Rate transient analysis methods for water-producing gas wells in tight reservoirs with mobile water

Tight gas reservoirs with mobile water exhibit multi-phase flow and high stress sensitivity.Accurately analyzing the reservoir and well parameters using conventional single-phase rate transient analysis methods proves challenging.This study introduces novel rate transient analysis methods incorporating evaluation processes based on the conventional flowing material balance method and the Blasingame type-curve method to examine fractured gas wells producing water.By positing a gas-water two-phase equivalent homogenous phase that considers characteristics of mobile water,gas,and high stress sensitivity,the conventional single-phase rate transient analysis methods can be applied by integrating the phase's characteristics and defining the phase's normalized parameters and material balance pseudotime.The rate transient analysis methods based on the equivalent homogenous phase can be used to quantitatively assess the parameters of wells and gas reservoirs,such as original gas-in-place,fracture half-length,reservoir permeability,and well drainage radius.This facilitates the analysis of production dynamics of fractured wells and well-controlled areas,subsequently aiding in locating residual gas and guiding the configuration of well patterns.The specific evaluation processes are detailed.Additionally,a numerical simulation mechanism model was constructed to verify the reliability of the developed methods.The methods introduced have been successfully implemented in field water-producing gas wells within tight gas reservoirs containing mobile water.

Well interference evaluation considering complex fracture networks through pressure and rate transient analysis in unconventional reservoirs

Severe well interference through complex fracture networks(CFNs)can be observed among multi-well pads in low permeability reservoirs.The well interference analysis between multi-fractured horizontal wells(MFHWs)is vitally important for reservoir effective development.Well interference has been historically investigated by pressure transient analysis,while it has shown that rate transient analysis has great potential in well interference diagnosis.However,the impact of complex fracture networks(CFNs)on rate transient behavior of parent well and child well in unconventional reservoirs is still not clear.To further investigate,this paper develops an integrated approach combining pressure and rate transient analysis for well interference diagnosis considering CFNs.To perform multi-well simulation considering CFNs,non-intrusive embedded discrete fracture model approach was applied for coupling fracture with reservoir models.The impact of CFN including natural fractures and frac-hits on pressure and rate transient behavior in multi-well system was investigated.On a logelog plot,interference flow and compound linear flow are two new flow regimes caused by nearby producers.When both NFs and frac-hits are present in the reservoir,frac-hits have a greater impact on well#1 which contains frac-hits,and NFs have greater impact on well#3 which does not have frac-hits.For all well producing circumstances,it might be challenging to see divergence during pseudosteady state flow brought on by frac-hits on the logelog plot.Besides,when NFs occur,reservoir depletion becomes noticeable in comparison to frac-hits in pressure distribution.Application of this integrated approach demonstrates that it works well to characterize the well interference among different multi-fractured horizontal wells in a well pad.Better reservoir evaluation can be acquired based on the new features observed in the novel model,demonstrating the practicability of the proposed approach.The findings of this study can help for better evaluating well interference degree in multi-well systems combing PTA and RTA,which can reduce the uncertainty and improve the accuracy of the well interference analysis based on both field pressure and rate data.

Convergence Rate Analysis for Deep Ritz Method

Using deep neural networks to solve PDEs has attracted a lot of attentions recently.However,why the deep learning method works is falling far behind its empirical success.In this paper,we provide a rigorous numerical analysis on deep Ritz method(DRM)[47]for second order elliptic equations with Neumann boundary conditions.We establish the first nonasymptotic convergence rate in H^(1)norm for DRM using deep networks with ReLU^(2)activation functions.In addition to providing a theoretical justification of DRM,our study also shed light on how to set the hyperparameter of depth and width to achieve the desired convergence rate in terms of number of training samples.Technically,we derive bound on the approximation error of deep ReLU^(2)network in C^(1)norm and bound on the Rademacher complexity of the non-Lipschitz composition of gradient norm and ReLU^(2)network,both of which are of independent interest.

Prediction of cavity growth rate during underground coal gasification using multiple regression analysis

During underground coal gasification （UCG）, whereby coal is converted to syngas in situ, a cavity is formed in the coal seam. The cavity growth rate （CGR） or the moving rate of the gasification face is affected by controllable （operation pressure, gasification time, geometry of UCG panel） and uncontrollable （coal seam properties） factors. The CGR is usually predicted by mathematical models and laboratory experiments, which are time consuming, cumbersome and expensive. In this paper, a new simple model for CGR is developed using non-linear regression analysis, based on data from 1 l UCG field trials. The empirical model compares satisfactorily with Perkins model and can reliably predict CGR.

Study on Differential Rate Kinetics Analysis Based on the Substitution Reaction of Rare Earth-PHA with CyDTA

The kinetic behaviours of the substitution reaction of rare earth-PHA with CyDTA were studied systemati- cally.The relationship between the rate constant and atomic number was discussed.The rate differentiation val- ue R_d(R_d=lgk_(z+n)-lgk_z)was proposed to evaluate the possibility of differential kinetic analysis.The R_d value between the neighbouring lanthanide ions first increases and then decreases along with increasing atomic number, so that the middle and heavy rare earth mixture(such as Sm-Gd and Gd-Y)are ideal systems for the differential rate kinetic analysis.

Maximizing the Benefit of Rate Transient Analysis for Gas Condensate Reservoirs

In recent years,many trials have been made to use the Rate Transient Analysis(RTA)techniques as a method to describe the gas condensate reservoirs.The problem with using these techniques is the multi-phase behavior of the gas condensate reservoirs.Therefore,the Pressure Transient Analysis(PTA)is commonly used in this case to analyze the reservoir parameters.In this paper,we are going to compare the results of both PTA and RTA of three wells in gas condensate reservoirs.The comparison showed a great match between the results of the two mentioned techniques for the first time using a reference GOR of 75,000 SCF/STB.Therefore,we concluded that we could depend on RTA instead of PTA to spare the cost associated with the PTA in the gas condensate reservoirs.

QTL analysis of leaf photosynthetic rate and related physiological traits in rice(Oryza sativa L.)

Photosynthesis is one of the most important factors that influence the biomass and yield. Recently, more attention has been paid to genetic study on rice photosynthesis and rice breeding for the physiological traits related to high efficient photosynthesis. Chlorophyll content, stomatal resistance, and transpiration rate were very important physiological traits related to photosynthesis. But until now, no genetic study on these traits has been reported. A DH population derived from anther culture of ZYQ8/JX17, a typical indica/japonica hybrid was developed,

Analysis of State Homicide Rates Using Statistical Ranking and Selection Procedures

Nonparametric and parametric subset selection procedures are used in the analysis of state homicide rates (SHRs), for the year 2005 and years 2014-2020, to identify subsets of states that contain the “best” (lowest SHR) and “worst” (highest SHR) rates with a prescribed probability. A new Bayesian model is developed and applied to the SHR data and the results are contrasted with those obtained with the subset selection procedures. All analyses are applied within the context of a two-way block design.

A Positive Analysis on Personal Saving Rate between America and China

The level of saving not only influences the life of individuals, but also plays an important role in a country＇s development. Accordingly, the studying on saving is becoming a focus problem in modem life. In recent years, the personal saving rate in the United States has fallen sharply, but the personal saving rate in China is at an astoundingly high level. This paper studies this problem with the positive analysis method from the situation; the reasons of the saving rate disparity between the U.S. and .China, and put forward some proposals about how to deal with the saving problems.

Productivity analysis of horizontal wells intercepted by multiple finite-conductivity fractures

Horizontal wells in the anisotropic reservoirs can be stimulated by hydraulic fracturing in order to create multiple finite-conductivity vertical fractures. Several methods for evaluating the productivity of the horizontal wells have been presented in the literature. With such methods, however, it is still difficult to obtain an accurate result. This paper firstly presents the dimensionless conductivity theory of vertical fractures. Then models for calculating the equivalent wellbore radius and the skin factor due to flow convergence to the well bore are proposed after analyzing the steady-state flow in porous reservoirs. By applying the superposition principle to the pressure drop, a new method for evaluating the productivity of horizontal wells intercepted by multiple finite-conductivity fractures is developed. The influence of fracture conductivity and fracture half length on the horizontal well productivity is quantitatively analyzed with a synthetic case. Optimum fracture number and fracture space are further discussed in this study. The results prove that the method outlined here should be useful to design optimum fracturing of horizontal wells.

Effect of loading rate and time delay on the tangent modulus method(TMM)in coal and coal measured rocks

Non-destructive techniques of in-situ stress measurement from oriented cored rocks have great potential to be developed as a cost cost-effective and reliable alternative to the conventional overcoring and hydraulic fracturing methods.The tangent modulus method(TMM)is one such technique that can be applied to oriented cored rocks to measure in-situ stresses.Like the deformation rate analysis(DRA),the rock specimen is subjected to two cycles of uniaxial compression and the stress-tangent modulus curve for the two cycles is obtained from the stress-strain curve.A bending point in the tangent modulus curve of the first cycle is observed,separating it from the tangent modulus curve of the second cycle.The point of separation between the two curves is assumed to be the previously applied maximum stress.A number of experiments were conducted on coal and coal measured rocks(sandstone and limestone)to understand the effect of loading conditions and the time delay.The specimens were preloaded,and cyclic compressions were applied under three different modes of loading,four different strain rates,and time delays of up to one week.The bending point in the stress-tangent modulus curves occurred approximately at the applied pre-stress levels under all three loading modes,and no effect of loading rate was observed on the bending points in TMM.However,a clear effect of time delay was observed on the TMM,contradicting the DRA results.This could be due to the sensitivity of TMM and the range of its applicability,all of which need further investigation for the in-situ stress measurement.

Clustered Federated Learning with Weighted Model Aggregation for Imbalanced Data

As a promising edge learning framework in future 6G networks,federated learning(FL)faces a number of technical challenges due to the heterogeneous network environment and diversified user behaviors.Data imbalance is one of these challenges that can significantly degrade the learning efficiency.To deal with data imbalance issue,this work proposes a new learning framework,called clustered federated learning with weighted model aggregation(weighted CFL).Compared with traditional FL,our weighted CFL adaptively clusters the participating edge devices based on the cosine similarity of their local gradients at each training iteration,and then performs weighted per-cluster model aggregation.Therein,the similarity threshold for clustering is adaptive over iterations in response to the time-varying divergence of local gradients.Moreover,the weights for per-cluster model aggregation are adjusted according to the data balance feature so as to speed up the convergence rate.Experimental results show that the proposed weighted CFL achieves a faster model convergence rate and greater learning accuracy than benchmark methods under the imbalanced data scenario.

Sensitivity analysis of influencing parameters in cavern stability

In order to analyze the stability of the underground rock structures,knowing the sensitivity of geomechanical parameters is important.To investigate the priority of these geomechanical properties in the stability of cavern,a sensitivity analysis has been performed on a single cavern in various rock mass qualities according to RMR using Phase 2.The stability of cavern has been studied by investigating the side wall deformation.Results showed that most sensitive properties are coefficient of lateral stress and modulus of deformation.Also parameters of Hoek-Brown criterion and r c have no sensitivity when cavern is in a perfect elastic state.But in an elasto-plastic state,parameters of Hoek-Brown criterion and r c affect the deformability;such effect becomes more remarkable with increasing plastic area.Other parameters have different sensitivities concerning rock mass quality(RMR).Results have been used to propose the best set of parameters for study on prediction of sidewall displacement.

An investigation on dissolution kinetics of single sodium carbonate particle with image analysis method

Dissolution kinetics of sodium carbonate is investigated with the image analysis method at the approach of single particle.The dissolution experiments are carried out in an aqueous solution under a series of controlled temperature and p H.The selected sodium carbonate particles are all spherical with the same mass and diameter.The dissolution process is quantified with the measurement of particle diameter from dissolution images.The concentration of dissolved sodium carbonate in solvent is calculated with the measured diameter of particle.Both surface reaction model and mass transport model are implemented to determine the dissolution mechanism and quantify the dissolution rate constant at each experimental condition.According to the fitting results with both two models,it is clarified that the dissolution process at the increasing temperature is controlled by the mass transport of dissolved sodium carbonate travelling from particle surface into solvent.The dissolution process at the increasing pH is controlled by the chemical reaction on particle surface.Furthermore,the dissolution rate constant for each single spherical sodium carbonate particle is quantified and the results show that the dissolution rate constant of single spherical sodium carbonate increases significantly with the rising of temperature,but decreases with the increasing of pH conversely.

ANALYSIS OF THE TRENDS OF THUNDERSTORMS IN 1951-2007 IN JIANGSU PROVINCE

Based on the 1951-2007 thunderstorms in Jiangsu,a study is conducted for their climate trends,periodicity,spatiotemporal patterns,and the distributions of the first and last days of the thunderstorms at different guarantee rates (GRs) using climate tendency rate,wavelet analysis,and GR for diagnosis.Results suggest that the inter-annual number of thunderstorm days (TSDs) exhibits a decreasing trend in this province.The trend is displayed mainly in the decreasing TSD number in summer and autumn except in spring,when the variation is not significant in the study period.In this province,the TSD number declines by ～2 days per 10 years.On an inter-annual basis,the pronounced positive departures of the number take place chiefly in the early 1960s,the late 1960s to the early-mid-1970s,the late 1980s,and the late 1990s compared with the negative anomalies dominant in the late 1970s to the mid-1980s,the mid-to-late-1990s,and the late 1990s to 2007.There are vast differences in the initial and ending days at diverse GRs in different areas of the province.At 50% GR,the earliest (last) days occur from mid-March to early April (early to late September) while at 80% GR,the initial (last) days are from late March to early May (early to late October).For the distribution of periods,the periods >8-10 years are relatively stable for the entire province.Based on 1951-2007 period analysis,the region north (south) of the Huaihe River experiences TSDs less (more) than normal days in recent years.

Conscious Slower Breathing Predominates Parasympathetic Activity and Provides a Relaxing Effect, in Healthy Japanese Adult Women

Background: The optimal breathing pattern (BP) to effectively regulate autonomic nervous activity is yet to be determined. Objective: We aimed to clarify the effects of four BPs (BP-1, BP-2, BP-3, and BP-4) on autonomic nervous activity and mood changes. Methods: Eleven healthy adult female volunteers performed each BP in a sitting position for 5 min in a resting state. The time required for one breathing for BP-1 (30 breaths/min), BP-2 (20 breaths/min), BP-3 (15 breaths/min), and BP-4 (10 breaths/min) were 2 s, 3 s, 4 s, and 6 s, respectively. The inspiratory/expiratory time of one breathing was 1 s/1 s, 1 s/2 s, 2 s/2 s, and 2 s/4 s. The high-frequency component (HF) and low-frequency component (LF)/HF ratio during and before (control) performing a BP were calculated from heart rate variability data recorded using the wearable biometric information tracer M-BIT. Three mood changes, which are, “pleasure—unpleasure”, “relaxation—tension”, and “sleepiness—arousal”, in the subjects were assessed using the visual analog scale (VAS) before and after performing a BP. Results: Slower breathing induced an increase in HF power and a reduction in LF/HF ratio, indicating increased parasympathetic activity and decreased sympathetic dominance. Furthermore, VAS revealed that slower breathing increased the tendency to feel “pleasure”, “relaxation”, and “sleepiness”. Conclusion: Our results suggest that slower breathing predominates parasympathetic activity in the autonomic nervous system, resulting in a relaxing effect. This result may help lay the foundation for deriving breathing methods that efficiently regulate an individual’s autonomic activity.

Production performance analysis of a continental shale oil reservoir in Bohai Bay basin

Due to the extremely low permeability of shale formations,the combination of horizontal well and volume fracturing has been proposed as an effective technique to improve the production of Dagang continental shale oil reservoirs.Based on the flow material balance method(FMB)and straight-line analysis(SLA)method,the stimulated reservoir volume(SRV)and drainage volume are determined to identify the flow regimes of the seepage mechanism of shale oil reservoirs.To resolve the challenges of multi-scaled flow regimes and bottom hole pressure(BHP)variation before and after pumping in shale oil wells,a multi-linear analytical flow model was established to predict the future production and the final expected ultimate recoverable oil(EURo)after fitting the historical production dynamics.Based on the results,it can be concluded that the flow regime of a shale oil well in production can be divided into two stages consisting of linear flow within SRV and composite flow from the un-stimulated area to SRV.The effects of fracturing operation parameters,such as fracturing fluid volume and sand/liquid ratio,on shale oil productivity,are analyzed,and insightful suggestions are drawn for the future development of this pay zone.

Power Allocation for NOMA in D2D Relay Communications

Non-orthogonal multiple access(NOMA)is considered as one of the key technologies for the fifth generation(5G)wireless communications.The integration of NOMA and device-to-device(D2D)communications has recently attracted wide attention.In this paper,a relaying D2D communications assisted with cooperative relaying systems using NOMA(DRC-NOMA)is considered.We analyze the ergodic sum-rate for the proposed system and then derive the closed-form expressions.In addition,an optimal power allocation strategy maximizing the ergodic sum-rate is proposed based on these analysis results.Numerical results show the good agreement between the results of analysis and Monte Carlo method.The proposed DRC-NOMA has a great improvement of the ergodic sum-rate in the small regime of average channel gain of D2D pair.

Numerical study of AE and DRA methods in sandstone and granite in orthogonal loading directions

The directional dependency of the acoustic emission （AE） and deformation rate analysis （DRA） methods was analyzed, based on the contact bond model in the two-dimensional particle flow code （PFC2D） in two types of rocks, the coarse-grained sandstone and Aue granite. Each type of rocks had two shapes, the Brazilian disk and a square shape. The mechanical behaviors of the numerical model had already been verified to be in agreement with those of the physical specimens in previous research. Three loading protocols with different loading cycles in two orthogonal directions were specially designed in the numerical tests. The results show that no memory effect is observed in the second loading in the orthogonal direction. However, both the cumulative crack number of the second loading and the differential strain value at the inflection point are influenced by the first loading in the orthogonal direction.