Implication of Water-Rock Interaction for Enhancing Shale Gas Production

Horizontal well drilling and multi-stage hydraulic fracturing technologies are at the root of commercial shale gas development and exploitation.During these processes,typically,a large amount of working fluid enters the formation,resulting in widespread water-rock interaction.Deeply understanding such effects is required to optimize the production system.In this study,the mechanisms of water-rock interaction and the associated responses of shale fabric are systematically reviewed for working fluids such as neutral fluids,acid fluids,alkali fluids and oxidative fluids.It is shown that shale is generally rich in water-sensitive components such as clay minerals,acidsensitive components(like carbonate minerals),alkali-sensitive components(like quartz),oxidative-sensitive components(like organic matter and pyrite),which easily lead to change of rock fabric and mechanical properties owing to water-rock interaction.According to the results,oxidizing acid fluids and oxidizing fracturing fluids should be used to enhance shale gas recovery.This study also indicates that an aspect playing an important role in increasing cumulative gas production is the optimization of the maximum shut-in time based on the change point of the wellhead pressure drop rate.Another important influential factor to be considered is the control of the wellhead pressure considering the stress sensitivity and creep characteristics of the fracture network.

FLOCKING OF A THERMODYNAMIC CUCKER-SMALE MODEL WITH LOCAL VELOCITY INTERACTIONS

In this paper, we study the flocking behavior of a thermodynamic Cucker–Smale model with local velocity interactions. Using the spectral gap of a connected stochastic matrix, together with an elaborate estimate on perturbations of a linearized system, we provide a sufficient framework in terms of initial data and model parameters to guarantee flocking. Moreover, it is shown that the system achieves a consensus at an exponential rate.

Effect of the sloping seabed on 3D soil-spudcan interaction using a material point-finite element(MPM-FEM)model

The sloping seabed affects the bearing capacity and failure mechanism of soil,which may compromise the stability and safety of offshore structures such as jack-up platforms.This paper employs a coupled model combining the material point method and finite element method(MPM-FEM)to analyze the impact of sloping seabeds on the three-dimensional soil-spudcan interaction.The MPM-FEM model implements the B¯approach to solve the challenge of volumetric locking due to the incompressibility constraints imposed by yield criterion.It is validated against the centrifuge results.The effects of sloping seabeds on penetration resistance,soil flow pattern,lateral response,stress distribution,and failure mechanism are discussed.The soil mainly undergoes overall failure when the ratio of penetration depth to spudcan diameter(i.e.D P/D)is between 0 and 0.25.As the slope angle increases,the soil on the side of lower slope is expelled further,resulting in an asymmetric stress distribution and a larger horizontal sliding force of soil.When D P/D increases to 0.75,the soil transitions to localized plastic flow failure,and the range of soil flow affected by the spudcan penetration decreases.The results show that,when the slope angle increases,the lateral displacement and stress distribution on the lower slope of a sloping seabed is significantly larger than that of a horizontal seabed,impacting the spudcan and surrounding soil behavior.The study suggests that the seabed slope significantly affects the range of soil flow and failure at shallow penetration,indicating that the slope angle should be taken into account in the design and installation of offshore jack-up rigs,particularly in areas with sloping seabeds.

Multi-Body Dynamics Modeling of Heavy Goods Vehicle-Rail Interaction

Based on the principle of vehicle-track coupling dynamics, SIMPACK multi-body dynamics software is used to establish a C80 wagon line-coupled multi-body dynamics model with 73 degrees of freedom. And the reasonableness of the line-coupled dynamics model is verified by using the maximum residual acceleration, the nonlinear critical speed of the wagon. The experimental results show that the established vehicle line coupling dynamics model meets the requirements of vehicle line coupling dynamics modeling.

Diagenetic fluid evolution and water-rock interaction model of carbonate cements in sandstone: An example from the reservoir sandstone of the Fourth Member of the Xujiahe Formation of the Xiaoquan-Fenggu area, Sichuan Province, China

Carbonate cement is the most abundant cement type in the Fourth Member of the Xujiahe Formation in the Xiaoquan-Fenggu area of the West Sichuan Depression. Here we use a systematic analysis of carbonate cement petrology, mineralogy, carbon and oxygen isotope ratios and enclosure homogenization temperatures to study the precipitation mechanism, pore fluid evolu- tion, and distribution of different types of carbonate cement in reservoir sand in the study area. Crystalline calcite has relatively heavy carbon and oxygen isotope ratios （δ13C = 2.14%o, 8180 = -5.77‰）, and was precipitated early. It was precipitated di- rectly from supersaturated alkaline fluid under normal temperature and pressure conditions. At the time of precipitation, the fluid oxygen isotope ratio was very light, mainly showing the characteristics of a mixed meteoric water-seawater fluid（ δ180 = -3‰）, which shows that the fluid during precipitation was influenced by both meteoric water and seawater. The calcite cement that fills in the secondary pores has relatively lighter carbon and oxygen isotope ratios （δ13C = -2.36%0, 8180 = -15.68‰）. This cement was precipitated late, mainly during the Middle and Late Jurassic. An important material source for this carbonate cement was the feldspar corrosion process that involved organic matter. The Ca2＋, Fe3＋ and Mg2＋ ions released by the clay mineral transformation process were also important source materials. Because of water-rock interactions during the buri- al process, the oxygen isotope ratio of the fluid significantly increased during precipitation, by about 3‰. The dolomite ce- ments in calcarenaceous sandstone that was precipitated during the Middle Jurassic have heavier carbon and oxygen isotope ratios, which are similar to those of carbonate debris in the sandstone （δ13C = 1.93%o, δ180 = -6.11‰）, demonstrating that the two are from the same source that had a heavier oxygen isotope ratio （δ180 of about 2.2‰）. The differences in fluid oxygen isotope ratios during cement precipitation reflect the influences of different water-rock interaction systems or different wa- ter-rock interaction strengths. This is the main reason why the sandstone containing many rigid particles （lithic quartz sand- stone） has a relatively negative carbon isotope ratio and why the precipitation fluid in calcarenaceous sandstone has a relatively heavier oxygen isotope ratio.

GIS-Hydrogeochemical Model of the YaoundéFractured Rock Aquifer, Cameroon: Aquifer Setting, Seasonal Variations in Groundwater-Rock Interaction and Water Quality

This study of the gneiss-fractured-rock aquifer in Yaoundé capital of Cameroon determines: the aquifer setting-flow systems, the aquifer type, seasonal variations in rock-water interactions, evolution of the hydrogeochemical processes, physicochemical parameters and the suitability for domestic-agro-industrial use of the groundwater. Physicochemical field tests were carried out on 445 wells during four seasons for EC, pH, TDS, Temperature and static water level from July 2016 to May 2017. 90 well samples were analyzed 45 samples per season: wet/dry. 38 borewell logs were used together with structural data to determine the aquifer setting. The field physico-chemical and laboratory analysis data of well samples were mounted unto various GIS software platforms: Global mapper, AqQa, Aquachem, Rockworks, Logplot7, Surfer and ArcGIS, to get indices/parameters/figures, by use of Durov’s, Piper’s and Gibbs diagrams, Water quality index WQI, USSL ratio, Sodium Absorption ratio SAR, Percent sodium %Na, Kelly Ratio KR, Magnesium Absorption Ratio MAR, Total Hardness TH, Residual Sodium Carbonate RSC and Permeability Index PI that were determined. The process of groundwater ions acquisition is three-fold: by recharge through atmospheric precipitation, by ion exchange/simple dissolution between the rock-groundwater and by groundwater mixing in its flow path. Water types are Ca-HCO3, Mg-HCO3 and Mg-Cl while hydrogeochemical facies are Ca-Mg-HCO3 and Ca-Mg-Cl-SO4. Most water samples are fresh, potable and soft all seasons. The hydrogeological conceptual model is that of a three-layered single phreatic fractured-rock-aquifer while other researchers postulated a two-aquifer, phreatic and semi-confined, two-layered model.

Application of molecular interaction volume model in separation of Pb-Sn-Sb ternary alloy by vacuum distillation

Based on the molecular interaction volume model （MIVM）, the activities of components of Pb Sn Sb ternary alloy were predicted. The vapo^liquid phase equilibrium of Pb-Sn-Sb alloy system was calculated using the activity coefficients of Pb Sn-Sb alloy system in the process of vacuum distillation. The calculated results show that the content of Sn in vapor phase increases with the increasing distillation temperature and content of Sn in liquid phase. However, the content of Sn in vapor phase is only 0.45% （mass fraction） while 97% in liquid phase at 1100 ℃, which shows that the separating effect is very well. Experimental investigations on the separation of Pb-Sn-Sb ternary alloy were carried out in the distillation temperature range of 1100-1300 ℃ under vacuum condition. It is found that the Sn content in vapor phase is 0.54% while 97% in liquid phase at 1100 ℃. Finally, the predicted data were compared with the experimental results showing good agreement with each other.

Analysis of Genetic Effects of Nuclear-Cytoplasmic Interaction on Quantitative Traits:Genetic Model for Diploid Plants

A genetic model was proposed for simultaneously analyzing genetic effects of nuclear, cytoplasm, and nuclear-cytoplasmic interaction （NCI） as well as their genotype by environment （GE） interaction for quantitative traits of diploid plants. In the model, the NCI effects were further partitioned into additive and dominance nuclear-cytoplasmic interaction components. Mixed linear model approaches were used for statistical analysis. On the basis of diallel cross designs, Monte Carlo simulations showed that the genetic model was robust for estimating variance components under several situations without specific effects. Random genetic effects were predicted by an adjusted unbiased prediction （AUP） method. Data on four quantitative traits （boll number, lint percentage, fiber length, and micronaire） in Upland cotton （Gossypium hirsutum L.） were analyzed as a worked example to show the effectiveness of the model.

Groundwater monitoring of an open-pit limestone quarry:Water-rock interaction and mixing estimation within the rock layers by geochemical and statistical analyses

Water-rock interaction and groundwater mixing are important phenomena in understanding hydrogeological systems and the stability of rock slopes especially those consisting largely of moderately watersoluble minerals like calcite. In this study, the hydrogeological and geochemical evolutions of groundwater in a limestone quarry composed of three strata: limestone layer(covering), interbedded layer under the covering layer, and slaty greenstone layer(basement) were investigated. Water-rock interaction in the open-pit limestone quarry was evaluated using PHREEQC, while hierarchical cluster analysis(HCA)and principal component analysis(PCA) were used to classify and identify water sources responsible for possible groundwater mixing within rock layers. In addition, Geochemist's Workbench was applied to estimate the mixing fractions to clarify sensitive zones that may affect rock slope stability. The results showed that the changes in Ca2+and HCO3àconcentrations of several groundwater samples along the interbedded layer could be attributed to mixing groundwater from the limestone layer and that from slaty greenstone layer. Based on the HCA and PCA results, groundwaters were classified into several types depending on their origin:(1) groundwater from the limestone layer(LO),(2) mixed groundwater flowing along the interbedded layer(e.g., groundwater samples L-7, L-11, S-3 and S-4), and(3) groundwater originating from the slaty greenstone layer(SO). The mixing fractions of 41% LO: 59% SO, 64% LO: 36% SO, 43%LO: 57% SOand 25% LO: 75% SOon the normal days corresponded to groundwaters L-7, L-11, S-3 and S-4,respectively, while the mixing fractions of groundwaters L-7 and L-11(61% LO: 39% SOand 93% LO: 7% SO,respectively) on rainy days became the majority of groundwater originating from the limestone layer.These indicate that groundwater along the interbedded layer significantly affected the stability of rock slopes by enlarging multi-breaking zones in the layer through calcite dissolution and inducing high water pressure, tension cracks and potential sliding plane along this layer particularly during intense rainfall episodes.

Dynamic Analysis of the Seafloor Pilot Miner Based on Single-Body Vehicle Model and Discretized Track-Terrain Interaction Model

In order to achieve the complex dynamic analysis of the self-propelled seafloor pilot miner moving on the seafloor of extremely cohesive soft soil and further to make it possible to integrate the miner system with some subsystems to form the complete integrated deep ocean mining pilot system and perform dynamic analysis, a new method for the dynamic modeling and analysis of the miner is proposed and developed in this paper, resulting in a simplified 3D single-body vehicle model with three translational and three rotational degrees of freedom, while the track-terrain interaction model is built by partitioning the track-terrain interface into discrete elements with parameterized force dements built on the theory of terramechanics acting on each discrete dement. To evaluate and verify the correctness and effectiveness of this new modeling and analysis method, typical comparative studies with regard to computational efficiency and solution accuracy are carried out between the traditional modeling method of building the tracked vehicle as a multi-body model and the new modeling method. In full consideration of the particMar structure design of the pilot miner, the special characteristics of the seafioor soil and the hydrodynamic force of near-seafloor currnt, the dynamic simulation analysis of the miner is performed and discussed, which can provide useful guidance and reference for the practical miner system in design and operation. This new method can not only realize the rapid dynamic simulation analysis of the miner but also make possible the integration and rapid dynamic analysis of the complete integrated deep ocean mining pilot system in further researches.

Test of subcritical crack growth and fracture toughness under water-rock interaction in three types of rocks

The subcritical crack growth and fracture toughness in peridotite, lherzolite and amphibolite were investigated with double torsion test. The results show that water-rock interaction has a significant influence on subcritical crack growth. With water-rock interaction, the crack velocity increases, while the stress intensity factor declines, which illustrates that water-rock interaction can decrease the strength of rocks and accelerate the subcritical crack growth. Based on Charlse theory and Hilling & Charlse theory, the test data were analyzed by regression and the correlation coefficients were all higher than 0.7, which shows the correlation is significant. This illustrates that both theories can explain the results of tests very well. Therefore, it is believed that the subcritical crack growth attributes to the breaking of chemical bond, which is caused by the combined effect of the tensile stress and the chemical reaction between the material at crack tip and the corrosive agent. Meanwhile, water-rock interaction has a vital effect on fracture toughness. The fracture toughness of samples under atmospheric environment is higher than that of samples immersed in water. And water-rock interaction has larger influence on fracture toughness in amphibolite than that in peridotite and lherzolite.

INTERACTION MODELS FOR EFFECTIVE THERMAL AND ELECTRIC CONDUCTIVITIES OF CARBON NANOTUBE COMPOSITES

The present article provides supplementary information of previous works of analytic models for predicting conductivity enhancements of carbon nanotube composites. The models, though fairly simple, are able to take account of the effects of conductivity anisotropy, nonstraightness, and aspect ratio of the CNT additives on the conductivity enhancement of the composite and to give predictions agreeing well with existing experimental data. The omitted detailed derivation of this model is demonstrated in the present article with a more systematical analysis, which may help with further development in this direction. Furthermore, the effects of various orientation distributions of CNTs are reported here for the first time. The information may be useful in design or fabrication technology of CNT composites for better or specified conductivities.

Maximal and total skew information for a two-qubit system using nonlinear interaction models

Maximal and total skew information is studied. For symmetric pure states of two-qubit, they are closely related to the linear entropy, the concurrence, and the spin squeezing parameter. For a two-qubit system implemented in three nonlinear interaction models with an external field, we give the exact state vectors and the expectation value （Sz） at any time t. Based on （Sz）2, we give the maximal and the total skew information and a condition in which the maximal and the total skew information can reach 1 and 2, respectively.

A NOTE ON THE INTERACTIONS OF ELEMENTARY WAVES FOR THE AR TRAFFIC FLOW MODEL WITHOUT VACUUM

In this note, we consider the interactions of elementary waves for the traffic flow model proposed by Aw and Rascle when the vacuum is not involved. The solutions are obtained constructively and globally when the initial data consist of three pieces of constant states. Furthermore, it can be found that the Riemann solutions are stable with respect to such small perturbations of the initial data in this particular situation by investigating the limits of the solutions as the perturbed parameter ε goes to zero.

The superiority of multi-trait models with genotype-by-environment interactions in a limited number of environments for genomic prediction in pigs

Background: Different production systems and climates could lead to genotype-by-environment(G × E) interactions between populations, and the inclusion of G × E interactions is becoming essential in breeding decisions. The objective of this study was to investigate the performance of multi-trait models in genomic prediction in a limited number of environments with G × E interactions.Results: In total, 2,688 and 1,384 individuals with growth and reproduction phenotypes, respectively, from two Yorkshire pig populations with similar genetic backgrounds were genotyped with the PorcineSNP80 panel.Single-and multi-trait models with genomic best linear unbiased prediction(GBLUP) and BayesC π were implemented to investigate their genomic prediction abilities with 20 replicates of five-fold cross-validation.Our results regarding between-environment genetic correlations of growth and reproductive traits(ranging from 0.618 to 0.723) indicated the existence of G × E interactions between these two Yorkshire pig populations. For single-trait models, genomic prediction with GBLUP was only 1.1% more accurate on average in the combined population than in single populations, and no significant improvements were obtained by BayesC π for most traits. In addition, single-trait models with either GBLUP or BayesC π produced greater bias for the combined population than for single populations. However, multi-trait models with GBLUP and BayesC π better accommodated G × E interactions,yielding 2.2% – 3.8% and 1.0% – 2.5% higher prediction accuracies for growth and reproductive traits, respectively,compared to those for single-trait models of single populations and the combined population. The multi-trait models also yielded lower bias and larger gains in the case of a small reference population. The smaller improvement in prediction accuracy and larger bias obtained by the single-trait models in the combined population was mainly due to the low consistency of linkage disequilibrium between the two populations, which also caused the BayesC π method to always produce the largest standard error in marker effect estimation for the combined population.Conclusions: In conclusion, our findings confirmed that directly combining populations to enlarge the reference population is not efficient in improving the accuracy of genomic prediction in the presence of G × E interactions, while multi-trait models perform better in a limited number of environments with G × E interactions.

BLOWUP CRITERION FOR THE COMPRESSIBLE FLUID-PARTICLE INTERACTION MODEL IN 3D WITH VACUUM

In this article, we consider the blowup criterion for the local strong solution to the compressible fluid-particle interaction model in dimension three with vacuum. We establish a BKM type criterion for possible breakdown of such solutions at critical time in terms of both the L^∞ （0, T; L^6）-norm of the density of particles and the ^L1（0, T; L^∞）-norm of the deformation tensor of velocity gradient.

Maximal and total skew information of three-qubit system obtained using nonlinear interaction models

Both the maximal and the total skew information have been studied. For a three-qubit system implemented in three nonlinear interaction models, we give the exact state vector at any time t. Beused on this, we give the maximal and the total skew information. It is found that they have the same form and their evolution periods are dependent on the energy difference between the ground state and the second excited state in these models. The maximal skew information is always in the （Sx, Sv） plane. We give the condition for the occurrence of IGHZ}sy, in which they can reach the extreme values of 9/4 and 15/4, respectively. In three different decoherence channels, two kinds of information and the concurrence are calculated. We find that the phenomenon of the concurrence of sudden death occurs, but the above two kinds of information do not die suddenly. In the phase-damping channel, the two kinds of information will not be lost completely.

Study on soil-pile-structure-TMD interaction system by shaking table model test

The success of the tuned mass damper (TMD) in reducing wind-induced structural vibrations has been well established. However, from most of the recent numerical studies, it appears that for a structure situated on very soft soil, soil-structure interaction (SSI) could render a damper on the structure totally ineffective. In order to experimentally verify the SSI effect on the seismic performance of TMD, a series of shaking table model tests have been conducted and the results are presented in this paper. It has been shown that the TMD is not as effective in controlling the seismic responses of structures built on soft soil sites due to the SSI effect. Some test results also show that a TMD device might have a negative impact if the SSI effect is neglected and the structure is built on a soft soil site. For structures constructed on a soil foundation, this research verifies that the SSI effect must be carefully understood before a TMD control system is designed to determine if the control is necessary and if the SSI effect must be considered when choosing the optimal parameters of the TMD device.

THE AVALANCHE DYNAMICS IN RANDOM NEAREST NEIGHBOR MODELS OF EVOLUTION WITH INTERACTION STRENGTH

A generalized Bak-Sneppen model （BS model） of biological evolution with intcraction strength θ is introduced in d-dimensional space, where the “nearest neighbors” are chosen among the 2d neighbors of the extremal site, with the probabilities rebated to the sizes of the fitnesses. Simulations of one- and two-dimensional models arc given.For given θ 〉 0, the model can self-organize, to a critical state, and the critical threshold fc（θ） decreases as θ increases. The exact gap equation depending on θ is presented, which reduces to the gap equation of BS model as θ tends to infinity. An exact cquation for the critical exponent γ（θ） is also obtained. Scaling relations are established among the six critical exponents of the avalanches of the model.

Pairwise thermal entanglement in a three-qubit Heisenberg XX model with a nonuniform magnetic field and Dzyaloshinski-Moriya interaction

Pairwise thermal entanglement in a three-qubit Heisenberg XX model is investigated when a nonuniform mag- netic field and the Dzyaloshinski-Moriya interaction are included. We find that the nonuniform magnetic field and Dzyaloshinski-Moriya interaction are the more efficient control parameters for the increase of entanglement and critical temperature. For both the nearest neighbour sites and the next nearest neighbour sites, the magnetic field can induce entanglement to a certain extent and the Dzyaloshinski-Moriya interaction can enhance the entanglement to a stable value. The steady value of the nearest neighbour site entanglement C12 is larger than the next nearest neighbour site entanglement C13. An interesting phenomenon is that the entanglement curve of C12 appears a peak value when the Dzyaloshinski-Moriya interaction is considered in a nonuniform magnetic field.