boundary of the reactor. At the 17th minute, the expanding of heat flow almost stops and the decomposition of gas hydrate also almost stops, which means the end of the soaking stage. The gas production stage occurs from 17 to 22 min. During this period, the temperature of the regions far away from the well decreases slightly and the central temperature decreases to near ambient temperature, which is also the temperature at time 0. This is because the heat of the system is almost entirely consumed. 3.2. Temperature Change in Multicycles of Huff and Puff. Figure 5 shows the temperature distributions at the end of the 2nd, 4th, 6th, 8th, and 10th soaking stages. The region impacted by heat diffusion of the 2nd cycle of heat injection progresses within a small territory and almost does not reach the wall in the reactor, which is probably because most of the heat is 1653
dx.doi.org/10.1021/ef101731g |Energy Fuels 2011, 25, 1650–1658
Energy & Fuels
ARTICLE
Figure 5. Spatial distributions of temperatures at the ends of the 2nd, 4th, 6th, 8th, and 10th soaking stages.
Figure 6. Pressure profile during gas production using the huff and puff method.
concentrated in the center, mainly used for the hydrate decomposition in the central region, and the heat loss occurs through the boundary of the reactor. The region impacted by heat
diffusion of the 4th and 6th cycles continue to progress, and the volume affected by the heat gradually increases with the heat injection. The hydrate in the surroundings is also gradually decomposed because the heat continues to decompose the hydrate in the surroundings, and the heat loss starts through the boundary of the reactor. The region impacted by heat diffusion of the 8th and 10th cycles make little progress, probably because of the heat loss through the boundary of the reactor, which leaves no capability to progress to the surroundings and to decompose more hydrate. The injected energy reaches its largest impact region at this time. From panels e and f of Figure 5, we can conclude that there is a maximum of the region impacted by heat diffusion, which expands outward with the huff and puff cycles. 3.3. Pressure Change. Figure 6 shows the change of the system pressure with time in the thermal huff and puff production experiment. As shown, in Figure 6, in each cycle of the thermal huff and puff experiments, the system pressure increases remarkably in the heat injection stage, mainly because of emplacement of 200 mL of incompressible fluid in a container of a fixed volume. Meanwhile, the heat injection causes the system temperature in the CHS to be much higher than the equilibrium temperature under this pressure, which leads to gas production. The pressure increases slowly in the soaking stage. 1654
dx.doi.org/10.1021/ef101731g |Energy Fuels 2011, 25, 1650–1658
Energy & Fuels
ARTICLE
Figure 7. Gas recovered during the gas production stage in each cycle of thermal huff and puff.
The reason is that the incompressible fluid stops to inject, and the remarkable rise of the pressure during the heat injection stage means the relatively large increase of the corresponding equilibrium temperature, resulting in the obvious reduction of the temperature driving force for the hydrate decomposition and, furthermore, the reduction of the amount of gas produced in the soaking stage. Thus, the relatively low gas production process causes the slow increase of the system pressure, despite the continuous decomposition of the hydrate as a result of continuous heat diffusion in the soaking stage. When the pressure no longer increases, the soaking stage ends. In the gas production stage, with the release of the methane gas, the pressure decreases rapidly. Figure 7 shows the gas recovered during the gas production stage in each cycle of thermal huff and puff. It can also be seen from Figures 6 and 7 that, in a total of 10 cycles of thermal huff and puff experiments, the soaking time increases, the increase degree of the pressure during soaking decreases, and the amount of gas recovered during gas production decreases as the number of cycles increases, which is due to the fact that, as the number of cycles increases, the heat diffusion gradually expands toward the surroundings and, furthermore, the time, when the heat flux reaches the boundary of undissociated hydrate reservoir and dissociates the hydrate, is successively elongated. Thus, the corresponding soaking time is also successively elongated. In addition, the amount of hydrate dissociation successively reduces with the increase of the number of cycles, resulting in the reduction of the pressure increase degree during soaking and the amount of gas recovered during gas production. Eventually, as the region impacted by heat diffusion reaches the maximum influence, the pressure increases during soaking, and the gas recovered during gas production is close to 0, we believe that there is no more gas hydrate decomposition and the thermal huff and puff production of gas hydrate reaches the maximum production range. 3.4. Resistance Ratio Change. The resistance can be used to characterize the change of the gas hydrate reservoir.24 Because the resistivity of gas hydrate is greater than water, generally the resistance decreases as the hydrate decomposes. However, experimentally, the resistance is also affected by the temperature and water/gas flow in porous media. In the work, we use the ratio between the real-time resistance during the experiment and the
Figure 8. Resistance ratio and temperature profiles in the vicinity of the production well and near the edge of the vessel during gas production using the huff and puff method.
resistance before the experiment (referred to as the resistance ratio) as a characterization parameter. The resistance measuring points are divided into two groups: the near-well region and the far-from-well region. The near-well region is located around the central vertical well, including measuring points 7, 9, 17, and 19 in the three A, B, and C layers. The far-fromwell region is around the boundaries, including measuring points 2, 4, 6, 10, 16, 20, 22, and 24 in the three A, B, and C layers. Figure 8a shows the resistance ratio and temperature changes of measuring points 7B and 19B in the near-well region during the production. A comparison of the resistance ratios of the two measurement points shows that, at point 19B in the near-well region, during the period of the first 75 min, i.e., the first three cycles, the resistance ratio increases dramatically in a short period of time. This is probably due to the fact that considerable gas generated from the decomposition of a large amount of the hydrate fills the pores in the sediment, including those of the original and those left by the hydrate decomposition, resulting in the increase of the resistance. Afterward, mainly because a large amount of gas produced is released, the resistance decreases rapidly. Starting from 75 min, the experimental resistance ratio generally remains unchanged, with a regular fluctuation. The fluctuation is due to the temperature change during the thermal huff and puff and can be reversely correlated with the temperature change. At this stage, the resistance is mainly related to the 1655
dx.doi.org/10.1021/ef101731g |Energy Fuels 2011, 25, 1650–1658
Energy & Fuels
ARTICLE
Figure 9. Equilibrium temperature isotherm at different times of the thermal huff and puff during the third cycle.
temperature, which further indicates that the hydrate completely decomposes at point 19B. For the measuring point 7B in the near-well region, the resistance ratio increases and decreases dramatically during the period of the first 25 min of the experiment and, after 25 min, the overall trend of the resistance ratio change remains unchanged with regular fluctuations with the temperature, indicating that the hydrate at point 7B completely decomposes within the first 25 min. Figure 8b shows the changes of the resistant ratios of measuring points 6B and 20B in the far-from-well region during the production. It can be seen from the figure that, for the measuring point 6B, the resistance ratio does not change significantly within the first 20 min or the first cycle of thermal huff and puff, which is because the injected heat has not affected the far-from-well region. From 20 to 50 min, i.e., within the second and third cycle of thermal huff and puff, the overall resistance ratio tends to decrease mainly because of the hydrate decomposition. After that, the resistance ratio generally remains unchanged with a regular fluctuation caused by the temperature change during the thermal huff and puff, as shown in Figure 8b. The reason is that the hydrate no longer decomposes or maybe there is no hydrate left at this measuring point during the period.
For the measuring point 20B, as shown in Figure 8b, the resistance ratio during the whole thermal huff and puff process stays almost unchanged, probably because the injected heat has not arrived at point 20B, there is no hydrate decomposition at this point, or there is no gas hydrate at all at this point. Points 7B and 19B as well as points 6B and 20B are completely symmetrical, but the resistance changes are different, indicating that the diffusion of the injected heat is not completely isotropic when diffused from the center to the surroundings, which may be due to the difference in the local hydrate saturation, porosity of the sediment, or permeability of the sediment. The resistances of other points in the near-well and far-from-well regions at symmetrical locations show similar behaviors. 3.5. Moving Boundary Ablation. The hydrate decomposition is considered to be a moving boundary ablation problem.23 The moving boundary separates the decomposed zone containing gas and water from the undecomposed zone containing the hydrate. From the previous discussion, we know that, in every cycle of thermal huff and puff, the heat spreads out from the center and the temperature decreases from the center outward. In addition, the system pressure changes with time. Thus, the corresponding equilibrium hydrate decomposition temperature also changes 1656
dx.doi.org/10.1021/ef101731g |Energy Fuels 2011, 25, 1650–1658
Energy & Fuels with time, which can be calculated from the expression given by Li et al.22 The system pressure and the calculated corresponding equilibrium temperature of the third cycle are shown in Table 1. Figure 9 shows the three-dimensional isothermal surface under the equilibrium hydrate decomposition temperature at the different times in the third cycle of thermal huff and puff. The temperatures of the region surrounded by the isothermal surface are higher than the equilibrium temperature, and this region is one for gas hydrate decomposition. The temperature of the region outside the isothermal surface is lower than the equilibrium temperature and is not the hydrate decomposition region. Thus, we can approximately consider that the isothermal surface is a moving decomposition boundary. It can be seen from Figure 9 that, at 0 min, there is a small temperature region in the CHS, within which the temperatures are higher than the equilibrium temperature. This illustrates that there still is a small region for gas hydrate decomposition at the end of the last cycle of thermal huff and puff . It can be seen from Figure 9 that, in the process of the heat injection of 05 min, the isothermal surface rapidly expands. At 517 min is the soaking stage, within which the isothermal surface is continuously expanding for 511 min, indicating that the heat flow continuously expands outward in the period, while from 11 to 17 min, the isothermal surface gradually shrinks, because of the heat loss through the boundary of the reactor, which leads to a temperature decrease inside the CHS. At 1722 min is the gas production stage, in which the system pressure continuously decreases. It is noted that the isothermal surface at the 22th minute is similar to that at the 17th minute. That is to say, there is no more temperature region increasing for gas hydrate decomposition inside the CHS during the gas production stage. However, the isothermal surface at the 22th minute is larger than the isothermal surface at the 0th minute, which means that the region for gas hydrate decomposition at the end of the third cycle is larger than that at the end of the second cycle.
4. CONCLUSION In this work, the novel developed three-dimensional CHS for the production of gas hydrate is used to investigate the decomposition behaviors of methane hydrate during the thermal huff and puff experiments through a single vertical well. A total of 10 cycles of the thermal huff and puff experiments with a single vertical well are carried out for gas hydrate decomposition, using a novel developed three-dimensional CHS. The following conclusions are obtained: Each cycle of thermal huff and puff consists of three stages: heat injection, soaking, and gas production. The pressure rapidly increases in the heat injection stage and slowly increases in the soaking process. The injected heat spreads out from the injection point. The region impacted by heat diffusion enlarges as the number of huff and puff cycles increases and eventually reaches its largest region. After that, even if the heat huff and puff with one single well continues, the region impacted by heat diffusion of the system will not spread out further. Meanwhile, the injected heat does not diffuse isotropically. In addition, the hydrate decomposition process with heat injection is a moving boundary ablation process. ’ AUTHOR INFORMATION Corresponding Author
*Address: Key Laboratory of Renewable Energy and Gas Hydrate, Guangzhou Institute of Energy Conversion, Chinese
ARTICLE
Academy of Sciences, Guangzhou 510640, People’s Republic of China. Telephone: þ86-20-87057037. Fax: þ86-20-87034664. E-mail:
[email protected].
’ ACKNOWLEDGMENT This work was supported by the National Natural Science Foundation of China (Grants 51076155 and 51004089), the Chinese Academy of Sciences (CAS) Knowledge Innovation Program (Grant KGCX2-YW-3X6), and the Science and Technology Program of Guangdong Province (Grant 2009B050600006), which are gratefully acknowledged. ’ REFERENCES (1) Sean, W. Y.; Sato, T.; Yamasaki, A.; Kiyono, F. CFD and experimental study on methane hydrate dissociation. Part I. Dissociation under water flow. AIChE J. 2007, 53 (1), 262–274. (2) Makogon, Y. F.; Holditch, S. A.; Makogon, T. Y. Natural gashydrates—A potential energy source for the 21st century. J. Pet. Sci. Eng. 2007, 56 (13), 14–31. (3) Koh, C. A.; Sloan, E. D. Natural gas hydrates: Recent advances and challenges in energy and environmental applications. AIChE J. 2007, 53 (7), 1636–1643. (4) Castaldi, M. J.; Zhou, Y.; Yegulalp, T. M. Down-hole combustion method for gas production from methane hydrates. J. Pet. Sci. Eng. 2007, 56 (13), 176–185. (5) Li, X. S.; Wan, L. H.; Li, G.; Li, Q. P.; Chen, Z. Y.; Yan, K. F. Experimental investigation into the production behavior of methane hydrate in porous sediment with hot brine stimulation. Ind. Eng. Chem. Res. 2008, 47 (23), 9696–9702. (6) Makogon, T. Y.; Larsen, R.; Knight, C. A.; Sloan, E. D. Melt growth of tetrahydrofuran clathrate hydrate and its inhibition: Method and first results. J. Cryst. Growth 1997, 179 (12), 258–262. (7) Ahmadi, G.; Ji, C. A.; Smith, D. H. Production of natural gas from methane hydrate by a constant downhole pressure well. Energy Convers. Manage. 2007, 48 (7), 2053–2068. (8) Li, G.; Li, X. S.; Tang, L. G.; Zhang, Y. Experimental investigation of production behavior of methane hydrate under ethylene glycol injection in unconsolidated sediment. Energy Fuels 2007, 21 (6), 3388–3393. (9) Hirohama, S.; Shimoyama, Y.; Wakabayashi, A.; Tatsuta, S.; Nishida, N. Conversion of CH4-hydrate to CO2-hydrate in liquid CO2. J. Chem. Eng. Jpn. 1996, 29 (6), 1014–1020. (10) Hamaguchi, R.; Nishimura, Y.; Matsukuma, Y.; Minemoto, M.; Watabe, M.; Arikawa, K. Gas-liquid two-phase pipe flow analysis of methane hydrate recovery system using gas-lift system. Kagaku Kogaku Ronbunshu 2005, 31 (1), 68–73. (11) Moridis, G. J.; Collett, T. S.; Boswell, R.; Kurihara, M.; Reagan, M. T.; Koh, C.; Sloan, E. D. Toward production from gas hydrates: Current status, assessment of resources, and simulation-based evaluation of technology and potential. SPE Reservoir Eval. Eng. 2009, 12 (5), 745–771. (12) Holder, G. D.; Angert, P. F.; John, V. T.; Yen, S. A thermodynamic evaluation of thermal recovery of gas from hydrates in the earth. J. Pet. Technol. 1982, 34 (5), 1127–1132. (13) Roadifer, R. D.; Godbole, S. P.; Kamath, V. A. Thermal model for establishing guidelines for drilling in the arctic in the presence of hydrates. Proceedings of the 57th Annual California Regional Meeting; Society of Petroleum Engineers (SPE) of American Institute of Mining, Metallurgical, and Petroleum Engineers (AIME), Ventura, CA, 1987; SPE Paper 16361. (14) Liu, Y.; Strumendo, M.; Arastoopour, H. Simulation of methane production from hydrates by depressurization and thermal stimulation. Ind. Eng. Chem. Res. 2009, 48 (5), 2451–2464. (15) Selim, M. S.; Sloan, E. D. Hydrate dissociation in sediment. SPE Reservoir Eng. 1990, 5, No. 16859-7. 1657
dx.doi.org/10.1021/ef101731g |Energy Fuels 2011, 25, 1650–1658
Energy & Fuels
ARTICLE
(16) Ullerich, J. W.; Selim, M. S.; Sloan, E. D. Theory and measurement of hydrate dissociation. AIChE J. 1987, 33 (5), 747–752. (17) Sasaki, K.; Ono, S.; Sugai, Y.; Ebinuma, T.; Narita, H.; Yamaguchi, T. Gas production system from methane hydrate layers by hot water injection using dual horizontal wells. J. Can. Pet. Technol. 2009, 48 (10), 21–26. (18) Leaute, R. P.; Carey, B. S. Liquid addition to steam for enhancing recovery (LASER) of bitumen with CSS: Results from the first pilot cycle. J. Can. Pet. Technol. 2007, 46 (9), 22–30. (19) Sayegh, S. G.; Maini, B. B. Laboratory evaluation of the CO2 huff-n-puff process for heavy oil-reservoirs. J. Can. Pet. Technol. 1983, 22 (2), 32–32. (20) Vittoratos, E. Flow regimes during cyclic steam stimulation at Cold Lake. J. Can. Pet. Technol. 1991, 30 (1), 82–86. (21) Linga, P.; Haligva, C.; Nam, S. C.; Ripmeester, J. A.; Englezos, P. Gas hydrate formation in a variable volume bed of silica sand particles. Energy Fuels 2009, 23, 5496–5507. (22) Li, X. S.; Zhang, Y.; Li, G.; Chen, Z. Y.; Yan, K. F.; Li, Q. P. Gas hydrate equilibrium dissociation conditions in porous media using two thermodynamic approaches. J. Chem. Thermodyn. 2008, 40 (9), 1464–1474. (23) Selim, M. S.; Sloan, E. D. Heat and mass-transfer during the dissociation of hydrates in porous-media. AIChE J. 1989, 35 (6), 1049–1052. (24) Zhou, X. T.; Fan, S. S.; Liang, D. Q.; Wang, D. L.; Huang, N. S. Use of electrical resistance to detect the formation and decomposition of methane hydrate. J. Nat. Gas Chem. 2007, 16 (4), 399–403.
1658
dx.doi.org/10.1021/ef101731g |Energy Fuels 2011, 25, 1650–1658
