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.

Numerical Simulation on Radon Retardation Behavior of Covering Floats in Radon-Containing Water

Objective This study aimed to efficiently reduce the release of radon from water bodies to protect the environment.Methods Based on the sizes of the experimental setup and modular float,computational fluid dynamics(CFD)was used to assess the impact of the area coverage rate,immersion depth,diffusion coefficient,and radon transfer velocity at the gas–liquid interface on radon migration and exhalation of radon-containing water.Based on the numerical simulation results,an estimation model for the radon retardation rate was constructed.The effectiveness of the CFD simulation was evaluated by comparing the experimental and simulated variation values of the radon retardation rate with the coverage area rates.Results The effect of radon transfer velocity on radon retardation in water bodies was minor and insignificant according to the appropriate value;therefore,an estimation model of the radon retardation rate of the coverage of a radon-containing water body was constructed using the synergistic impacts of three factors:area coverage rate,immersion depth,and diffusion coefficient.The deviation between the experimental and simulated results was<4.3%.Conclusion Based on the numerical simulation conditions,an estimation model of the radon retardation rate of covering floats in water bodies under the synergistic effect of multiple factors was obtained,which provides a reference for designing covering floats for radon retardation in radoncontaining water.

Influence of O-O formation pathways and charge transfer mediator on lipid bilayer membrane-like photoanodes for water oxidation

Inspired by the function of crucial components in photosystemⅡ(PSⅡ),electrochemical and dyesensitized photoelectrochemical(DSPEC)water oxidation devices were constructed by the selfassembly of well-designed amphipathic Ru(bda)-based catalysts(bda=2,2'-bipyrdine-6,6'-dicarbonoxyl acid)and aliphatic chain decorated electrode surfaces,forming lipid bilayer membrane(LBM)-like structures.The Ru(bda)catalysts on electrode-supported LBM films demonstrated remarkable water oxidation performance with different O-O formation mechanisms.However,compared to the slow charge transfer process,the O-O formation pathways did not determine the PEC water oxidation efficiency of the dyesensitized photoanodes,and the different reaction rates for similar catalysts with different catalytic paths did not determine the PEC performance of the DSPECs.Instead,charge transfer plays a decisive role in the PEC water oxidation rate.When an indolo[3,2-b]carbazole derivative was introduced between the Ru(bda)catalysts and aliphatic chain-modified photosensitizer in LBM films,serving as a charge transfer mediator for the tyrosine-histidine pair in PSⅡ,the PEC water oxidation performance of the corresponding photoanodes was dramatically enhanced.

Towards a new avenue for rapid synthesis of electrocatalytic electrodes via laser-induced hydrothermal reaction for water splitting

Electrochemical production of hydrogen from water requires the development ofelectrocatalysts that are active,stable,and low-cost for water splitting.To address these challenges,researchers are increasingly exploring binder-free electrocatalytic integratedelectrodes (IEs) as an alternative to conventional powder-based electrode preparation methods,for the former is highly desirable to improve the catalytic activity and long-term stability for large-scale applications of electrocatalysts.Herein,we demonstrate a laser-inducedhydrothermal reaction (LIHR) technique to grow NiMoO4nanosheets on nickel foam,which is then calcined under H2/Ar mixed gases to prepare the IE IE-NiMo-LR.This electrode exhibits superior hydrogen evolution reaction performance,requiring overpotentials of 59,116 and143 mV to achieve current densities of 100,500 and 1000 mA·cm-2.During the 350 h chronopotentiometry test at current densities of 100 and 500 m A·cm-2,the overpotentialremains essentially unchanged.In addition,NiFe-layered double hydroxide grown on Ni foam is also fabricated with the same LIHR method and coupled with IE-NiMo-IR to achieve water splitting.This combination exhibits excellent durability under industrial current density.The energy consumption and production efficiency of the LIHR method are systematicallycompared with the conventional hydrothermal method.The LIHR method significantly improves the production rate by over 19 times,while consuming only 27.78%of the total energy required by conventional hydrothermal methods to achieve the same production.

Gas-Water Production of a Continental Tight-Sandstone Gas Reservoir under Different Fracturing Conditions

A numerical model of hydraulic fracture propagation is introduced for a representative reservoir(Yuanba continental tight sandstone gas reservoir in Northeast Sichuan).Different parameters are considered,i.e.,the interlayer stress difference,the fracturing discharge rate and the fracturing fluid viscosity.The results show that these factors affect the gas and water production by influencing the fracture size.The interlayer stress difference can effectively control the fracture height.The greater the stress difference,the smaller the dimensionless reconstruction volume of the reservoir,while the flowback rate and gas production are lower.A large displacement fracturing construction increases the fracture-forming efficiency and expands the fracture size.The larger the displacement of fracturing construction,the larger the dimensionless reconstruction volume of the reservoir,and the higher the fracture-forming efficiency of fracturing fluid,the flowback rate,and the gas production.Low viscosity fracturing fluid is suitable for long fractures,while high viscosity fracturing fluid is suitable for wide fractures.With an increase in the fracturing fluid viscosity,the dimensionless reconstruction volume and flowback rate of the reservoir display a non-monotonic behavior,however,their changes are relatively small.

Optimization of sowing date and seeding rate for high winter wheat yield based on pre-winter plant development and soil water usage in the Loess Plateau,China

Sowing date and seeding rate are critical for productivity of winter wheat(Triticum aestivum L.).A three-year field experiment was conducted with three sowing dates(20 September(SD1),1 October(SD2),and 10 October(SD3)) and three seeding rates(SR67.5,SR90,and SR112.5) to determine suitable sowing date and seeding rate for high wheat yield.A large seasonal variation in accumulated temperature from sowing to winter dormancy was observed among three growing seasons.Suitable sowing dates for strong seedlings before winter varied with the seasons,that was SD2 in 2012–2013,SD3 in 2013–2014,and SD2 as well as SD1 in 2014–2015.Seasonal variation in precipitation during summer fallow also had substantial effects on soil water storage,and consequently influenced grain yield through soil water consumption from winter dormancy to maturity stages.Lower consumption of soil water from winter dormancy to booting stages could make more water available for productive growth from anthesis to maturity stages,leading to higher grain yield.SD2 combined with SR90 had the lowest soil water consumption from winter dormancy to booting stages in 2012–2013 and 2014–2015; while in 2013–2014,it was close to that with SR67.5 or SR112.5.For productive growth from anthesis to maturity stages,SD2 with SR90 had the highest soil water consumption in all three seasons.The highest water consumption in the productive growth period resulted in the best grain yield in both low and high rainfall years.Ear number largely contributed to the seasonal variation in grain yield,while grain number per ear and 1 000-grain weight also contributed to grain yield,especially when soil water storage was high.Our results indicate that sowing date and seeding rate affect grain yield through seedling development before winter and also affect soil water consumption in different growth periods.By selecting the suitable sowing date(1 October) in combination with the proper seeding rate of 90 kg ha–1,the best yield was achieved.Based on these results,we recommend that the current sowing date be delayed from 22 or 23 September to 1 October.

Effects of water intrusion and loading rate on mechanical properties of and crack propagation in coal–rock combinations

Tackling the problems of underground water storage in collieries in arid regions requires knowledge of the effect of water intrusion and loading rate on the mechanical properties of and crack development in coal–rock combinations. Fifty-four coal–rock combinations were prepared and split equally into groups containing different moisture contents(dry, natural moisture and saturated) to conduct acoustic emission testing under uniaxial compression with loading rates ranging from 0.1 mm/min to 0.6 mm/min. The results show that the peak stress and strength-softening modulus, elastic modulus, strain-softening modulus, and post-peak modulus partly decrease with increasing moisture content and loading rate. In contrast, peak strain increases with increasing moisture content and fluctuates with rising loading rate. More significantly, the relationship between stiffness and stress, combined with accumulated counts of acoustic emission, can be used to precisely predict all phases of crack propagation. This is helpful in studying the impact of moisture content and loading rate on crack propagation and accurately calculating mechanical properties. We also determined that the stress thresholds of crack closure, crack initiation, and crack damage do not vary with changes of moisture content and loading rate, constituting 15.22%, 32.20%, and 80.98% of peak stress, respectively. These outcomes assist in developing approaches to water storage in coal mines, determining the necessary width of waterproof coal–rock pillars, and methods of supporting water-enriched roadways, while also advances understanding the mechanical properties of coal–rock combinations and laws of crack propagation.

Relationship between Formation Water Rate,Equivalent Penetration Rate and Volume Flow Rate of Air in Air Drilling

Formation water invasion is the most troublesome problem associated with air drilling. However, it is not economical to apply mist drilling when only a small amount of water flows into wellbore from formation during air drilling. Formation water could be circulated out of the wellbore through increasing the gas injection rate. In this paper, the Angel model was modified by introducing Nikurade friction factor for the flow in coarse open holes and translating formation water rate into equivalent penetration rate. Thus the distribution of annular pressure and the relationship between minimum air injection rate and formation water rate were obtained. Real data verification indicated that the modified model is more accurate than the Angel model and can provide useful information for air drilling.

Prediction of Trend between Water Environment Pollution of D Lake and Death Rate of Malignancy in Population

Grey system analysis method was used to study the correlation between water pollution in D Lake area and death rate of malignancy with death rate of malignancy as effect sequence and a variety of water pollution index as factor sequence. On the basis of grey correlation analysis, grey system predication model was established for death rate of malignancy in population in D Lake area including GM (1, N) model for death rate of malignancy [ MR (t+1) =(9.9987E 1+5.0001E 2 +10.8994E 3+1.1114E 4+165.1029) ·e -0.0070t -9.9987E 1-5.0001E 2-10.8994E 3-1.1114E 4 ] and GM (1, 1) model for related factors [ E 1(t+1) =52.1214-46.9468e -0.0058t , E 2(t+1) =4.6114-4.5664e 0.0015t, E 3(t+1) =1.1389-1.1212e 0.0065t , E 4(t+1) = 554.5867-549.8006e 0.0016t ], and the trend of death rate of malignancy from 2000 to 2010 was predicted.

EFFECTS OF TEMPERATURE AND DISSOLVED OXYGEN CONTENT ONOXYGEN CONSUMPTION RATE OF CHINESE PRAWN, GIANT TIGER PRAWN AND GIANT FRESHWATER PRAWN

temperature and the diasolved oxygen content affect the oxygen consumption of juveniles of Chinese prawn (Penaeus chinensis), giant tiger prawn (P. monodon) and giant freshwater prawn(Macrobrachium rosenbergii). There is good correlation between the oxygen consumption rate (V, mg/g·h) of the above three prawn species and the water temperature, and dissolved oxygen. In the range of test temperature, V increased with water temperature and diassolved oxygen content. The V of the above three prawn species increased 0.085 mg/g·h, 0. 093 mg/g·h and 0. 08 mg/g·h respectively with each ℃ of rising temperature. The comatose point and stifling point of the juveniles rose obviously at unsuitable temperature.

Leakage Rate Model of Urban Water Supply Networks Using Principal Component Regression Analysis

To analyze the factors affecting the leakage rate of water distribution system, we built a macroscopic "leakage rate–leakage factors"(LRLF) model. In this model, we consider the pipe attributes(quality, diameter,age), maintenance cost, valve replacement cost, and annual average pressure. Based on variable selection and principal component analysis results, we extracted three main principle components—the pipe attribute principal component(PAPC), operation management principal component, and water pressure principal component. Of these, we found PAPC to have the most influence. Using principal component regression, we established an LRLF model with no detectable serial correlations. The adjusted R2 and RMSE values of the model were 0.717 and 2.067, respectively.This model represents a potentially useful tool for controlling leakage rate from the macroscopic viewpoint.

Surface warming patterns dominate the uncertainty in global water vapor plus lapse rate feedback

Climate feedbacks have been usually estimated using changes in radiative effects associated with increased global-mean surface temperature. Feedback uncertainties, however, are not only functions of global-mean surface temperature increase. In projections by global climate models, it has been demonstrated that the geographical variation of sea surface temperature change brings significant uncertainties into atmospheric circulation and precipitation responses at regional scales. Here we show that the spatial pattern of surface warming is a major contributor to uncertainty in the combined water vapour-lapse rate feedback. This is demonstrated by computing the global-mean radiative effects of changes in air temperature and relative humidity simulated by 31 climate models using a methodology based on radiative kernels. Our results highlight the important contribution of regional climate change to the uncertainty in climate feedbacks, and identify the regions of the world where constraining surface warming patterns would be most effective for higher skill of climate projections.

Effects of water saturation and loading rate on direct shear tests of andesite

For estimating the long-term stability of underground framework,it is vital to learn the mechanical and rheological characteristics of rock in multiple water saturation conditions.However,the majority of previous studies explored the rheological properties of rock in air-dried and water saturated conditions,as well as the water effects on compressive and tensile strengths.In this study,andesite was subjected to direct shear tests under five water saturation conditions,which were controlled by varying the wetting and drying time.The tests were conducted at alternating displacement rates under three vertical stresses.The results reveal that the shear strength decreases exponentially as water saturation increases,and that the increase in shear strength with a tenfold increase in displacement rate is nearly constant for each of the vertical stresses.Based on the findings of the shear tests in this study and the compression and tension tests in previous studies,the influences of both water saturation and loading rate on the Hoek-Brown failure criterion for the andesite was examined.These results indicate that the brittleness index of the andesite,which is defined as the ratio of uniaxial compressive strength to tensile strength,is independent of both water saturation and loading rate and that the influences of the water saturation dependence and the loading rate dependence of the failure criterion can be converted between each other.

The critical rate of horizontal wells in bottom-water reservoirs with an impermeable barrier

Barrier impacts on water cut and critical rate of horizontal wells in bottom water-drive reservoirs have been recognized but not investigated quantitatively. Considering the existence of impermeable barriers in oil formations, this paper developed a horizontal well flow model and obtained mathematical equations for the critical rate when water cresting forms in bottom-water reservoirs. The result shows that the barrier increases the critical rate and delays water breakthrough. Further study of the barrier size and location shows that increases in the barrier size and the distance between the barrier and oil-water contact lead to higher critical rates. The critical rate gradually approaches a constant as the barrier size increases. The case study shows the method presented here can be used to predict the critical rate in a bottom-water reservoir and applied to investigate the water cresting behavior of horizontal wells.

Reuse rate of treated wastewater in water reuse system

A water quality model for water reuse was made by mathematics induction. The relationship among the reuse rate of treated wastewater（R）, pollutant concentration of reused water（ Cs ）, pollutant concentration of influent（ C0）, removal efficiency of pollutant in wastewater（ E）, and the standard of reuse water were discussed in this study. According to the experiment result of a toilet wastewater treatment and reuse with membrane bioreactors, R would be set at less than 40%, on which all the concerned parameters could meet with the reuse water standards. To raise R of reuse water in the toilet, an important way was to improve color removal of the wastewater.

Variability of subduction rates of the subtropical North Pacific mode waters

The climatology subduction rate for the entire Pacific is known, but the mechanism of interannual to decadal variation remains unclear. In this study, we calculated the annual subduction rates of three types of North Pacific subtropical mode waters using a general circulation model (LICOM1.0) for the period of 1958-2001. The model experiments focused on interannual variations of ocean dynamical processes under daily wind forcings and seasonal heat fluxes. The mode water formation region was defined by a potential vorticity minimum at outcrop locations. The model results show that two subduction rate maxima (>100 m/a) were located in the Subtropical Mode Water (STMW) and the Central Mode Water (CMW) formation regions. These regions are consistent with a climatologically calculated value. The subduction rate in the Eastern Subtropical Mode Water (ESTMW) formation region was smaller at about 75 m/a. The subduction rate shows clear interannual and decadal variations associated with oceanic dynamic variabilities. The average subduction rate of the STMW was much smaller during the period of 1981-1990 compared with other periods, while that of the CMW had a negative anomaly before 1975 and a positive anomaly after 1978. The variability agreed with Ekman and geostrophic advections and mixed layer depths. The interannual variability of the subduction rate for the ESTMW was smallest during 1970-1990, as a result of a weak wind stress curl. This paper explores how interannual signals from the atmosphere are stored in different parts of the ocean, and thus may contribute to a better understanding of feedback mechanisms for the Pacific Decadal Oscillation (PDO) event.

A study of Indian Ocean Subtropical Mode Water: subduction rate and water characteristics

The annual subduction rate in the South Indian Ocean was calculated by analyzing Simple Ocean Data Assimilation （SODA） outputs in the period of 1950-2008. The subduction rate census for potential density classes showed a peak corresponding to Indian Ocean subtropical mode water （IOSTMW） in the southwestern part of the South Indian Ocean subtropical gyre. The deeper mixed layer depth, the sharper mixed-layer fronts and the associated relatively faster circulation in the present climatology resulted in a larger lateral induction, which primarily dominants the IOSTMW subduction rate, while with only minor contribution from vertical pumping. Without loss of generality, through careful analysis of the water characteristics in the layer of minimum vertical temperature gradient （LMVTG）, the authors suggest that the IOSTMW was identified as a thermostad, with a lateral minimum of low potential vorticity （PV, less than 200× 10^-12 m^-1·s^-1） and a low dT/dz （less than 1.5℃/（100 m））. The IOSTMW within the South Indian Ocean subtropical gyre distributed in the region approximately from 25° to 50° E and from 30° to 39°S. Additionally, the average characteristics （temperature, salinity, potential density） of the mode water were estimated about （16.38 ± 0.29）℃, （35.46 ±0.04）, （26.02 ±0.04） ae over the past 60 years.

Improvement of Water Use Efficiency in Winter Wheat byBreeding Lines with Low Rate of Water Loss of Excised-Leaves

A study was conducted with the objective of improvement of water use efficiency (WUE) and yield of winter wheat for Lowland Dryland Farming systems through a breeding approach. Various genotypes were screened in 1988 for rate of water loss of excised leaves (RWL) , followed by inter-crossing of diverse parents in 1993. Analysis of the relationship between RWL and yield components and plant traits demonstrated significant differences in RWL among genotypes. Under most circumstances, RWL was correlated negatively with yield and grain weight, and positively with plant height. The results demonstrated a basis for simultaneous selection for high yield and low RWL. It was found that genotypic rank varied with the duration of water loss. Correlation between RWL and yield was reduced by extended water loss duration. Analysis of the genetic variation and segregation of RWL of progenies and the effect of simultaneous screening for RWL and agronomic traits showed that good lines with improved yield and water use performance could be obtained.

The Impact of Discount Rate and Price on Intertemporal Groundwater Models in Southwest Kansas

Agriculture plays a vital role in the growth and development of the High Plains Region of the United States. With the development and adoption of irrigation technology, this region was transformed into one of the most agriculturally productive regions in the world [1]. The primary source of irrigation in this region is the Ogallala Aquifer. Currently, water from the aquifer is being used at a much faster rate than natural recharge can occur, resulting in a high rate of depletion from this finite resource. Depletion of scarce water resources will have a significant economic impact on the long-term sustainability of the region. The objective of this study is to evaluate the impact alternative prices and discount rates have on groundwater policy recommendations. Deterministic models of groundwater withdrawals were developed and used in order to analyze and evaluate the impact of high, average, and low crop prices in a status quo scenario as well as a policy scenario reducing irrigated acreage allocation. Furthermore, this study analyzes the effects and associated consequences of alternative discount rates on net and total revenue. As indicated by results of this study, alternative prices, costs, and discount rates utilized in a model have an effect on policy effectiveness.

Variable Chlorine Decay Rate Modeling of the Matsapha Town Water Network Using EPANET Program

A variable chlorine decay rate modeling of the Matsapha town water network was developed based on initial chlorine dosages. The model was adequately described by a second order rate function of the chlorine decay rate with respect to the initial chlorine dose applied. Simulations of chlorine residuals within the Matsapha water distribution network were run using the EPANET 2.0 program at different initial chlorine dosages and using the variable decay rate as described by the second order model. The measurement results indicated that the use of constant decay rate tended to underestimate chlorine residuals leading to potentially excess dosages with the associated chemical cost and side effects. The error between the two rate models varied between 0% and 15%. It is suggested that the use of water quality simulation programs such as EPANET be enhanced through the extension programs that accommodate variable rate modeling of chlorine residuals within distribution systems.