Irreducible water distribution from nuclear magnetic resonance and constant-rate mercury injection methods in tight oil reservoirs

Chen, Meng; Li, Min; Zhao, Jinzhou; Kuang, Yan

doi:10.1504/ijogct.2018.090972

Cited by 12 publications

(6 citation statements)

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“…Irreducible water is negligible in the Poiseuille formula, but it is essential to calculate the resistivity parameters. This is because the irreducible water may not flow in a two-phase flow but can conduct electricity. − The model provides theoretical support for the study of the relationship between rock electrical properties and relative permeability. However, whether the theoretical model is suitable for the study of the response law of rock electricity and relative permeability in tight sandstone gas reservoirs with complex pore-throat structures has not been verified experimentally.…”

Section: Introductionmentioning

confidence: 89%

Research on the Relationship between Electrical Parameters and Relative Permeability of Tight Sandstone

Zhao

Song

et al. 2022

ACS Omega

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The relationship between the electrical properties and relative permeability of tight sandstones with complex pore-throat structures is still unclear. In this study, a relationship model between the electrical parameters and pore-throat structure and the relative permeability of tight sandstone based on experimental data was established by combining theoretical derivation and experimental comparison. The model has typical three-terminal element characteristics. Porosity had little effect on relative permeability, whereas saturation index had a significant control effect on relative permeability. The relative permeability curve deduced based on the electrical parameters was quite different from the experimental fitting curve. Because irreducible water could conduct electricity but not flow, the relative permeability of the gas phase derived from the theory was higher than the experimental one, while the relative permeability of the water phase was lower. The isotonic point saturation of the phase permeability curve derived from the rock electrical parameter theory was larger than that obtained from the experiment. This research could help us obtain accurate relative permeability curves through electrical parameters and provide a basis for the fine evaluation of tight sandstone two-phase flow.

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Section: Introductionmentioning

confidence: 89%

Research on the Relationship between Electrical Parameters and Relative Permeability of Tight Sandstone

Zhao

Song

et al. 2022

ACS Omega

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“…A schematic diagram of the centrifuge is shown in Figure b. During centrifugation, the corresponding centrifugal force can be calculated based on the equation , where p c i is the centrifugal force, MPa, L is the length of the sample, cm, R is the external rotation radius, cm, Δρ is the density difference between water and air, g/cm 3 , and RPM is the rotational speed, r/min. In our experiment, R = 10 cm and Δρ = 0.999 g/cm 3 .…”

Section: Methodsmentioning

confidence: 99%

“…During gas/oil production the imbibed fracturing water is displaced by gas or oil until only irreducible water remains. This process can be simulated by centrifugation or gas displacement in the laboratory. − The NMR technique has also been performed on core samples to investigate the changing fluid distributions; − furthermore, the irreducible water saturation and drainage rate were calculated based on the area ratio of the NMR T 2 spectra for different pore–throat spaces in the core samples. Lyu et al studied the movable fluid distribution in tight sandstones based on the centrifuge and NMR experiments.…”

Section: Introductionmentioning

confidence: 99%

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Differences in the Fluid Characteristics between Spontaneous Imbibition and Drainage in Tight Sandstone Cores from Nuclear Magnetic Resonance

et al. 2018

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As the water injected during hydraulic fracturing is imbibed and then displaced in the matrix of tight reservoirs, it is meaningful to characterize the fluid distributions and percolation dynamics during these two processes as they significantly affect production. In this study, 6 tight sandstone cores from the Chinese Ordos Basin were selected to experimentally study the fluid seepage and distributions during spontaneous imbibition and drainage using a low-field nuclear magnetic resonance (NMR) core analysis unit. Dry cores were first tested via cocurrent imbibition and then centrifuged from fully saturated to irreducible water saturation to simulate the imbibition and drainage processes, respectively. The weights and T 2 spectra were measured concurrently for each step. The results showed that the volume of imbibed water increased rapidly during the first 3000 min and reached a constant value at the end of the experiment; the final imbibition water saturation S w i m ranged from 48.52% to 89.20%. The irreducible water saturation S w i r was reached after a centrifuge speed of 10 000 r/min and varied from 40.46% to 53.28%. The gas and water relative permeabilities were estimated by combining the T 2 spectra for different water saturations, which indicated the effect of the capillary force and pore–throat structure on the different fluid seepage characteristics during spontaneous imbibition and drainage. The T 2 time was converted to the corresponding pore–throat radius by combining the fully water-saturated T 2 spectra and pore distributions from a constant-rate mercury injection. Micropores of 0–2 μm were identified as the dominant pore spaces for imbibed water during spontaneous imbibition and the water remained after centrifugation, whereas a small amount of water was imbibed or remained in pores larger than 20 μm. The physical properties, microstructure, and dispersed clay minerals were considered to be the three dominant factors of the fluid dynamics and distribution differences, and the effects were stronger during spontaneous imbibition.

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“…In addition, the fluid viscosity at the interface region is higher than that at the bulk region due to the pore wall effect. Tight reservoirs have abundant irreducible water [17,18], and the medium in these reservoirs exhibits stress sensitivity [4]. Thus, it is challenging to investigate the flow capability, which is characterized by permeability, of fluid flowing in tight reservoirs while considering the effects of multiple factors, such as fluid/oil slip, irreducible water, stress sensitivity, and the pore wall effect.…”

Section: Introductionmentioning

confidence: 99%

A Fractal Permeability Model of Tight Oil Reservoirs Considering the Effects of Multiple Factors

Cui

Yang

et al. 2022

Fractal Fract

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The prediction of permeability and the evaluation of tight oil reservoirs are very important to extract tight oil resources. Tight oil reservoirs contain enormous micro/nanopores, in which the fluid flow exhibits micro/nanoscale flow and has a slip length. Furthermore, the porous size distribution (PSD), stress sensitivity, irreducible water, and pore wall effect must also be taken into consideration when conducting the prediction and evaluation of tight oil permeability. Currently, few studies on the permeability model of tight oil reservoirs have simultaneously taken the above factors into consideration, resulting in low reliability of the published models. To fill this gap, a fractal permeability model of tight oil reservoirs based on fractal geometry theory, the Hagen–Poiseuille equation (H–P equation), and Darcy’s formula is proposed. Many factors, including the slip length, PSD, stress sensitivity, irreducible water, and pore wall effect, were coupled into the proposed model, which was verified through comparison with published experiments and models, and a sensitivity analysis is presented. From the work, it can be concluded that a decrease in the porous fractal dimension indicates an increase in the number of small pores, thus decreasing the permeability. Similarly, a large tortuous fractal dimension represents a complex flow channel, which results in a decrease in permeability. A decrease in irreducible water or an increase in slip length results in an increase in flow space, which increases permeability. The permeability decreases with an increase in effective stress; moreover, when the mechanical properties of rock (elastic modulus and Poisson’s ratio) increase, the decreasing rate of permeability with effective stress is reduced.

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Irreducible water distribution from nuclear magnetic resonance and constant-rate mercury injection methods in tight oil reservoirs

Cited by 12 publications

References 0 publications

Research on the Relationship between Electrical Parameters and Relative Permeability of Tight Sandstone

Research on the Relationship between Electrical Parameters and Relative Permeability of Tight Sandstone

Differences in the Fluid Characteristics between Spontaneous Imbibition and Drainage in Tight Sandstone Cores from Nuclear Magnetic Resonance

A Fractal Permeability Model of Tight Oil Reservoirs Considering the Effects of Multiple Factors

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