Effect of pore water on the depressurization of gas hydrate in clayey silt sediments

Wang, Xiaochu; Sun, Youhong; Peng, Sen; Wang, Yuanqi; Li, Shengli

doi:10.1016/j.jngse.2022.104836

Cited by 11 publications

(7 citation statements)

References 34 publications

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“…NH 4 Cl, a commonly used inorganic salt clay stabilizer, has excellent antiswelling effect. The injection of NH 4 Cl reduces the spacing between clay mineral crystals and decreases the thickness of the hydration film of clay particles . Besides, the process of hydrate decomposition is often accompanied by heat absorption.…”

Section: Resultsmentioning

confidence: 99%

“…The fracturing stage was considered complete when the total volume of injected fracturing fluid reached a preset value. Before the depressurization stage started, the pressure of the backpressure valve was set to 0.5 MPa (the phase equilibrium pressure of hydrate is 3.5 MPa in 276.2 K). Previous studies have demonstrated excellent gas production performance in clayey silt sediments at this decomposition pressure . Then, the valve 2 was opened, and the hydrates started to decompose under the effect of the pore pressure drop.…”

Section: Experimental Materials and Methodologymentioning

confidence: 95%

“…The injection of NH 4 Cl reduces the spacing between clay mineral crystals and decreases the thickness of the hydration film of clay particles. 5 Besides, the process of hydrate decomposition is often accompanied by heat absorption. As the temperature decreases, the solubility of NH 4 Cl decreases, causing NH 4 Cl particles to crystallize and precipitate (Figure 23).…”

Section: Gas Production Enhancement Via Hydraulicmentioning

confidence: 99%

“…Previous studies have demonstrated excellent gas production performance in clayey silt sediments at this decomposition pressure. 5 Then, the valve 2 was opened, and the hydrates started to decompose under the effect of the pore pressure drop. During the decomposition of hydrates, the temperature and pressure conditions were monitored dynamically by temperature thermocouples and pressure sensors, respectively, and the gas production rate and gas production volume were monitored by a gas flow meter.…”

Section: Introductionmentioning

confidence: 99%

“…Low gas production rates and poor seepage capacity always occur in the depressurization of marine gas hydrate, indicating a large gap in commercial production. − Hydraulic fracturing, as the most widely used low-permeability reservoir stimulation, is an effective solution to increase single-well production for low-permeability oil and gas reservoirs. − It has been proved to be a highly effective method for constructing gas seepage channels and expanding the extraction area in the mining of shale gas, tight gas, and coalbed methane. − However, it is still in the preliminary stage when it comes to the application in hydrate reservoirs. Some researchers have made a few efforts (Table ).…”

Section: Introductionmentioning

confidence: 99%

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Experimental Study on the Depressurization of Methane Hydrate in the Clayey Silt Sediments via Hydraulic Fracturing

et al. 2023

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Poor seepage capacity always occurs in the clayey silt hydrate reservoir, making it more difficult to achieve depressurization. Hydraulic fracturing is an important means of enhancing reservoir seepage and increasing gas production rates. In this work, a series of depressurization experiments were performed in a triaxial hydraulic fracturing apparatus. The samples were prepared according to the physical parameters of samples obtained from the South China Sea. The fracturing behavior and gas production characteristics of methane hydrate-bearing sediments were investigated. The effects of hydrate saturation, fracturing fluid properties, and in-situ stress on fracturing behavior were analyzed. It was found that it was feasible to be fractured for sediments with low hydrate saturation (S h < 0.30), and the fracture initiation pressure was positively correlated with the hydrate saturation. The results showed that medium-viscosity fracturing fluid had excellent flow and filtration loss reduction, which were beneficial to the maintenance of fractures inside sediments. The in-situ stress difference determined the direction of fracture propagation, which was always along the vertical direction of the minimum principal stress. Besides, the gas production enhancement and permeability improvement by hydraulic fracturing were evaluated. The average gas production rate and peak rate in the fractured run were 3.01 times and 5.84 times of those in the unfractured run, respectively. To further enhance the seepage capacity, the inorganic salt-based clay stabilizer solution was added to the fracturing fluid. The results showed that the permeability of the sediments fracturing with NH 4 Cl was 3.07 times of that in the unfractured run due to the inhibition of the hydration swelling of clay particles. The results are valuable to provide a basic understanding and suggestions for the application of hydraulic fracturing in gas hydrate reservoirs.

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Section: Resultsmentioning

confidence: 99%

Section: Experimental Materials and Methodologymentioning

confidence: 95%

Section: Gas Production Enhancement Via Hydraulicmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%