Multiscale characterization of shale pore-fracture system: Geological controls on gas transport and pore size classification in shale reservoirs

Chen, Yufei; Jiang, Changbao; Leung, Juliana Y.; Wojtanowicz, Andrew K.; Zhang, Dongming

doi:10.1016/j.petrol.2021.108442

Cited by 50 publications

(35 citation statements)

References 52 publications

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“…The most effective way to transform the original NMR T 2 spectrum to PSD is to use the following equation [ 21 – 23 , 25 ]:

2

where d is the pore diameter, ρ 2 is the surface relaxivity, F s is the dimensionless pore shape factor ( F s = 2 and 3 for cylindrical pores and spherical pores, respectively; in this work, F s = 2) and T 2 is the transverse relaxation time (in this work, T 2 = 16.25 nm ms −1 [ 22 ]). Equation (4.2) shows that short relaxation time represents small pore or medium pore and long relaxation time represents macropore.…”

Section: Resultsmentioning

confidence: 99%

“…The most effective way to transform the original NMR T 2 spectrum to PSD is to use the following equation [21][22][23]25]: royalsocietypublishing.org/journal/rsos R. Soc. Open Sci.…”

Section: Nmr Resultsmentioning

confidence: 99%

“…The unique ability of NMR makes it a key and novel laboratory analytical tool for shale research since NMR technique has the advantage of being both non-intrusive and non-destructive [21][22][23]. In the present study, we used the MacroMR12-150H-I analyser (figure 4) to detect the internal structure and PSD of the shale sample.…”

Section: Experimental Methodsmentioning

confidence: 99%

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Triaxial testing on water permeability evolution of fractured shale

Wang¹,

Zhang

2021

R. Soc. open sci.

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A sound understanding of the water permeability evolution in fractured shale is essential to the optimal hydraulic fracturing (reservoir stimulation) strategies. We have measured the water permeability of six fractured shale samples from Qiongzhusi Formation in southwest China at various pressure and stress conditions. Results showed that the average uniaxial compressive strength (UCS) and average tensile strength of the Qiongzhusi shale samples were 106.3 and 10.131 MPa, respectively. The nanometre-sized (tiny) pore structure is the dominant characteristic of the Qiongzhusi shale. Following this, we proposed a pre-stressing strategy for creating fractures in shale for permeability measurement and its validity was evaluated by CT scanning. Shale water permeability increased with pressure differential. While shale water permeability declined with increasing effective stress, such effect dropped significantly as the effective stress continues to increase. Interestingly, shale permeability increased with pressure when the pressure is relatively low (less than 4 MPa), which is inconsistent with the classic Darcy's theory. This is caused by the Bingham flow that often occurs in tiny pores. Most importantly, the proposed permeability model would fully capture the experimental data with reasonable accuracy in a wide range of stresses.

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“…The most effective way to transform the original NMR T 2 spectrum to PSD is to use the following equation [ 21 – 23 , 25 ]:

2

Section: Resultsmentioning

confidence: 99%

“…The most effective way to transform the original NMR T 2 spectrum to PSD is to use the following equation [21][22][23]25]: royalsocietypublishing.org/journal/rsos R. Soc. Open Sci.…”

Section: Nmr Resultsmentioning

confidence: 99%

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Triaxial testing on water permeability evolution of fractured shale

Wang¹,

Zhang

2021

R. Soc. open sci.

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“…These experiments were conducted using the MICROXCT-400 three-dimensional reconstruction imaging X-ray microscope. The method of CT scanning experiment is based on using X-rays to create a three-dimensional data set image of a sample by superimposing continuous two-dimensional cross-sections; in this case, the internal pore and fracture structure information can be clearly and intuitively reflected [34,35].…”

Section: Ct Scanning Experimentsmentioning

confidence: 99%

Mechanical Properties of Lamellar Shale Considering the Effect of Rock Structure and Hydration from Macroscopic and Microscopic Points of View

et al. 2022

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It is well known that the effect of shale hydration causes wellbore instability due to water phase invasion of drilling fluid to lamellar shale rich formations. This is because of that the mechanical properties (compressive strength, elastic modulus, etc.) of lamellar shale surrounding the borehole, which is rich in clay minerals, will decrease significantly after hydration. In this study, using the lamellar shale in the continental stratum of the southern Ordos Basin, the mechanical properties of lamellar shale were studied by compression tests considering the effect of lamellar structure and hydration from a macroscopic point of view. In addition, the mechanical mechanism was discussed combined with the CT scanning tests results from a microscopic point of view. The results demonstrate the following points. Lamellar shale has stronger anisotropy than bedding shale, the compressive strength (deviatoric stress) and elastic modulus of lamellar shale are both lower than those of bedding shale, and it is more prone to tension fracture. With the increase in the angle (β) between the lamina and the axial direction from 0° to 90°, the compressive strength of lamellar shale decreases when β < 30° and then increases, the elastic modulus of lamellar shale decreases greatly when β < 30° and then tends to flatten. With the increase in hydration time, the compressive strength and elastic modulus of lamellar shale both gradually decrease, and the rates of their decrements reduce. The mechanical properties of lamellar shale are more affected by hydration than those of bedding shale. The hydration of lamellar shale leads to the formation of new fractures and the expansion of existing fractures in the junction area between the laminae and rock matrix, resulting in easy tension fracture along the laminae of shale.

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“…Compared to the volumetric method, the result from the gravimetric method is more reliable, because it uses a high-precision magnetic levitation balance and can avoid the calculation of physical parameters. Based on these test methods, many corresponding shale gas adsorption theories and models are proposed, such as monolayer adsorption theory [6][7][8], multi-molecular layer adsorption theory [9,10], micropore filling theory [11][12][13], SLD adsorption theory [14][15][16][17], Ono-Kondo adsorption theory [18][19][20][21], and combined adsorption theory [22]. However, on the one hand, all these adsorption experimental conditions cannot satisfy the reservoir conditions with the increase of reservoir development depth from shallow to deep, especially pressure, usually lower than 40 MPa for experimental conditions but higher than 50 MPa for in situ conditions.…”

Section: Introductionmentioning

confidence: 99%

Molecular Simulation of Adsorption in Deep Marine Shale Gas Reservoirs

Chang¹,

Zhang²,

et al. 2022

Energies

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Deep marine shale gas reservoirs are extremely rich in the Sichuan basin in China. However, due to the in situ conditions with high temperature and high pressure (HTHP), in particular reservoir pressure being usually much higher than the test pressure, it is difficult to accurately clarify the adsorption behavior, as seepage theory plays an important role in shale gas reserves evaluation. Therefore, three kinds of sorbent, including illite, quartz and kerogen, and two simulation methods, containing the grand canonical ensemble Monte Carlo method and molecular dynamics method, are synthetically used to determine the methane adsorption behavior under HTHP. The results show that both absolute adsorption and excess adsorption decrease with the increase of temperature. When the pressure increases, the absolute adsorption increases quickly and then slowly, and the excess adsorption first increases and then decreases. The superposition of wall potential energy is strongest in a circular hole, second in a square hole, and weakest in a narrow slit. The effect of pore size increases with the decrease of the pore diameter. Under HTHP, multi-layer adsorption can occur in shale, but the timing and number of layers are related to the sorbent type.

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Multiscale characterization of shale pore-fracture system: Geological controls on gas transport and pore size classification in shale reservoirs

Cited by 50 publications

References 52 publications

Triaxial testing on water permeability evolution of fractured shale

Triaxial testing on water permeability evolution of fractured shale

Mechanical Properties of Lamellar Shale Considering the Effect of Rock Structure and Hydration from Macroscopic and Microscopic Points of View

Molecular Simulation of Adsorption in Deep Marine Shale Gas Reservoirs

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