Effects of mineralogy on pore structure and fluid flow capacity of deeply buried sandstone reservoirs with a case study in the Junggar Basin

Qiao, J.C.; Zeng, Jianhui; Ma, Yong; Jiang, Shu; Feng, Song; Hu, Huiting

doi:10.1016/j.petrol.2020.106986

Cited by 20 publications

(10 citation statements)

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“…Overall, the permeability of 83.3% samples is less than 1 mD. Tight sandstone reservoirs are generally low-porosity and low-permeability reservoirs which are not conducive to oilfield development. ,, …”

Section: Characteristics and Methodsmentioning

confidence: 97%

“…According to the principle of pore radius calculation of NMR, the relaxation time, relaxation rate, and rock specific surface area are related. − , The relationship between the relaxation time and pore radius is as follows where ρ is the surface relaxivity, S is the cores surface area, and V is the cores volume. The relationship between the radius and surface area is established by the ratio of surface area to volume. where F s is the shape factor.…”

Section: Characteristics and Methodsmentioning

confidence: 99%

“…Because the shape factor F s is a constant, surface relaxivity ρ is only related to the properties of the pore surface. Therefore, there is a constant relationship between the pore radius and relaxation time. ,, In NMR technology, the cutoff value T 2c is usually defined as the boundary point between the movable fluid saturation and bound fluid saturation. The schematic diagram is shown in Figure .…”

Section: Characteristics and Methodsmentioning

confidence: 99%

“…Because of the cementation of the minerals and the tamping effect of deep burial, the heterogeneity around the pores is strong, and the cementation of quartz, carbonate, and clay minerals is obvious. , Some reservoirs have obvious microcracks (Figure d). The pore structure is affected by the sedimentary environment, and the geological structure has a greater impact on the pore structure. ,, …”

Section: Characteristics and Methodsmentioning

confidence: 99%

“…The number of microscopic pores in tight sandstone is huge, and the pore structure is complicated and disordered; therefore, there may be a large amount of pore fluid that cannot flow. , In actual exploitation, movable fluid is of great value for the development of reservoirs. Movable fluid saturation can better reflect the physical characteristics and seepage laws of tight sandstone. − …”

Section: Introductionmentioning

confidence: 99%

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Effects of Microstructure and Rock Mineralogy on Movable Fluid Saturation in Tight Reservoirs

et al. 2020

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A large amount of injected fracturing fluid is retained in tight reservoirs, leading to low flowback efficiency (less than 30%). It may be related to low fluid movability in tight reservoirs, which is influenced by the complex pore structure and mineral composition. However, effects of microstructure and rock mineralogy on movable fluid saturation in tight reservoirs have not been studied clearly. The tight sandstone cores from the Ordos Basin, China, are analyzed by conducting a series of experiments, including routine petrophysical measurements and X-ray diffraction, scanning electronic microscopy, and nuclear magnetic resonance (NMR) experiments. The quantitative analysis of the pore structure is carried out based on the fractal theory. The results show that NMR T 2 distribution is divided into four types. For the T 2 spectrum (0 < β < 1) with a low left peak and a high right peak, the movable fluid saturation is 60.7% on average. Quartz has a positive correlation with movable fluid saturation, and clay minerals have a negative correlation with movable fluid saturation. It is caused by the high wettability of quartz and the strong cementation of clay minerals. Fractal dimension D mov has a negative correlation with movable fluid saturation. The complex structure and irregular shape of tight sandstone reduce the movable fluid saturation. Movable fluid mainly comes from macropores whose relaxation time is greater than 10 ms. In addition, the movable fluid porosity of the cores has obvious differences, especially in the macropores. Several studies have shown that the microscopic pore structure and mineral composition of tight sandstone are the key factors that determine the content of movable fluid in the tight reservoir.

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Section: Characteristics and Methodsmentioning

confidence: 97%