Triaxial Testing of Gas Shale Permeability Dependence on Heterogeneous Stress With Respect to Bedding

2019 ◽  
Author(s):  
Yufei Chen ◽  
Changbao Jiang ◽  
Guangzhi Yin ◽  
Andrew K. Wojtanowicz ◽  
Dongming Zhang
Keyword(s):  
Normal Stress ◽  
Tangential Stress ◽  
Shale Gas ◽  
Gas Flow ◽  
Triaxial Testing ◽  
Permeability Change ◽  
Tangential Stresses ◽  
Longmaxi Shale ◽  
Shale Permeability

Abstract Shale gas has recently become the most promising source of unconventional hydrocarbon energy. Shale gas well deliverability and economics depend on extremely low permeability that is not only dependent on the rock bedding trend but is also controlled by in-situ stresses. Thus, prediction of well’s deliverability requires understanding permeability of a dipping shale with natural bedding under conditions of unequal stresses in-situ. The purpose of this study was to determine relative contributions of normal and tangential stresses with respect to the rock bedding plane on permeability evolution of Longmaxi shale in the Sichuan Basin, southwest China. The study involved an analysis of the rock bedding structure, followed with triaxial testing of rock samples and theoretical modeling. We used SEM observation to identify existence of microfractures and numerous inter-particle pores along the shale bedding planes that provide dominant pathways for gas flow depending upon closing stress value. Stress-dependent permeability was tested with a newly-developed multi-functional true triaxial geophysical (TTG) apparatus providing for a steady state gas flow through the rock sample under conditions of normal stress and two unequal tangential stresses. Also simulated were the effects of stress-bedding and load cycling. The results showed shale permeability reduction during the stress loading process and its gradual recovery during the unloading process for both normal and tangential stress loading cycles. A hysteresis of the permeability response to cyclic loading was the largest when normal stress cycling was dominant. Moreover, permeability change was more pronounced in response to normal stress but some effects of the tangential stresses were also observed — particularly when the tangential stresses were dominant. A theoretical model was derived to describe permeability change with effective stress in the presence of normal and tangential stresses. The model was empirically matched with the experimental results. Assessment of relative contributions of normal and tangential stresses was quantified with the analysis of variance (ANOVA). The analysis revealed significance levels of normal stress, and two tangential stresses σt1 and σt2 on shale permeability as 81%, 5% and 14%, respectively, showing dominant effect of normal stress with clear contribution of tangential stresses. An almost 20-percent contribution of tangential stress loading to permeability response indicates a need for improvement in computing effective stress in permeability predictions of the Longmaxi shale. It also warrants testing other gas shales to specifically determine the effect.

Permeability and Effective Stress in Dipping Gas Shale Formation With Bedding—Experimental Study

2020 ◽  
Vol 142 (10) ◽  
Author(s):  
Yufei Chen ◽  
Changbao Jiang ◽  
Guangzhi Yin ◽  
Andrew K. Wojtanowicz ◽  
Dongming Zhang
Keyword(s):  
Normal Stress ◽  
Effective Stress ◽  
Bedding Plane ◽  
Permeability Change ◽  
Permeability Evolution ◽  
Tangential Stresses ◽  
Significance Levels ◽  
Percent Contribution ◽  
Shale Formation ◽  
Shale Permeability

Abstract Shale gas well deliverability and economics depend on extremely low permeability that is not only dependent on the rock bedding trend but also controlled by in situ stresses. The purpose of this study was to determine relative contributions of normal and tangential stresses with respect to the rock bedding plane on permeability evolution of shale. The study involved an analysis of the rock bedding structure, followed by triaxial testing of rock samples and theoretical modeling. Also simulated were the effects of stress-bedding and load cycling. The results showed shale permeability reduction during the stress loading process and its gradual recovery during the unloading process. Permeability change was more pronounced in response to normal stress but some effects of the tangential stresses were also observed. Moreover, a theoretical model was derived to describe permeability change with effective stress in the presence of normal and tangential stresses. The model was empirically matched with the experimental results. The assessment of relative contributions of normal and tangential stresses was quantified with the analysis of variance (ANOVA). The analysis revealed significance levels of normal stress, and two tangential stresses σt1 and σt2 on shale permeability as 81%, 5%, and 14%, respectively. An almost 20-percent contribution of tangential stress loading to permeability response indicates a need for the improvement in computing effective stress. Therefore, a new method was suggested to determine effective stress when predicting permeability evolution of shale.

In Situ Sequestration of a Hydraulic Fracturing Fluid in Longmaxi Shale Gas Formation in the Sichuan Basin

2019 ◽  
Vol 33 (8) ◽  
pp. 6983-6994 ◽  
Author(s):  
Bin Yang ◽  
Hao Zhang ◽  
Yili Kang ◽  
Lijun You ◽  
Jiping She ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Shale Gas ◽  
Sichuan Basin ◽  
Fracturing Fluid ◽  
Gas Formation ◽  
Longmaxi Shale ◽  
The Sichuan Basin ◽  
Hydraulic Fracturing Fluid

scholarly journals Reservoir diffusion properties of the Longmaxi shale in Shizhu area, Southern Sichuan basin, China

2018 ◽  
Vol 36 (5) ◽  
pp. 1086-1102 ◽  
Author(s):  
Si Chen ◽  
Shangbin Chen ◽  
Uwamahoro Clementine ◽  
Yu Liu ◽  
Chu Zhang
Keyword(s):  
Diffusion Coefficient ◽  
Shale Gas ◽  
Gas Flow ◽  
Confining Pressure ◽  
Seepage Flow ◽  
Important Indicator ◽  
Longmaxi Formation ◽  
Average Value ◽  
Concentration Method ◽  
Longmaxi Shale

Diffusion ability is an important indicator of shale gas reservoir quality. In this paper, the diffusion coefficient of the Longmaxi Formation is measured via the free hydrocarbon concentration method, and the diffusion ability, influencing factors, and seepage flow are discussed. Results show that the diffusion coefficient of the Longmaxi Formation is between 1.23 × 10−5 and 2.98 × 10−5 cm2 s−1 with an average value of 2.19 × 10−5 cm2 s−1 (confining pressure 3.0 MPa). The diffusion coefficient is calculated for various pressures using an empirical formula ( D = 0.339 K0.67/ M0.5) and experimentally measured data. The estimated, temperature-corrected diffusion coefficient of the Longmaxi Formation is 3.94 × 10−6–7.24 × 10−6 cm2 s−1 with an average value of 5.28 × 10−6 cm2 s−1 for depths from 1000 to 3000 m (confining pressure 16.7–39.7 MPa). The diffusion coefficient increases with increasing depth of the reservoir due to the changes in pressure and temperature. Fitting parameters show that the porosity of the reservoir and clay minerals is positively correlated with the diffusion coefficient, and the diffusion coefficient is also related to factors such as total organic carbon and the maximum reflectance of vitrinite ( Ro). The diffusion flow rate is 0.177–0.204 m3 d−1 with an average of 0.182 m3 d−1. Linear seepage flow is 4.95 × 10−4–14.29 × 10−4 m3 d−1 with an average of 8.87 × 10−4 m3 d−1, calculated from the diffusion coefficient and permeability per unit flow. These results indicate that the migration of shale gas in the deep region of the reservoir is mainly by diffusion. Therefore, diffusion is an important shale gas flow mechanism.

Research on Numerical Simulation of Gas Flow in Shale Matrix Micro Pore

2018 ◽  
Vol 783 ◽  
pp. 73-78
Author(s):  
Zong Xiong Cao ◽  
Xing Guo Yu ◽  
Kui Xiang
Keyword(s):  
Porous Medium ◽  
Shale Gas ◽  
Gas Flow ◽  
Scheme Design ◽  
Matrix Permeability ◽  
Longmaxi Shale ◽  
Digital Core ◽  
Micro Flow ◽  
Imagej Software ◽  
Boltzmann Method

In view of Longmaxi shale core in Sichuan basin, two-dimensional images of shale core were given by using scanning electron microscopy (SEM), and processed by ImageJ software to reconstruct the 3D shale matrix digital core, the digital core can reflect the nano pore structure more accurately. LBM model of gas flow in shale porous medium is established based on lattice Boltzmann method. The corresponding boundary conditions were established based on slip phenomenon for shale gas in porous medium micro flow, which can simulate gas flow in the micro pore in shale more realistic. The numerical results show that the microscale effect becomes obvious with the increase of Knudsen number, and the more obvious the non-Darcy phenomenon of gas flow in the shale matrix. The research results of this paper provide a theoretical basis for shale matrix permeability calculation, shale gas well productivity evaluation and development scheme design.

scholarly journals Review of Formation and Gas Characteristics in Shale Gas Reservoirs

Energies ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 5427
Author(s):  
Boning Zhang ◽  
Baochao Shan ◽  
Yulong Zhao ◽  
Liehui Zhang
Keyword(s):  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Shale Gas ◽  
Physical Parameters ◽  
Gas Reservoirs ◽  
Shale Formations ◽  
Adsorbed Gas ◽  
Shale Gas Reservoirs ◽  
Longmaxi Shale

An accurate understanding of formation and gas properties is crucial to the efficient development of shale gas resources. As one kind of unconventional energy, shale gas shows significant differences from conventional energy ones in terms of gas accumulation processes, pore structure characteristics, gas storage forms, physical parameters, and reservoir production modes. Traditional experimental techniques could not satisfy the need to capture the microscopic characteristics of pores and throats in shale plays. In this review, the uniqueness of shale gas reservoirs is elaborated from the perspective of: (1) geological and pore structural characteristics, (2) adsorption/desorption laws, and (3) differences in properties between the adsorbed gas and free gas. As to the first aspect, the mineral composition and organic geochemical characteristics of shale samples from the Longmaxi Formation, Sichuan Basin, China were measured and analyzed based on the experimental results. Principles of different methods to test pore size distribution in shale formations are introduced, after which the results of pore size distribution of samples from the Longmaxi shale are given. Based on the geological understanding of shale formations, three different types of shale gas and respective modeling methods are reviewed. Afterwards, the conventional adsorption models, Gibbs excess adsorption behaviors, and supercritical adsorption characteristics, as well as their applicability to engineering problems, are introduced. Finally, six methods of calculating virtual saturated vapor pressure, seven methods of giving adsorbed gas density, and 12 methods of calculating gas viscosity in different pressure and temperature conditions are collected and compared, with the recommended methods given after a comparison.

NbC and VC Nanoparticles Reinforced Fe-Si-Mn Matrix Composite In Situ Synthesized by Plasma Jet

2011 ◽  
Vol 415-417 ◽  
pp. 71-75
Author(s):  
Chun Xiang Cui ◽  
Yan Chun Li ◽  
Tie Bao Wang ◽  
Shuang Jin Liu ◽  
Suek Bong Kang
Keyword(s):  
Matrix Composite ◽  
Hybrid Composite ◽  
Gas Flow ◽  
Plasma Jet ◽  
Homogeneous Distribution ◽  
Active Nitrogen ◽  
Ceramic Particles ◽  
Nanometer Range ◽  
Short Time

In situ NbC and VC nanoparticles reinforced Fe-Si-Mn-Nb-V matrix composite was carried out using a plasma jet with a plasma gas flow of (Ar + CH4) for very short time. The process involve improving the efficiency of the reaction in terms of consumption of the available active nitrogen atoms as well as the production of very fine and homogeneous distribution of all reinforcing phases of ceramic particles, preferable in the nanometer range. The nanoreinforcements synthesized by in situ reaction in this hybrid composite are NbC and VC ceramic particles.

Lower limits of evaluation parameters for the lower Paleozoic Longmaxi shale gas in southern Sichuan Province

2013 ◽  
Vol 56 (5) ◽  
pp. 710-717 ◽  
Author(s):  
YanJun Li ◽  
Huan Liu ◽  
LieHui Zhang ◽  
ZongGang Lu ◽  
QiRong Li ◽  
...  
Keyword(s):  
Shale Gas ◽  
Sichuan Province ◽  
Lower Paleozoic ◽  
Longmaxi Shale ◽  
Lower Limits ◽  
Evaluation Parameters

Numerical Simulation of the Impact between the Front-End-Coated Projectile and the Substrate Coated by Ceramic Film

2012 ◽  
Vol 226-228 ◽  
pp. 2198-2202
Author(s):  
Zhi Lin Wu ◽  
Xiao Mei Wang
Keyword(s):  
Normal Stress ◽  
Tangential Stress ◽  
Stress Wave ◽  
Acoustic Impedance ◽  
Axial Direction ◽  
Interfacial Stress ◽  
Ceramic Film ◽  
Front End ◽  
Ceramic Films ◽  
The Impact

The propagation of the stress wave in axial direction during the impact between the front-end-coated projectile and the substrate coated by ceramic films is described by the stress wave theorem. The impact process is numerically simulated by ANSYS/LS-DYNA, where the shell unit is used for precision. The effects of thickness of the front-end coating on the interfacial stress are discussed in detail. Dependence of different ceramic films are also considered. Simulation results show that interfacial normal stress is much greater than tangential stress. The interfacial normal stress is greatest when the thickness of the projectile coating is 0.2 mm. The interfacial tangential stress increases slightly as the thickness of coating increases. Similar stress history in the interface occurs when the acoustic impedance of the films are close. Greater acoustic impedance results in smaller stress.

scholarly journals In-situ diffraction experiments at the Photon Factory MX beamlines

2014 ◽  
Vol 70 (a1) ◽  
pp. C500-C500
Author(s):  
Yusuke Yamada ◽  
Naohiro Matsugaki ◽  
Masahiko Hiraki ◽  
Ryuichi Kato ◽  
Toshiya Senda
Keyword(s):  
Gas Flow ◽  
Active Area ◽  
Array Detector ◽  
Data Sets ◽  
Diffraction Experiment ◽  
X Ray ◽  
Photon Factory ◽  
Large Active Area ◽  
In Situ Diffraction

Crystallization trial is one of the most important but time-consuming steps in macromolecular crystallography. Once a crystal appears in a certain crystallization condition, the crystal is typically harvested from the crystallization drop, soaked into a cryoprotection buffer, flash-cooled with a liquid nitrogen or cold gas flow and finally evaluated its diffraction quality by an X-ray beam. During these long process, crystal may be damaged and the result from the diffraction experiment does not necessarily reflect a nature of the crystal. On in-situ diffraction experiment, where a crystal in a crystallization drop is directly irradiated to an X-ray beam, a diffraction image from a crystal without any external factors such as harvesting and cryoprotection and, as a result, a nature of crystal can be evaluated quickly. In the Photon Factory, a new table-top diffractometer for in-situ diffraction experiments has been developed. It consists of XYZ translation stages with a plate handler, on-axis viewing system with a large numeric aperture and a plate rack where ten crystallization plates can be placed. These components sit on a common plate and it is placed on the existing diffractometer table in the beamline endstation. The CCD detector with a large active area and a pixel array detector with a small active area are used for acquiring diffraction images from crystals. Dedicated control software and user interface were also developed. Since 2014, user operation of the new diffractometer was started and in-situ diffraction experiments were mainly performed for evaluations of crystallization plates from a large crystallization screening project in our facility. BL-17A [1], one of micro-focus beamlines at the Photon Factory, is planned to be upgraded in March 2015. With this upgrade, a new diffractometer, which has a capability to handle a crystallization plate, will be installed so that diffraction data sets from crystals in crystallization drop can be collected.

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