scholarly journals Characterization and Modeling Study on Softening and Seepage Behavior of Weakly Cemented Sandy Mudstone after Water Injection

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Junting Guo ◽  
Teng Teng ◽  
Xiaoyan Zhu ◽  
Yuming Wang ◽  
Zhaolong Li ◽  
...  
Keyword(s):  
Water Saturation ◽  
Water Injection ◽  
Experimental Studies ◽  
Friction Angle ◽  
Engineering Practice ◽  
Permeability Evolution ◽  
Exponential Relationship ◽  
Softening Effect ◽  
Negative Exponential ◽  
Sandy Mudstone

Water injection-induced rock softening and the associated water seepage characteristics are the common and basic problems in underground reservoir construction and the prevention of mine water disaster. In this paper, a series of experimental studies was carried out to investigate these characteristics with the weakly cemented sandy mudstone collected from Shendong Buertai coal mine, China. The characteristics of water softening and the stress-seepage interactions in water-saturated weakly cemented sandy mudstone were directly obtained. Then, a modification method of the constitutive model for rock mass considering the softening effect and a stress-damage-driven model for permeability evolution were established. Research results show that water saturation reduces the tensile strength, compressive strength, and cohesion by 56% and reduces the elastic modulus by 28%. The hydraulic effects on Poisson’s ratio and internal friction angle are negligible. The relationship between the permeability of weakly cemented sandy mudstone with complete compaction deformation is to be divided into three stages of seepage shielding, seepage surge, and seepage recovery. Rock permeability in each stage has a negative exponential relationship with the effective stress. This research provides a theoretical basis for the researches of hydromechanical couplings on weakly cemented sandy mudstone, which is insightful for rock engineering practice.

scholarly journals Characterization and Modeling Study on Softening and Seepage Behavior of Weakly Cemented Sandy Mudstone After Water Injection

2021 ◽  
Author(s):  
Junting Guo ◽  
Teng Teng ◽  
Xiaoyan Zhu ◽  
Yuming Wang ◽  
Zhaolong Li
Keyword(s):  
Water Saturation ◽  
Water Injection ◽  
Friction Angle ◽  
Engineering Practice ◽  
Permeability Evolution ◽  
Exponential Relationship ◽  
Softening Effect ◽  
Hard Roof ◽  
Negative Exponential ◽  
Sandy Mudstone

Abstract Water injection induced rock softening and the associated water seepage characteristics are the common and basic problems in hard roof pressure relief, underground reservoir construction and the prevention of mine water disaster. In this paper, a series of laboratory studies was carried out to investigate these characteristics with the weakly cemented sandy mudstone collected from Shendong Buertai coal mine, China. The characteristics of water softening and the stress-seepage interactions in saturated weekly cemented sandy mudstone were directly obtained. Then a modification method of the constitutive model for rock mass considering the softening effect and a stress-damage-driven model for permeability evolution were established. Research results show that water saturation reduces the tensile strength, compressive strength and cohesion by 56%, and reduces the elastic modulus by 28%. The hydraulic effect on Poisson’s ratio and internal friction angle is negligible. The relationship between the permeability of weakly cemented sandy mudstone with complete compaction deformation is to be divided into three stages of seepage shielding, seepage surge and seepage recovery. Rock permeability in each stage has a negative exponential relationship with the effective stress. This research provides a theoretical basis for the researches of hydro-mechanical couplings on weakly cemented sandy mudstone, which is insightful for rock engineering practice.

Re-saturation targets identified from 4D seismic softening responses in the Forties Field

2017 ◽  
Vol 8 (1) ◽  
pp. 473-483 ◽  
Author(s):  
Lyndsay Singer ◽  
Grant Byerley ◽  
Phil Rose
Keyword(s):  
Water Saturation ◽  
Water Injection ◽  
Hydrodynamic Interactions ◽  
Driving Mechanism ◽  
Pressure Measurements ◽  
Softening Effect ◽  
Average Water ◽  
Acoustic Softening ◽  
4D Seismic ◽  
Over Time

AbstractA novel 4D methodology by targeting softening responses, a decrease in impedance over time, is described from the Forties Field. It is demonstrated that these anomalies identified areas where oil had re-saturated previously swept rock. When first observed in some of the older vintages of 4D data, softening responses were dismissed as side lobes of underlying water-swept reservoirs. With improved 4D data quality, softening responses were seen to be clearly responding to an acoustic softening effect isolated in the reservoir. Pressure measurements ruled out hypotheses of gas exsolution or geomechanically induced dilatation of the overlying shale.At the time of writing 22 re-saturation targets had been drilled at Forties with an average water saturation (Sw) of 28%, close to virgin conditions. These results indicated that a previously swept sand can be re-saturated to near initial oil conditions.The driving mechanism behind the re-saturation is understood to be related to changes in both production offtake and water injection. The resulting complex hydrodynamic interactions appeared to be moving banks of oil around the field. From 2011 to year-end of 2015 re-saturation targets produced 14.6 MMBO and were a key target type at the Forties Field.

Model for predicting tensile strength of unsaturated cohesionless soils

2018 ◽  
Vol 55 (9) ◽  
pp. 1313-1333 ◽  
Author(s):  
Penghai Yin ◽  
Sai K. Vanapalli
Keyword(s):  
Tensile Strength ◽  
Characteristic Curve ◽  
Experimental Studies ◽  
Friction Angle ◽  
Matric Suction ◽  
Degree Of Saturation ◽  
Engineering Practice ◽  
Cohesionless Soils ◽  
Proposed Model ◽  
Earth Structures

The influence of tensile strength on the behaviour of cohesionless soils is typically ignored in geotechnical engineering practice. However, the tensile cracking and subsequent failure characteristics of earth structures, such as dams, slopes and embankments, are significantly influenced by the tensile strength. For this reason, a semi-empirical model is proposed for predicting the variation of the tensile strength of unsaturated cohesionless soils with the degree of saturation, using the soil-water characteristic curve (SWCC) as a tool. The proposed model is capable of predicting the tensile strength arising from matric suction and surface tension, which are related to saturated pores and to the air–water interface associated with water bridges around interparticle contacts in unsaturated pores, respectively. Information about (i) the matric suction (ua– uw), the capillary degree of saturation (Sc), and the residual degree of saturation (Sr) derived from the SWCC; (ii) the mean particle size (d50) and the coefficient of uniformity (Cu) from the grain-size distribution curve; (iii) the void ratio (e); and (iv) the friction angle ([Formula: see text]) at low normal stress level is required to employ this model. The proposed model is validated by comparing the prediction results with measured tensile strength of 10 different unsaturated cohesionless soils (including five sandy soils and five silty soils). The proposed model is promising for use in engineering practice applications as it only requires conventional soil properties, alleviating the need for cumbersome experimental studies for the determination of tensile strength of unsaturated cohesionless soils.

scholarly journals Numerical Simulation and Engineering Application of Coalbed Water Injection

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Yijie Shi ◽  
Pengfei Wang ◽  
Ronghua Liu ◽  
Xuanhao Tan ◽  
Wen Zhang
Keyword(s):  
Numerical Simulation ◽  
Process Parameters ◽  
Water Injection ◽  
Engineering Application ◽  
Working Environment ◽  
Engineering Practice ◽  
Characteristic Parameters ◽  
Injection Process ◽  
Working Face ◽  
Dust Reduction

Coalbed water injection is the most basic and effective dust-proof technology in the coal mining face. To understand the influence of coalbed water injection process parameters and coalbed characteristic parameters on coal wetting radius, this paper uses Fluent computational fluid dynamics software to systematically study the seepage process of coalbed water injection under different process parameters and coalbed characteristic parameters, calculation results of which are applied to engineering practice. The results show that the numerical simulation can help to predict the wetness range of coalbed water injection, and the results can provide guidance for the onsite design of coalbed water injection process parameters. The effect of dust reduction applied to onsite coalbed water injection is significant, with the average dust reduction rates during coal cutting and support moving being 67.85% and 46.07%, respectively, which effectively reduces the dust concentration on the working face and improves the working environment.

scholarly journals Ice nucleation efficiency of AgI: review and new insights

2016 ◽  
Author(s):  
Claudia Marcolli ◽  
Baban Nagare ◽  
André Welti ◽  
Ulrike Lohmann
Keyword(s):  
Water Saturation ◽  
Experimental Studies ◽  
Freezing Temperature ◽  
Nucleating Agent ◽  
Companion Paper ◽  
Chem Phys ◽  
Ice Nucleation ◽  
Lattice Match ◽  
Ice Nuclei ◽  
Immersion Freezing

Abstract. AgI is one of the best investigated ice nuclei. It has relevance for the atmosphere since it is used for glaciogenic cloud seeding. Theoretical and experimental studies over the last sixty years provide a complex picture of silver iodide as ice nucleating agent with conflicting and inconsistent results. This review compares experimental ice nucleation studies in order to analyse the factors that influence the ice nucleation ability of AgI. We have performed experiments to compare contact and immersion freezing by AgI. This is one of three papers that describe and analyse contact and immersion freezing experiments with AgI. In Nagare et al. (Nagare, B., Marcolli, C., Stetzer, O., and Lohmann, U.: Comparison of measured and calculated collision efficiencies at low temperatures, Atmos. Chem. Phys., 15, 13759–13776, doi:10.5194/acp-15-13759-2015, 2015) collision efficiencies based on contact freezing experiments with AgI are determined and compared with theoretical formulations. In a companion paper, contact freezing experiments are compared with immersion freezing experiments conducted with AgI, kaolinite, and ATD as ice nuclei. The following picture emerges from this analysis: The ice nucleation ability of AgI seems to be enhanced when the AgI particle is on the surface of a droplet, which is indeed the position that a particle takes when it can freely move in a droplet. Ice nucleation by particles with surfaces exposed to air, depends on water adsorption. AgI surfaces seem to be most efficient as ice nuclei when they are exposed to relative humidity at or even above water saturation. For AgI particles that are totally immersed in water, the freezing temperature increases with increasing AgI surface area. Higher threshold freezing temperature seem to correlate with improved lattice matches as can be seen for AgI-AgCl solid solutions and 3AgI•NH4I•6H2O, which have slightly better lattice matches with ice than AgI and also higher threshold freezing temperatures. However, the effect of a good lattice match is annihilated when the surfaces have charges. Also, the ice nucleation ability seems to decrease during dissolution of AgI particles. This introduces an additional history and time dependence of ice nucleation in cloud chambers with short residence times.

scholarly journals Water Softening Mechanism and Strength Model for Saturated Carbonaceous Mudstone in Panzhihua Airport, China

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Ziwen Wang ◽  
Jifang Du ◽  
Shuaifeng Wu ◽  
Yingqi Wei ◽  
Jianzhang Xiao ◽  
...  
Keyword(s):  
Shear Strength ◽  
Water Saturation ◽  
Structural Characteristics ◽  
Water Immersion ◽  
Analytical Techniques ◽  
Friction Angle ◽  
Mechanical Tests ◽  
Water Softening ◽  
Softening Mechanism ◽  
The Stability

To identify the water softening mechanisms that caused landslides in Panzhihua Airport, China, property and saturation tests of the mudstones extracted from a representative landslide were proposed. In this paper, water saturation tests were carried out on samples of carbonaceous mudstone collected from the east side of the No. 12 landslide at the airport. A number of different analytical techniques and mechanical tests were used to determine changes in chemical composition, mineral assemblages, and mudstone structural characteristics, including shear strength, after the mudstone had been softened. Three kinds of changes caused by water and three mudstone softening stages are proposed. The results show that the water has a significant influence on the properties of the mudstone, so the stability of the mudstone in the watery period is a big threat to the upper structure. A model for water immersion mudstone strength softening is developed. The model incorporates a permeability coefficient, the hydraulic gradient, and time; the model can be used to determine the mudstone’s shear strength and internal friction angle. This study provides a reference for the study of rock softened by water immersion.

scholarly journals Determination of Equivalent Mohr-Coulomb Criterion from Generalised Hoek-Brown Criterion

2021 ◽  
Author(s):  
Qingqing Yang ◽  
Fei Cai
Keyword(s):  
Principal Stress ◽  
Least Squares Method ◽  
Method Comparison ◽  
Friction Angle ◽  
Engineering Practice ◽  
Shear Strength Parameters ◽  
Strength Parameters ◽  
Coulomb Criterion ◽  
Minor Principal Stress

Abstract A new analytical solution is presented for determining equivalent Mohr-Coulomb (MC) shear strength parameters over an arbitrary interval of minor principal stress σ3 from the generalised Hoek-Brown (HB) criterion using least squares method. Comparison with several published examples demonstrates that the proposed solution had a capacity to accurately determine equivalent MC parameters over a given interval of σ3, as well as instantaneous MC parameters by using a very small interval of σ3. EMC parameters depended heavily on the interval of σ3, which highlighted the importance of intervals of σ3. A calculation case shows that the equivalent internal friction angle and cohesion over the interval of σ3 from tension cut-off σcut−off to maximum minor principal stress σ3max were approximately 12% smaller and 10.3% larger than those over an interval from tensile strength to σ3max, respectively. The proposed solution offers great flexibility for the application of the HB criterion with existing methods based on the MC criterion for rock engineering practice.

Basics of Metals Theory of Extraction by Means of Chemical Water Solutions Filtration through Underground Ores

2014 ◽  
Vol 1020 ◽  
pp. 472-477 ◽  
Author(s):  
Vruyr Sargsyan ◽  
Emil Saratikyan
Keyword(s):  
Molecular Diffusion ◽  
Water Saturation ◽  
Water Injection ◽  
Mining Industry ◽  
Extraction Methods ◽  
Ore Deposits ◽  
Metal Salts ◽  
Chemical Reagents ◽  
Ore Body ◽  
Waste Dumps

Abstract. Geo-technological extraction methods recently are widely used in the mining industry. Removing the metals from underground ore deposits is carried out by injecting chemicals (solvents, oxidants, reducing agents) into wells drilled in them, and the subsequent extraction of metals from saturated solutions. Particularly, this method utilized for the extraction of uranium from flooded sediments and copper from poor (substandard) ores, as well as some non-ferrous and rare metals from waste dumps and tailings of substandard ore mines and processing enterprises. The paper discusses methods developed for prediction of moisture content (water saturation) in rocks under filtration of liquid with incomplete saturation of pores while changing the concentration of the metal in the liquid phase (in an ore body), as well as problems of dissolution and desorption of metal salts on the surface cracks or pores on ore body based on molecular diffusion equation of metal salts. The present work conducted for developing the methods for calculating the liquid filtration through underground deposits of minerals and forecasting of dissolving and washing out metals. It is shown that the processes which take place with the use of chemical reagents are different comparing to the similar processes with water injection. These data allow to predict the changes in the concentration of salts and metals in the liquid and solid phases depending on time.

scholarly journals Shale volume and permeability of the Miocene unconsolidated turbidite sands of Bonga oil field, Niger delta, Nigeria

2017 ◽  
Vol 5 (1) ◽  
pp. 37 ◽  
Author(s):  
Inyang Namdie ◽  
Idara Akpabio ◽  
Agbasi Okechukwu .E.
Keyword(s):  
Niger Delta ◽  
Gamma Ray ◽  
Water Saturation ◽  
Strong Dependence ◽  
Water Injection ◽  
Oil Field ◽  
Reservoir Properties ◽  
Injection Wells ◽  
Log Data ◽  
Shale Volume

Bonga oil field is located 120km (75mi) southeast of the Niger Delta, Nigeria. It is a subsea type development located about 3500ft water depth and has produced over 330 mmstb of hydrocarbon till date with over 16 oil producing and water injection wells. The producing formation is the Middle to Late Miocene unconsolidated turbidite sandstones with lateral and vertical homogeneities in reservoir properties. This work, analysis the petrophysical properties of the reservoir units for the purpose of modeling the effect of shale content on permeability in the reservoir. Turbidite sandstones are identified by gamma-ray log signatures as intervals with 26-50 API, while sonic, neutron, resistivity, caliper and other log data are applied to estimate volume of shale ranging between 0.972 v/v for shale intervals and 0.0549 v/v for turbidite sands, water saturation of 0.34 v/v average in most sand intervals, porosity range from 0.010 for shale intervals to 0.49 v/v for clean sands and permeability values for the send interval 11.46 to2634mD, for intervals between 7100 to 9100 ft., Data were analyzed using the Interactive Petrophysical software that splits the whole curve into sand and shale zones and estimates among other petrophysical parameters the shale contents of the prospective zones. While Seismic data revealed reservoir thickness ranging from 25ft to over 140ft well log data within the five wells have identified sands of similar thickness and estimated average permeability of700mD. Within the sand units across the five wells, cross plots of estimated porosity, volume of shale and permeability values reveal strong dependence of permeability on shale volume and a general decrease in permeability in intervals with shale volume. It is concluded that sand units with high shale contents that are from0.500 to0.900v/v will not provide good quality reservoir in the field.

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