Research on stress-sensitivity of fractured porous media

Liu, Yuetian; Peng, Yu; Ding, Zupeng

doi:10.1016/j.petrol.2018.07.068

Cited by 8 publications

(4 citation statements)

References 20 publications

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“…Because of the stress sensitivity of low permeability and tight reservoir, more and more attention has been paid to the study of reservoir stress sensitivity, especially in the field of low permeability and micro-fracture developed reservoirs. A lot of literature has been published in recent years (Zhang et al 2014(Zhang et al , 2019Dou et al 2016;McKee et al 1988;Meng et al 2015;Liang et al 2016;Liu et al 2018;Boer et al 1992;Tang et al 2013;Li et al 2009;Meng et al 2015).…”

Section: Introductionmentioning

confidence: 99%

The study on experimental method of fluid stress sensitivity of low permeability in tight reservoir

Xiao

Liu

Shao

et al. 2021

J Petrol Explor Prod Technol

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According to the industry standard, low permeability and tight reservoir are highly stress-sensitive in laboratory tests. However, this phenomenon has not been effectively confirmed in the field production test. For this reason, a method to measure stress sensitivity by axial loading is proposed. By loading fixed axial stress, the measurement method achieves the effect of equivalent preloading fluid pressure. Meanwhile, the equivalent theoretical curve can be obtained by translating the curve. Through this method, the stress sensitivity of the core with microfracture is studied. According to the results, the stress sensitivity of the cores can be divided into two stages: the first stage is the non-opening stage of microfractures, in which the stress sensitivity is weak; the second stage is the opening stage of microfractures, in which the stress sensitivity increases sharply. When the permeability changes significantly, the corresponding pressure is the microfracture's opening pressure. In addition, if the abscissa of the experimental results corresponds to the field production data, the field stress sensitivity curve of the field reservoir can be obtained. Conventional stress sensitivity test shows that the four cores in the study block exhibit medium to strong stress sensitivity. According to the stress sensitivity curve analysis after curve translation, the stress sensitivity of the reservoir is about 25% in the elastic production stage, which is classified as weak stress sensitivity. This conclusion can effectively support the phenomenon of the unobvious stress sensitivity in the field production of low permeability and tight reservoirs.

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Section: Introductionmentioning

confidence: 99%

The study on experimental method of fluid stress sensitivity of low permeability in tight reservoir

Xiao

Liu

Shao

et al. 2021

J Petrol Explor Prod Technol

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“…At the initial stage of production, most fractures are keeping open and act as the high-speed way for oil and gas transportation. With the continuous production and the decrease of formation pressure, some fractures are closing and the high-speed access to the production well is gradually cut off, resulting in a significant reduction in reservoir permeability and well production [7,8]. erefore, it is of great theoretical and practical significance to investigate the stress sensitivity of fractured tight reservoirs.…”

Section: Introductionmentioning

confidence: 99%

An Experimental Study on Stress Sensitivity of Tight Sandstones with Different Microfractures

Zhao

Yang

Wang

et al. 2020

Advances in Civil Engineering

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Aiming at the stress sensitivity problem of tight reservoirs with different microfractures, the cores of H oilfield and J oilfield with different microfractures were obtained through the fractures experiment, so as to study the change of gas permeability in tight sandstone core plug during the change of confining pressure. Besides, we use the nuclear magnetic resonance (NMR) spectra of the core before and after saturation to verify whether the core has been successfully fractured. Based on Terzaghi’s effective stress principle, the permeability damage rate (D) and the stress sensitivity coefficient (Ss) are used to evaluate the stress sensitivity of the core, which show consistency in evaluating the stress sensitivity. At the same time, we have studied the petrological characteristics of tight sandstone in detail using thin section (TS) and scanning electron microscope (SEM). The results show that the existence of microfractures is the main factor for the high stress sensitivity of tight sandstone. In addition, because of the small throat of the tight reservoir core, the throat closes when the overlying stress increases. As a result, the tight sandstone pore size is greatly reduced and the permeability is gradually reduced. Therefore, in the development of tight reservoirs, we should not only consider the complex fracture network produced by fracturing, but also pay attention to the permanent damage of reservoirs caused by stress sensitivity.

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“…Many scholars [11][12][13][14][15][16] have studied the relationship between the permeability and stress of conventional oil and gas reservoirs and have obtained remarkable results. Wu et al [17] studied the factors influencing the stress sensitivity of shale by considering the overlying formation pressure.…”

Section: Introductionmentioning

confidence: 99%

“…The factors that can affect the stress sensitivity of shale were also investigated by some scholars. Liu et al [16] proposed a zero-stress model that is applicable after the failure of the elastic fracture model. Wang et al [20] investigated the velocity sensitivity of a lignite reservoir under different stresses through the orthogonal experiments.…”

Section: Introductionmentioning

confidence: 99%

Investigation on the Influence of Water-Shale Interaction on Stress Sensitivity of Organic-Rich Shale

et al. 2019

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Shale reservoirs are characterized by low permeability and natural fractures. In the process of reservoir development, the working fluid enters the reservoir. This may result in the formation of new fractures or expansion of natural fractures. When shale reservoirs are exploited, the fluid pressure in the fracture or pore is reduced. This destroys the stress balance of the reservoir, produces stress sensitivity damage, and reduces the reservoir permeability. Organic-rich shale from the Yanchang Formation, Chang 7 Member of the Ordos Basin, was selected for core flow experiment with helium. The effects of the type of brine, salinity, and soaking time on the stress sensitivity of an organic-rich shale reservoir were investigated. The acoustic characteristics were also investigated to study the effect of interactions between water and shale on stress sensitivity. The experimental results demonstrate that the interactions of water and shale increase the permeability of shale and reduce its stress sensitivity. Furthermore, when the permeability of the shale is excessively low, the stress sensitivity is high. In the acoustic studies, a higher attenuation coefficient of the acoustic wave corresponds to a larger variation in the shale structure and thus a larger permeability of the shale and smaller stress sensitivity coefficient. Whereas there is no apparent effect of the salt water type on the stress sensitivity, higher salinity levels cause higher stress sensitivity. After reacting with 15000 mg/L brine, the stress sensitivity coefficient of shale did not decrease significantly compared with that before action, all of which were above 0.97. However, after reacting with distilled water or 5000 mg/L brine, the stress sensitivity coefficient of shale decreased significantly, and all of them decreased to less than 0.9. Longer water exposures, corresponding to an increased duration of water-shale interactions, result in higher impacts on the stress sensitivity of shale. After 6 hours of shale-brine interaction, the stress sensitivity coefficient of shale is as high as 0.93, while after 48 hours of shale-brine interaction, the stress sensitivity coefficient of shale is reduced to 0.88. This study provides a highly effective reference with regard to the influence of the working fluid on the reservoir during drilling operations and the study of reservoir characteristics after fracturing.

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Research on stress-sensitivity of fractured porous media

Cited by 8 publications

References 20 publications

The study on experimental method of fluid stress sensitivity of low permeability in tight reservoir

The study on experimental method of fluid stress sensitivity of low permeability in tight reservoir

An Experimental Study on Stress Sensitivity of Tight Sandstones with Different Microfractures

Investigation on the Influence of Water-Shale Interaction on Stress Sensitivity of Organic-Rich Shale

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