scholarly journals Mechanism of Permeability Evolution for Reservoir Sandstone with Different Physical Properties

Geofluids ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-16 ◽  
Author(s):  
Xianshan Liu ◽  
Ming Xu ◽  
Ke Wang
Keyword(s):  
Physical Properties ◽  
Water Pressure ◽  
Great Influence ◽  
Confining Pressure ◽  
Permeability Evolution ◽  
Mechanical Coupling ◽  
Reservoir Permeability ◽  
Reservoir Sandstones ◽  
Permeability Increase ◽  
Distinct Features

Permeability of sandstones with different properties taken from Chongqing reservoirs has been measured and deeply discussed under increasing deviatoric stress. Corresponding to the distinct features in the stress-strain behaviors, the permeability of sandstones is found to evolve with a clear permeability decrease in the initial closure region, a constant permeability value in the elastic region, a permeability increase in the crack initiation and propagation region, a sharp permeability increase in the crack growth region, and a decrease permeability in the residual stage. The results also show that the variation patterns of permeability are similar for two reservoir sandstones under combination of confining pressure and water pressure; however, the strength and permeability are smaller for the sandstone with mud than that without mud, deeply indicating that mud-like materials have a relatively great impact on the mechanical properties and permeability, so mud components cannot be ignored for prediction of reservoir permeability. Furthermore, a statistical damage constitutive model considering hydraulic-mechanical coupling process is presented to calculate the damage variable D, illustrating that larger water pressure will result in a relatively smaller damage variables D and corresponding maximum, which explains that the permeability increases more rapidly and is larger for the sandstone without mud than that with mud, and sandstone damage related to corresponding circumferential crack strain and permeability has been investigated, also implying the evolution mechanism of permeability for two sandstones with different physical properties. Therefore, it is worth pointing out that rock physical properties have a great influence on the reservoir permeability under complex extraction conditions and cannot be ignored, which is necessary to improve the recovery ratio and productivity.

scholarly journals Experimental Investigation on the Stress-Dependent Permeability of Intact and Fractured Shale

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Yongxiang Zheng ◽  
Jianjun Liu ◽  
Yichen Liu ◽  
Di Shi ◽  
Bohu Zhang
Keyword(s):  
Pore Pressure ◽  
Confining Pressure ◽  
Fracture Network ◽  
Permeability Evolution ◽  
Matrix Permeability ◽  
Reservoir Permeability ◽  
Slippage Effect ◽  
Before And After ◽  
Shale Reservoir ◽  
Stress Dependent

The permeability of shale is extremely low. Therefore, the shale reservoir needs fracturing. The fracture network by fracturing can increase the permeability in a stimulated shale reservoir. To understand the permeability evolution in the stimulated shale reservoir, this study measured the permeability of intact and fractured shale samples with different pore pressure and confining pressure by the transient pulse test. And the differences between the two kinds of samples in permeability were analyzed. The results show that permeability magnitude of fractured shale is increased by 5 orders compared to the intact shale. It means that fracture networks after fracturing can effectively improve the permeability. Besides, the change in matrix permeability is the result of the combined effect of slippage effect and matrix deformation. At low pore pressure, the influence of slippage effect is more significant. Based on the results, an improved exponential function was established to describe the relationship between permeability and effective stress of shale matrix. Moreover, the permeability of fractured shale is still bigger than that of the shale matrix when the confining pressure is larger than pore pressure. This paper provides theoretical guidance for studying the evolution of reservoir permeability before and after fracturing.

scholarly journals Progressive Failure and Fracture Mechanism of Sandstone under Hydraulic-Mechanical Coupling

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Yingming Li ◽  
Gang Liu ◽  
Tao Qin ◽  
Zhupeng Jin ◽  
Chengxing Zhao ◽  
...  
Keyword(s):  
Pore Water ◽  
Fracture Mechanism ◽  
Pore Water Pressure ◽  
Progressive Failure ◽  
Water Pressure ◽  
Confining Pressure ◽  
Experimental Results ◽  
Type I ◽  
Volume Deformation ◽  
Mechanical Coupling

Hydraulic coupling often leads to progressive rock failure accidents. Mechanical tests were performed over a range of combined pore water pressure and confining pressure stress path conditions to study the progressive failure characteristics of sandstone under hydraulic-mechanical coupling and explore the crack initiation and pore water fracture mechanism. The closure stress and damage stress were determined by the axial deformation stiffness and volume deformation stiffness. The experimental results indicate that confining pressure is the main controlling factor in the crack propagation stage, and pore water pressure enhances crack evolution. With increasing effective confining pressure, the effective peak deviatoric stress strongly increases and the characteristic stress increases linearly. The initiation stress and damage stress decrease with increasing pore water pressure. The moduli in stages I, II, and III are similar to the law of the transverse and radial deformation ratio with notable differences in stage IV. The fracture trend angle was determined by the ratio of axial crack strain and radial crack strain. Compared with the experimental results, the internal cracks in the sandstone samples are mainly type-II cracks, and type-I cracks are also locally present. After stress damage, the cracks expand and extend at an angle close to the real fracture.

scholarly journals Experimental Investigation on the Evolution of Damage and Seepage Characteristics for Red Sandstone under Thermal-mechanical Coupling Conditions

2021 ◽  
Author(s):  
Haopeng Jiang ◽  
Annan Jiang ◽  
Fengrui Zhang
Keyword(s):  
High Temperature ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Effect Of Temperature ◽  
Permeability Evolution ◽  
Red Sandstone ◽  
Permeability Characteristics ◽  
Mechanical Coupling ◽  
Coupling Conditions ◽  
Rock Stability

Abstract Rock masses in underground space usually experience the coupling of high-temperature field, stress field and seepage field, which gives them complex mechanical behavior and permeability characteristics. In order to study the mechanical properties and permeability characteristics of red sandstone under different temperature environments, a seepage test under high temperature and triaxial compression is carried out based on the RLW-2000 multi-field coupling tester. The results show that the plastic flow of red sandstone at the stress peak under the same temperature is more obvious with the increase of confining pressure. In addition, as the confining pressure gradient increases, the permeability decreases and the trend becomes slower. And the higher the operating temperature, the easier to produce seepage channels inside the rock sample. The development of fissures is rapidly developed under the effect of temperature, so the seepage channels are widened and increased, and the permeability is greatly increased. The constitutive model of rock statistical damage considering the interaction of high temperature and osmotic pressure was constructed based on the experimental data and combining theoretical methods to reveal the characteristics of permeability evolution induced by thermal damage of rocks. The research results can be used as a reference for monitoring rock stability during geological engineering projects involving thermal-seepage-stress coupling conditions.

scholarly journals Experimental Study on Rock-Like Specimens with Single Flaw under Hydro-Mechanical Coupling

2019 ◽  
Vol 9 (16) ◽  
pp. 3234 ◽  
Author(s):  
Jinquan Xing ◽  
Cheng Zhao ◽  
Songbo Yu ◽  
Hiroshi Matsuda ◽  
Chuangchuang Ma
Keyword(s):  
Mechanical Properties ◽  
Shear Failure ◽  
Water Pressure ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Tensile Failure ◽  
Compression Tests ◽  
Cracking Behavior ◽  
Mechanical Coupling ◽  
High Confining Pressure

In order to study the mechanical characteristics and cracking behavior of jointed rock mass under hydro-mechanical coupling, a series of uniaxial compression tests and triaxial compression tests were carried out on cylinder gypsum specimens with a single pre-existing flaw. Under different confining pressures, water pressure was injected on the pre-existing flaw surface through a water injection channel. The geometrical morphology and tensile or shear properties of the cracks were determined by X-ray computed tomography (CT) and scanning electron microscope (SEM). Based on the macro and micro observation, nine types of cracks that caused the specimen failure are summarized. The results of mechanical properties and crack behavior showed that the confining pressure inhibited the tensile cracks, and shear failure occurred under high confining pressure. The water pressure facilitated the initiation and extension of tensile crack, which made the specimens prone to tensile failure. However, under the condition of high confining pressure and low water pressure, the lubrication effect had a significant effect on the failure pattern, under which the specimens were prone to shear failure. This experimental research on mechanical properties and cracking behavior under hydro-mechanical coupling is expected to increase its fundamental understanding.

scholarly journals Mechanical properties and acoustic emission characteristics of granite under thermo-hydro-mechanical coupling

2021 ◽  
Vol 25 (6 Part B) ◽  
pp. 4585-4596
Author(s):  
Xin-Zhong Wang ◽  
Dong Wang ◽  
Zhe-Wei Wang ◽  
Xiao-Juan Yin ◽  
Xue-Jun Zhou ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Acoustic Emission ◽  
Elastic Modulus ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Thermal Cracking ◽  
Confining Pressure ◽  
Mechanical Coupling ◽  
Increasing Temperature

Exploring the mechanical properties and thermal cracking characteristics of rock under thermo-hydro-mechanical coupling in detail is of great importance for the safe excavation and stability of deep rock engineering. The mechanical properties and thermal cracking characteristics of granite under burial depths of 1000 m (confining pressure of 25 MPa) and 1600 m (confining pressure of 40 MPa) at a temperature of 110?C and a pore water pressure of 10 MPa were studied. The results show that the elastic modulus decreases with increasing temperature under a confining pressure of 25 MPa, whereas under a confining pressure of 40 MPa, the elastic modulus increases with increasing temperature. As the pore water pressure increases, the elastic modulus decreases slightly. Poisson?s ratio increas?es with increasing temperature below 40?C but decreases from 50-110?C. Pois?son?s ratio increases as pore water pressure increases. During the heating process, acoustic emission activity is first detected at 30-40?C and is relatively stable from 40-90?C. The acoustic emission activity increases sharply at 90-110?C, and the thermal cracking threshold of granite under thermo-hydro-mechanical coupling is approximately 95?C.

scholarly journals Earthquakes and extreme rainfall induce long term permeability enhancement of volcanic island hydrogeological systems

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
B. Vittecoq ◽  
J. Fortin ◽  
J. Maury ◽  
S. Violette
Keyword(s):  
Water Pressure ◽  
Extreme Rainfall ◽  
Threshold Value ◽  
Water Levels ◽  
Earth Tides ◽  
Permeability Evolution ◽  
Near Surface ◽  
Permeability Enhancement ◽  
Volcanic Islands ◽  
Permeability Increase

AbstractEarthquakes affect near-surface permeability, however temporal permeability evolution quantification is challenging due to the scarcity of observations data. Using thirteen years of groundwater level observations, we highlight clear permeability variations induced by earthquakes in an aquifer and overlaying aquitard. Dynamic stresses, above a threshold value PGV > 0.5 cm s−1, were mostly responsible for these variations. We develop a new model using earth tides responses of water levels between earthquakes. We demonstrate a clear permeability increase of the hydrogeological system, with the permeability of the aquifer increasing 20-fold and that of the aquitard 300-fold over 12 years, induced by fracture creation or fracture unclogging. In addition, we demonstrate unprecedented observations of increase in permeability due to the effect of extreme tropical deluges of rainfall and hurricanes. The water pressure increase induced by the exceptional rainfall events thus act as piston strokes strong enough to unclog congested fractures by colloids, particles or precipitates. Lastly, an analysis of regional permeabilities also highlights a permeability increase over geological timeframes (× 40 per million years), corroborating the trend observed over the last decade. This demonstrates that permeability of aquifers of andesitic volcanic islands, such as the Lesser Antilles, significantly evolve with time due to seismic activity and extreme rainfall.

Experiment Study of Rock Damage and Permeability Meso-Mechanical Coupling Failure Model under Complex Condition

2010 ◽  
Vol 40-41 ◽  
pp. 354-360
Author(s):  
Ji Kun Zhao
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Confining Pressure ◽  
Coupling Mechanism ◽  
Mechanism Analysis ◽  
Force Transmission ◽  
Mechanical Coupling ◽  
Compression Sample ◽  
Weak Part

Pore water pressure and the changes of crustal deformation, fault rupture and seismic activity has important influence. So the pore water pressure and load rock stress – hydro-mechanical coupling mechanism is very important. This paper mainly studies the rock specimens of hydraulic crack damage simulation. This study found: with the increase of the axial compression, sample is on the surface crack. Crack characteristics is smooth and continuously expanding. With the load increasing at the same time, the number of samples is also increased damage elements. The sample was through the cracks. This is due to the effect of water pressure to reduce the size of confining pressure .From the failure mechanism analysis, the distribution of stress non-uniform material will not uniformity, reflected in the actual rock because of the grain and the defects of the random distribution. When the load, the composition of force transmission effect of different deformation and stress in rock, the internal non-uniform stress concentration, local, it will directly cause the weak part, and micro cracks generated change the failure mode of materials.

scholarly journals Experimental Study on Seepage and Fracture Characteristics of Cemented Rock Samples under Triaxial Stress

Lithosphere ◽  
2021 ◽  
Vol 2021 (Special 7) ◽  
Author(s):  
Chong Li ◽  
Sifeng He
Keyword(s):  
Rock Sample ◽  
Water Pressure ◽  
Probability Model ◽  
Confining Pressure ◽  
Permeability Evolution ◽  
Volume Strain ◽  
Crack Network ◽  
Rock Samples ◽  
Crack Volume ◽  
Three Stages

Abstract To study the seepage and fracture characteristics of cemented rock strata, a series of triaxial seepage tests on cemented rock samples under different confining pressures and water pressures were carried out in this study. The triaxial strength, elastic modulus, volume strain, and the permeability of the cemented rock samples were analyzed by the seepage unit connection probability model and Kozeny-Carman model. Based on test results, the stress state of cemented rock samples was divided into four stages: nonlinear compaction stage, linear elastic stage, stress yield stage, and failure and postfailure stage. The triaxial strength of the cemented rock samples gradually increased with the increase of confining pressure but decreased with the increase of water pressure. The elastic modulus of the cemented rock sample increased with the increase of confining pressure but decreased with the increase of water pressure. Besides, the volume strain of the cemented rock sample was analyzed, and the volume strain change of the cemented rock sample was also classified into three stages: the increasing stage of crack volume strain, the stable stage of crack volume strain, and the decreasing stage of crack volume strain. Based on the results of triaxial seepage tests, the evolution of permeability was divided into the declining stage, increasing stage, and redescend stage. Through the seepage unit connection probability model and Kozeny-Carman model, the evolution of crack volume was obtained, and the evolution of crack volume with axial strain was also classified into three stages: the original pore closure stage, crack network expansion stage, and crack network closure stage. The permeability evolution and the crack volume evolution were also compared. The comparison results suggest that three stages of crack volume evolution are all ahead of three stages of permeability evolution, verifying that the crack propagation induces the formation of seepage channels in cemented rock samples. This research will provide a valuable reference for the study of instability and water inrush mechanism in cemented rock strata.

Quality analysis and prospects for use of lupin seeds of Belarusian selection

2020 ◽  
Vol 3 (1) ◽  
pp. 22
Author(s):  
Lyudmila Rukshan ◽  
Alena Navazhilova ◽  
Dmitry Kudin
Keyword(s):  
Chemical Composition ◽  
Physical Properties ◽  
Wheat Flour ◽  
Great Influence ◽  
Quality Analysis ◽  
Bakery Products ◽  
Whole Grain ◽  
Technological Parameters ◽  
Protein Food ◽  
Lupin Seeds

The paper investigates technological parameters of the quality of low-alkaloid lupin of five cultivars selected and grown in the Republic of Belarus during the years from 2007 to 2017. Prospects for the use of the obtained seeds have been studied. This study reveals great influence of cultivar and climatic conditions during growth of lupin seeds on correlation of anatomic parts in seeds as well as on their physical properties. Cultivar of lupin seeds Jan is recommended for whole grain flour and graded flour production based on its anatomic composition, uniformity and physical properties. A comparative analysis of chemical composition, quality parameters and technological properties of lupin flour has been done. The chemical composition of lupin flour, of whole grain lupin flour, in particular, has been found to be relatively low in starch, high in protein, food fibers, minerals and organic acids. As a result, whole grain lupin flour has been proved to have higher food value when compared to traditional wheat flour. This paper demonstrates the difference between lupin flour characteristics and those of wheat flour in terms of color, acidity, enzymatic activity and adsorbing properties. This study reveals the possibility of use of lupin flour in bakery products by substituting traditional types of flour with lupin flour at 10-30% levels, as well as by replacing egg products with lupin flour at 25-50% levels. The work highlights the use of lupin flour at the stages of dough kneading, dough preparation, foam and emulsion production mainly by using rapid dough making methods.Practical applicationsRecommendations have been made on the usage of lupin flour in the technological process of bakery products manufacturing, macaroni and flour confectionery products production.

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