Numerical simulation of gas production from hydrate deposits using a single vertical well by depressurization in the Qilian Mountain permafrost, Qinghai-Tibet Plateau, China
Highlights
► The in-situ testing date of gas hydrates in Qinghai-Tibet Plateau was used to simulate the depressurization process. ► The gas production potential of gas hydrate deposits with depressurization was simulated by using Tough + Hydrate. ► The gas production capacity and the water Production Rate were calculated under different condition.
Introduction
Natural gas hydrates (NGH) are solid compounds of natural gas molecules that are encaged within a crystal structure composed of water molecules. They resemble packed snow or ice [1] in physical appearance and burn easily; thus, they are also called “flammable ice”. As a type of potential and substantial future energy resource, the current estimates of the worldwide quantity of natural gas hydrates range between 1015 and 1018 m3 [2]. Even the most conservative estimates of the total quantity of gas trapped in hydrates may surpass by a factor of two the total fuel fossil reserves' energy content recoverable by conventional methods. In addition, gas hydrates have a number of industrial and technological applications. These applications include using hydrate as natural gas transport and storage materials [3], preconditioning of fuel gas mixture before combustion [4], [5], and CO2 capture technique in IGCC system [6] and in combustion effluent [7].
In nature, gas hydrates occur both in the permafrost regions and in the marine sediments in the oceans and deep lakes where pressure-temperature conditions are suitable and where sufficient methane is delivered to the zone of hydrate stability in the uppermost sediments [8]. Currently, there are mainly three methods to dissociate gas hydrates: depressurization [9], [10], [11], thermal stimulation [12], [13], [14] and inhibitor stimulation [15], which are all based on breaking the gas hydrate pressure-temperature equilibrium conditions. Moreover, there is also a novel method recovering methane from hydrate with gaseous carbon dioxide [16]. Of these, depressurization is thought to be the most effective method for hydrate dissociation due to its economic and environmental advantages. These years, the hydrate dissociation has become a hot point for research [17], [18], [19], [20]. Experiments and simulations have been undertaken for predicting the behavior of hydrate of hydrate dissociation in the sediment. Yoshihiro et al. [18] performed the experiments on the hydrate formation and dissociation in porous media through depressurization method. Li and Jiang et al. [19], [20] evaluated the gas production potential from hydrate deposits in the permafrost region by simulations, and analyzed the sensitivity of methane production rate from hydrate reservoir.
In recent years, breakthroughs have been made in the exploration of permafrost-associated gas hydrate accumulations within the circumarctic regions of the northern hemisphere, such as northern Alaska in the USA, the Mackenzie Delta-Beaufort Sea region in Canada, the West Siberian Basin in Russia, etc. [8], which all show evidence of gas hydrate deposits.
The Qinghai-Tibet Plateau permafrost in China has a vast expanse with a total area of up to 150 × 104 km2. In recent years, a series of geological, geophysical, and geochemical investigations were conducted in the Qinghai-Tibet Plateau permafrost that confirmed the favorable occurrence conditions and prospecting potential for gas hydrate deposits in this region [21] of which the Qilian Mountain permafrost is the most important target area [22]. In 2008 and 2009, the scientific gas hydrate drilling project in the Qilian Mountain permafrost was implemented in China, as shown in Fig. 1(a) [19]. To date, a total of four test wells have been completed with well depths of 182.23 m, 635.20 m, 765.01 m and 466.65 m in DK-1, DK-2, DK-3 and DK-4. For all four wells, the thicknesses of the frozen layers range from 95 m to 115 m with an average thickness of 105 m. In the DK-1, DK-2 and DK-3 wells, gas hydrates were observed directly within several intervals, and gas hydrate samples were obtained successfully. Gas hydrates were also observed in the DK-4 well, but no samples were recovered. In all four wells, a series of gas hydrate-associated anomalies were observed [23]. The gas hydrate-bearing core sample recovered from DK-3 and its burning phenomenon are shown in Fig. 1(b) [23].
Gas hydrates in the Qilian Mountain permafrost are characterized by a relatively thin permafrost layer, shallow buried depth, complex gas components and coal-bed methane origin [19]. On the surfaces of the broken sections of the drill core, ice-like gas hydrate crystals can be observed directly. These gas hydrate crystals occur in the fissures of siltstones, mudstones and oil shale in the form of thin layers, flakes and lumps, or in the pores of sandstones in the disseminated form [23]. Temperature conditions are very crucial to the existence of gas hydrates in the Qilian Mountain permafrost. The average annual permafrost ground temperature ranges from 272.15 to 270.15 K [21]. According to the field measurements, the thermal gradients within the frozen layer and below the frozen layer are 0.011–0.033 K/m and 0.028–0.051 K/m [21], [24], which favor the stable formation of gas hydrates.
Three hydrate-bearing layers have been discovered at the DK-3 drilling site at the depths of 133–156 m, 225–240 m and 366–396 m [23]. Li et al. [19] studied the gas production potential of the first hydrate-bearing layer when using a single horizontal well either by the huff and puff method. The gas and water production was the significant parameter during the hydrate dissociation. Li [19], [25] studied the gas production rate and the gas-to-water ratio when the hydrate dissociation. And Jiang [20] mainly analyzed the methane production rate from hydrate reservoir as well. On the other hand, depressurization is thought to be the most economic and environmental advantages method for hydrate dissociation. Therefore, in this study, we will investigate the third layer hydrate at the DK-3 drilling site in the Qilian Mountain permafrost using a single vertical well by depressurization to evaluate the gas production potential of the gas hydrate deposits in this region.
Section snippets
Modeling code
The parallel version of Tough + Hydrate (pT + H) was used to conduct the numerical simulations in this study. This code is a widely used gas hydrate simulator and is developed from TOUGH2 family of codes at the Lawrence Berkeley National Laboratory. It is exclusively used in the simulation of hydrate formation and decomposition under conditions typical of common natural CH4 hydrate deposit (i.e. in the permafrost and in deep ocean sediments). It can model the non-isothermal gas release, phase
CH4 production rate
Fig. 3 shows the CH4 production rate evolution of hydrate dissociation (QR) for the three different wellbore pressure cases (1 MPa, 1.5 MPa and 2.5 MPa) over time. As shown in the figure, the QR evolution for the three cases shows nearly the same trend, which is a rapid decline at the early stage of gas production, followed by a decreasing rate of decline. Among these cases, the hydrate dissociation time for Case 1 is the shortest, lasting only approximately 1715 days. This is mainly because
Conclusions
In this study, numerical simulations and quantitative analyzes on gas and water production characteristics have been conducted for gas hydrate deposits at the Qilian Mountain permafrost DK-3 drilling site in the Qinghai-Tibet Plateau, China using a single vertical well by depressurization. Based on the simulation results, the following conclusions can be drawn:
- 1.
During the hydrate dissociation process, QR, QPT and QPG all reduce significantly. The majority of the gas production is from the output
Acknowledgment
This study has been supported by State Key Development Program for Basic Research of China (Grant No. 2009CB219507), National Natural Science of China (Grant No. 51006017), National High Technology Research and Development Program of China (Grant No. 2006AA09209-5) and Natural Science Foundation of China (Grant No. 50736001).
References (32)
- et al.
Hydrate-based pre-combustion carbon dioxide capture process in the system with tetra-n-butyl ammonium bromide solution in the presence of cyclopentane
Energy
(2011) - et al.
Hydrate-based CO2 (carbon dioxide) capture from IGCC (integrated gasification combined cycle) synthesis gas using bubble method with a set of visual equipment
Energy
(2012) - et al.
Production of natural gas from methane hydrate by a constant downhole pressure well
Energy Convers Manage
(2007) - et al.
Recovery of methane from hydrate reservoir with gaseous carbon dioxide using a three-dimensional middle-size reactor
Energy
(2012) - et al.
Pressure and temperature preservation techniques for gas-hydrate-bearing sediments sampling
Energy
(2011) - et al.
Numerical simulation of gas production potential from permafrost hydrate deposits by huff and puff method in a single horizontal well in Qilian Mountain, Qinghai province
Energy
(2012) - et al.
Sensitivity analysis of gas production from Class I hydrate reservoir by depressurization
Energy
(2012) - et al.
Gas hydrate occurrences in the Qilian Mountain permafrost, Qinghai Province, China
Cold Regions Sci Technol
(2011) - et al.
Production behavior of methane hydrate in porous media using huff and puff method in a novel three-dimensional simulator
Energy
(2011) - et al.
Clathrate hydrates of natural gases
(2007)
TOUGH+HYDRATE v1.1 user's manual: a code for the simulation of system behavior in hydrate-bearing geologic media
Formation enhancement of methane hydrate for natural gas transport and storage
Energy
Pre-combustion capture of carbon dioxide in a fixed bed reactor using the clathrate hydrate process
Energy
Liquid CO2 droplet extraction from gases
Energy
Natural gas hydrate in oceanic and permafrost environments
Depressurization-induced gas production from class 1 hydrate deposits
SPE Reservoir Eval Eng
Cited by (120)
Research on productivity of stimulated natural gas hydrate reservoir
2024, Renewable EnergyMolecular simulation study on carbon dioxide replacement in methane hydrate near the freezing point
2024, Gas Science and EngineeringExperimental investigation on the propagation of hydraulic fractures in massive hydrate-bearing sediments
2023, Engineering Fracture MechanicsProbing the mechanism of salts destroying the cage structure of methane hydrate by molecular dynamics simulation
2023, Geoenergy Science and Engineering