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.

Rock mass response for lined rock caverns subjected to high internal gas pressure

The storage of hydrogen gas in underground lined rock caverns(LRCs)enables the implementation of the first fossil-free steelmaking process to meet the large demand for crude steel.Predicting the response of rock mass is important to ensure that gas leakage due to rupture of the steel lining does not occur.Analytical and numerical models can be used to estimate the rock mass response to high internal pressure;however,the fitness of these models under different in situ stress conditions and cavern shapes has not been studied.In this paper,the suitability of analytical and numerical models to estimate the maximum cavern wall tangential strain under high internal pressure is studied.The analytical model is derived in detail and finite element(FE)models considering both two-dimensional(2D)and three-dimensional(3D)geometries are presented.These models are verified with field measurements from the LRC in Skallen,southwestern Sweden.The analytical model is inexpensive to implement and gives good results for isotropic in situ stress conditions and large cavern heights.For the case of anisotropic horizontal in situ stresses,as the conditions in Skallen,the 3D FE model is the best approach.

Conversion of producer gas using NiO/SBA-15 obtained with different synthesis methods

In this study,NiO/SBA-15 was prepared by both direct and post synthesis methods.TEM images revealed that NiO particles aggregated in NiO/SBA-15 obtained with post synthesis method,regardless of NiO loading.However,NiO particles were monodispersed in NiO/SBA-15 with a NiO loading of less than 15 wt%by using the direct synthesis method.In this case,NiO particles aggregated when NiO loading was over 20 wt%.TPR analysis verified that with direct synthesis method the location boundary of NiO particles on outer and pore surface could be observed clearly,whereas that could not observed in the case of post synthesis method.This indicates that the type of synthesis method displays significant effect on the location of NiO particles dispersed into the SBA-15.Producer gas conversion was carried out using NiO/SBA-15 as catalysts,which were synthesized with different synthesis methods.The gas conversion including methanation occurred at low temperature(i.e.,300-400℃)and the reverse water gas shift(RWGS)reaction at hightemperature(i.e.,400-900℃).High temperatures facilitated CO conversion to CO with CO selectivity close to 100%,regardless of the synthesis method of the used catalyst.At low temperatures the dispersion type of NiO particles affectedthe CO,conversion reaction,i.e.,monodispersed Ni0 particles gave a CO selectivity of close to 100%,similar to thatobtained at high temperature.The aggregated NiO particles resuled in a CO selectivity of less than 100%owing to CH,formation,regardless of synthesis method of catalyst.Therefore,NiO/SBA-15 obtained with direct synthesis methodfavored RWGS reaction because of high CO selectivity.NiOSBA-15 obtained with post synthesis method is suited formethanation because of high CH selectivity,and the conversion of CO,to CHa through methanation increased withincreasing NiO loading.

Dissimilar welding of high nitrogen stainless steel and low alloy high strength steel under different shielding gas composition:Process,microstructure and mechanical properties

Ar-N_(2)-O_(2)ternary shielding gas is employed in dissimilar welding between high nitrogen steel and low alloy steel.The effect of O_(2)and N_(2)is investigated based on the systematical analysis of the metal transfer,nitrogen escape phenomenon,weld appearance,nondestructive detection,nitrogen content distribution,microstructure and mechanical properties.There are two nitrogen sources of the nitrogen in the weld:high nitrogen base material and shielding gas.The effect of shielding gas is mainly reflected in these two aspects.The change of the droplet transfer mode affects the fusion ratio,N2in the shielding gas can increase nitrogen content and promote the nitrogen uniform distribution.The addition of 2%O_(2)to Ar matrix can change the metal transfer from globular transfer to spray transfer,high nitrogen base material is thereby dissolved more to the molten pool,making nitrogen content increase,ferrite decrease and the mechanical properties improve.When applying N2-containing shielding gas,arc stability becomes poor and short-circuiting transfer frequency increases due to the nitrogen escape from droplets and the molten pool.Performance of the joints is improved with N_(2)increasing,but internal gas pores are easier to appear because of the poor capacity of low alloy steel to dissolve nitrogen,The generation of pores will greatly reduce the impact resistance.4-8%N2content in shielding gas is recommended in this study considering the integrated properties of the dissimilar welded joint.

Geological characteristics and high production control factors of shale gas reservoirs in Silurian Longmaxi Formation, southern Sichuan Basin, SW China

Marine shale gas resources have great potential in the south of the Sichuan Basin in China.At present,the high-quality shale gas resources at depth of 2000–3500 m are under effective development,and strategic breakthroughs have been made in deeper shale gas resources at depth of 3500–4500 m.To promote the effective production of shale gas in this area,this study examines key factors controlling high shale gas production and presents the next exploration direction in the southern Sichuan Basin based on summarizing the geological understandings from the Lower Silurian Longmaxi Formation shale gas exploration combined with the latest results of geological evaluation.The results show that:(1)The relative sea depth in marine shelf sedimentary environment controls the development and distribution of reservoirs.In the relatively deep water area in deep-water shelf,grade-I reservoirs with a larger continuous thickness develop.The relative depth of sea in marine shelf sedimentary environment can be determined by redox conditions.The research shows that the uranium to thorium mass ratio greater than 1.25 indicates relatively deep water in anoxic reduction environment,and the uranium to thorium mass ratio of 0.75–1.25 indicates semi-deep water in weak reduction and weak oxidation environment,and the uranium to thorium mass ratio less than 0.75 indicates relatively shallow water in strong oxidation environment.(2)The propped fractures in shale reservoirs subject to fracturing treatment are generally 10–12 m high,if grade-I reservoirs are more than 10 m in continuous thickness,then all the propped section would be high-quality reserves;in this case,the longer the continuous thickness of penetrated grade-I reservoirs,the higher the production will be.(3)The shale gas reservoirs at 3500–4500 m depth in southern Sichuan are characterized by high formation pressure,high pressure coefficient,well preserved pores,good pore structure and high proportion of free gas,making them the most favorable new field for shale gas exploration;and the pressure coefficient greater than 1.2 is a necessary condition for shale gas wells to obtain high production.(4)High production wells in the deep shale gas reservoirs are those in areas where Long11-Long13 sub-beds are more than 10 m thick,with 1500 m long horizontal section,grade-I reservoirs penetration rate of over 90%,and fractured by dense cutting+high intensity sand injection+large displacement+large liquid volume.(5)The relatively deep-water area in the deep-water shelf and the area at depth of 3500–4500 m well overlap in the southern Sichuan,and the overlapping area is the most favorable shale gas exploration and development zones in the southern Sichuan in the future.With advancement in theory and technology,annual shale gas production in the southern Sichuan is expected to reach 450×108 m3.

Effect of rock joints on lined rock caverns subjected to high internal gaspressure

The storage of hydrogen gas in lined rock caverns(LRCs)may enable the implementation of the firstlarge-scale fossil-free steelmaking process in Sweden,but filling such storage causes joints in the rockmass to open,concentrating strains in the lining.The structural interaction between the LRC componentsmust be able to reduce the strain concentration in the sealing steel lining;however,this interaction iscomplex and difficult to predict with analytical methods.In this paper,the strain concentration in LRCsfrom the opening of rock joints is studied using finite element(FE)analyses,where the large-and small-scale deformation behaviors of the LRC are coupled.The model also includes concrete crack initiation anddevelopment with increasing gas pressure and rock joint width.The interaction between the jointed rockmass and the reinforced concrete,the sliding layer,and the steel lining is demonstrated.The results showthat the rock mass quality and the spacing of the rock joints have the greatest influence on the straindistributions in the steel lining.The largest effect of rock joints on the maximum strains in the steellining was observed for geological conditions of“good”quality rock masses.

Performance evaluation of a diesel engine by using producer gas from some under-utilized biomass on dual-fuel mode of diesel cum producer gas

Producer gas through gasification of biomass can be used as an alternate fuel in rural areas due to high potential of biomass resources in India.Experiments were conducted to study the performance of a diesel engine(four stroke,single cylinder,5.25 kW) with respect to its thermal efficiency,specific fuel consumption and diesel substitution by use of diesel alone and producer gas-cum-diesel(dual fuel mode).Three types of biomass,i.e.wood chips,pigeon pea stalks and corn cobs were used for generation of producer gas.A producer gas system consisting of a downdraft gasifier,a cooling cum cleaning unit,a filtering unit and a gas air mixing device was designed,fabricated and used to power a 5.25 kW diesel engine on dual fuel mode.Performance of the engine was reported by keeping biomass moisture contents as 8%,12%,16%,and 21%,engine speed as 1 600 r/min and with variable engine loads.The average value of thermal efficiency on dual fuel mode was found slightly lower than that of diesel mode.The specific diesel consumption was found to be 60%-64% less in dual fuel mode than that in diesel mode for the same amount of energy output.The average diesel substitution of 74% was observed with wood chips followed by corn cobs(78%) and pigeon pea stalks(82%).Based on the performance studied,the producer gas may be used as a substitute or as supplementary fuel for diesel conservation,particularly for stationary engines in agricultural operations in the farm.

Effects of instantaneous shut-in of high production gas well on fluid flow in tubing

As the classical transient flow model cannot simulate the water hammer effect of gas well, a transient flow mathematical model of multiphase flow gas well is established based on the mechanism of water hammer effect and the theory of multiphase flow. With this model, the transient flow of gas well can be simulated by segmenting the curved part of tubing and calculating numerical solution with the method of characteristic curve. The results show that the higher the opening coefficient of the valve when closed, the larger the peak value of the wellhead pressure, the more gentle the pressure fluctuation, and the less obvious the pressure mutation area will be. On the premise of not exceeding the maximum shut-in pressure of the tubing, adopting large opening coefficient can reduce the impact of the pressure wave. The higher the cross-section liquid holdup, the greater the pressure wave speed, and the shorter the propagation period will be. The larger the liquid holdup, the larger the variation range of pressure, and the greater the pressure will be. In actual production, the production parameters can be adjusted to get the appropriate liquid holdup, control the magnitude and range of fluctuation pressure, and reduce the impact of water hammer effect. When the valve closing time increases, the maximum fluctuating pressure value of the wellhead decreases, the time of pressure peak delays, and the pressure mutation area gradually disappears. The shorter the valve closing time, the faster the pressure wave propagates. Case simulation proves that the transient flow model of gas well can optimize the reasonable valve opening coefficient and valve closing time, reduce the harm of water hammer impact on the wellhead device and tubing, and ensure the integrity of the wellbore.

Mechanochemical Methods in the Production of High Purity Gases

The development of advanced and cost-effective methods is of prime importance for manufacturers of high purity gases. In this paper a new strategy in the development of gas flow purification technologies is described, where instead of adsorbents reactants are used, in which not only the surface is used in gas capturing but the entire volume of the material. Moreover, the reactants are activated in the gas flow by a controlled mechanical tool, which keeps the sorption kinetics at the required highest level and reduces the unproductive losses of the consumed reactant almost to zero. The advantages of the method are demonstrated with the examples of two novel gas purification units that are distinguished with uncomplicated design, serviceability and ultimately high purification efficiency.

Shale high pressure isothermal adsorption curve and the production dynamic experiments of gas well

The high pressure static adsorption curves of shale samples from Silurian Changning-Weiyuan Longmaxi Formation were tested by using high pressure isothermal adsorption equipment.The physical modeling of depletion production was tested on single cores and multi-core series by using self-developed shale gas fluid-solid coupling experiment system.The adsorption and desorption laws were summarized and a high pressure isothermal adsorption model was established.The calculation formula of gas content was corrected,and the producing law of adsorption gas was determined.The study results show that the isothermal adsorption law of the shale reservoir under high pressure was different from the conventional low pressure.The high pressure isothermal adsorption curve had the maximum value in excess adsorption with pressure change,and the corresponding pressure was the critical desorption pressure.The high pressure isothermal curve can be used to evaluate the amount of adsorbed gas and the producing degree of adsorption gas.The high pressure isothermal adsorption model can fit and characterize the high pressure isothermal adsorption law of shale.The modified gas content calculation method can evaluate the gas content and the proportion of adsorbed gas more objectively,and is the theoretical basis of reserve assessment and production decline analysis.The producing degree of adsorption gas is closely related to the pressure,only when the reservoir pressure is lower than the critical desorption pressure,the adsorption gas can be produced effectively.In the process of gas well production,the pressure drop in the near-well area is large,the production of adsorption gas is high;away from the wellbore,the adsorption gas is low in production,or no production.

Purification of Produced Water from a Sour Oilfield in South Kuwait. 1. Oil-Water Separation and Industrial Salt Production

Produced water from an oil extraction site in South Kuwait was sampled after primary oil – water separation had been carried out. The produced water was filtered through a mixture of activated charcoal and esterified cellulosic material gained from spent coffee grounds as a tertiary adsorption treatment. The earth-alkaline metal ions and heavy metals were separated from the de-oiled produced water by addition of either sodium or potassium hydroxide in the presence of carbon dioxide or by direct addition of solid sodium carbonate. The resulting filtrate gave salt of industrial purity upon selective crystallization on evaporation.

Purification of Produced Water from a Sour Oilfield in South Kuwait. 2. Oil-Water Separation and Crystallization of Calcium Carbonate

Oil-water separation for produced water (PW) originating from an oil extraction site in South Kuwait was carried out using bleached, esterified cellulosic material from used coffee grounds. Thereafter, earth-alkaline metal ions, specifically calcium ions, of the de-oiled PW were removed by precipitation with sodium carbonate to give access to pure sodium chloride as industrial salt from the remaining PW. While the purity of the precipitated calcium carbonate (CaCO3) depends on the precipitation conditions, CaCO3 of up to 95.48% purity can be obtained, which makes it a salable product. The precipitation of CaCO3 decreases the amount of calcium ions in PW from 11,300 ppm to 84 ppm.

Time Characterization of High Density Gas Jet from a Pulsed Supersonic Nozzle via Laser Produced Plasma

A high-density gas jet supersonic nozzle is reported in this paper. The jitter and actuation time of the nozzle is determined by the pin discharge and laser spark radiation respectively. The jitter time of the nozzle is within 10μs with the backing pressure as high as 25 bar. With a nanosecond laser pulse focused on the gas jet about 1 mm below the nozzle, the actuation time is calculated to be about 15 ms by detecting the laser produced spark radiation, which reveals the existence of the gas jet and the relative gas density evolving with time. Consequently the gas density is estimated to be well above 10^19 cm^-3, compared with theoretical simulations from the nozzle parameters.

Xinjiang to Become China's Largest Natural Gas Producer

With the opening of the Kela No. 2 gas field in the Tarim basin in China’s northwest Xinjiang Uygur Autonomous Region on Dec. 1, Xinjiang will produce 10 billion cubic meters of natural gas next year, becoming the country’s largest gas producer, according to an official with the China National Petroleum Corporation.

Classification of Chinese Traditional Drug-"Beimu" (Bulbus Fritillariae) by Pyrolysis High Resolution Gas Chromatography-Pattern Recognition

The combination of pyrolysis high resolution gas chromatography and pat- tern recognition techniques is a powerful tool for the classification of traditional Chinese drug.A study has been completed on 55 Beimu samples of five different geographic origins: Eastern China.Central China.South-western China,North-western China and North-eastern China.Principal component analysis and SIMCA are applied to effectively classifying the samples according to the origin of the plants.The chemical information contained in the high resolution gas chromatographic data is sufficient to characterize the geographic origin of sam- pies.

High in vitro survival rate of sheep in vitro produced blastocysts vitrified with a new method and device

Background:To advance the use of embryo vitrification in veterinary practice,we developed a system in which embryo vitrification,warming and dilution can be performed within a straw.Ovine in vitro produced embryos(IVEP)were vitrified at either early(EBs:n=74)or fully expanded blastocyst stage(FEBs:n=195),using a new device named"E.Vit",composed by a 0.25-m L straw with a 50-μm pore polycarbonate grid at one end.Embryos at each stage(EBs and FEBs)were vitrified by either Two-step(TS)or Multi-step(MS;6 different concentrations of vitrification solutions)protocol.Non-vitrified embryos(n=102)were maintained in in vitro culture as a control.Warming consisted of placing the straws directly into 1.5 m L tubes containing a TCM-199 solution with three decreasing concentrations of sucrose.Blastocyst re-expansion,embryo survival and hatching rate were evaluated at2,24 and 48 h post warming.The number of apoptotic cells was determined by TUNEL assay.Results:Blastocyst re-expansion(2 h)after warming was higher(P<0.05)in FEBs group,vitrified with the MS and TS methods(77.90%and 71.25%,respectively)compared with the EBs group(MS:59.38%and TS:48.50%,respectively).Survival rates of vitrified FEBs after 24 h IVC were higher(P<0.001)in both methods(MS and TS)than vitrified EBs(MS:56.25%;TS:42.42%)and was higher(P<0.05)in the MS method(94.19%)compared with those in TS(83.75%).After 48 h of culture the hatching rate for FEBs vitrified in MS system(91.86%)was similar to control(91.89%),but higher than FEB TS(77.5%)and EBs vitrified in MS(37.5%)and TS(33.33%).Number of apoptotic cells were higher in EBs,irrespective of the system used,compared to FEBs.The number of apoptotic cells in FEBs vitrified with MS was comparable to the control.Conclusions:A high survival rate of IVP embryos can be achieved by the new"E.Vit"device with hatching rates in vitro comparable with control fresh embryos.This method has the potential for use in direct embryo transfer in field conditions.

Applications of high-gravity technologies in gas purifications: A review

The traditional gas purification techniques such as wet gas desulfurization, with their advantages of large-scale implementation and maturity, have still been widely used. However, the main drawback of these techniques is the low transfer efficiency, which normally needs towers as tall as tens of meters to remove the pollutants. Therefore, new technologies which could enhance the mass transfer efficiency and are less energy-intensive are highly desirable. As a process intensification technology, high-gravity technology, which is carried out in a rotating packed bed(RPB), has recently demonstrated great potential for industrial applications due to its high mass transfer efficiency, energy-saving, and smaller volume. This consequently provides higher efficiency in toxic gas removal, and can significantly reduce the investment and operation costs. In this review, the mechanism,characteristics, recent developments, and the industry applications of high-gravity technologies in gas purifications, such as hydrogen sulfide, nitrogen oxide, carbon dioxide, sulfur dioxide, volatile organic compounds and nanoparticle removal are discussed, most of the demonstration projects and practical application examples in gas purification come from China. The perspective and prospective of this technology in gas purification and other fields are also briefly discussed.

Simulation of mold filling and prediction of gas entrapment on practical high pressure die castings

Element parameters including volume filled ratio,surface dimensionless distance,and surface filled ratio for DFDM(direct finite difference method)were proposed to describe shape and location of free surfaces in casting mold filling processes.A mathematical model of the filling process was proposed specially considering the mass,momentum and heat transfer in the vicinity of free surfaces.Furthermore,a method for gas entrapment was established by tracking flow of entrapped gas.The model and method were applied to practical ADC1 high pressure die castings.The gas entrapment prediction was compared with the fraction and maximum size of porosities in the different casting parts.The comparison shows validity of the proposed model and method.The study indicates that final porosities in high pressure die castings are dependent on both gas entrapment during mold filling process and pressure transfer within solidification period.

Microstructure evolution of Al_(0.6)CoCrFeNi high entropy alloy powder prepared by high pressure gas atomization

The influence of cooling rate on the microstructure of Al0.6CoCrFeNi high entropy alloy（HEA） powders was investigated. The spherical HEA powders（D50≈78.65 μm） were prepared by high pressure gas atomization. The different cooling rates were achieved by adjusting the powder diameter. Based on the solidification model, the relationship between the cooling rate and the powder diameter was developed. The FCC phase gradually disappears as particle size decreases. Further analysis reveals that the phase structure gradually changes from FCC＋BCC dual-phase to a single BCC phase with the increase of the cooling rate. The microstructure evolves from planar crystal to equiaxed grain with the cooling rate increasing from 3.19×10^4 to 1.11×10^6 K/s.

Origin and accumulation of high-maturity oil and gas in deep parts of the Baxian Depression, Bohai Bay Basin, China

Great quantities of light oil and gas are produced from deep buried hill reservoirs at depths of 5,641 m to 6,027 m and 190 ℃ to 201 ℃ in the Niudong-1 Well, representing the deepest and hottest commercial hydrocarbons discovered in the Bohai Bay Basin in eastern China. This discovery suggests favorable exploration prospects for the deep parts of the basin. However, the discovery raises questions regarding the genesis and accumulation of hydrocarbons in deep reservoirs. Based on the geochemical features of the hydrocarbons and characteristics of the source rocks as well as thermal simulation experiments of hydrocarbon generation, we conclude that the oil and gas were generated from the highly mature Sha-4 Member （Es4） source rocks instead of thermal cracking of crude oils in earlier accumulations. The source kitchen with abnormal pressures and karsted carbonate reservoirs control the formation of high-maturity hydrocarbon accumulations in the buried hills （i.e., Niudong-1） in conjunction with several structural-lithologic traps in the ES4 reservoirs since the deposition of the upper Minghuazhen Formation. This means the oil and gas exploration potential in the deep parts of the Baxian Depression is probably high.