Adsorbed and free gas occurrence characteristics and controlling factors of deep shales in the southern Sichuan Basin,China

Deep shale gas(3500-4500 m)will be the important succeeding field for the growth of shale gas production in China.Under the condition of high temperature and high pressure in deep shale gas reservoirs,its gas occurrence characteristics are markedly different from those of medium and shallow layers.To elucidate the gas occurrence characteristics and controlling factors of deep shales in the Wufeng-Longmaxi Formation,methane adsorption,low-temperature N2,and cO2 adsorption experi-ments were conducted.The results show that in deep shales,the mesopores provide approximately 75%of the total specific surface area(SA)and 90%of the total pore volume(PV).Based on two hypotheses and comparing the theoretical and actual adsorption capacity,it is speculated that methane is adsorbed in deep shale in the form of micropore filling,and free gas is mainly stored in the mesopores.Correlation analysis demonstrated that ToC is the key material constraint for the adsorption capacity of deep shale,and micropore SSA is the key spatial constraint.Other minerals and mesopore parameters have limited effect on the amount of adsorbed gas.Moreover,the free gas content ranges from 2.72 m^(3)/t to 6.20 m^(3)/t,with an average value of 4.60 m^(3)/t,and the free gas content ratio is approximately 58%,suggesting that the deep shale gas reservoirs are dominated by free gas.This ratio may also increase to approximately 70%when considering the formation temperature effect on adsorbed gas.Gas density,porosity,and gas saturation are the main controlling factors of free gas content,resulting in significantly larger free gas content in deep shale than in shallower formations.

Characteristics of gaseous product from municipal solid waste gasification with hot blast furnace slag

Possibility of combustible gas production from municipal solid waste （MSW） using hot blast furnace （BF） slag has been studied.The objective of this work is to generate combustible gas from MSW using heated BF slag.In this experiment,the thermal stability of the MSW was analyzed by thermogravimetric analysis,and effects of temperature,gasifying agent （air,N2,steam） and BF slag on the gas products were investigated at 600？900 ？C.The thermogravimetric analysis indicates that the weight loss of MSW includes four stages：evaporation of the moisture,combustion of volatile materials,burning of carbon residue and burnout of ash.The contents of the combustible gas increase with increasing temperature,and the lower calorific value （LCV） increases rapidly at 600？900 ？C.It is found that volume fraction of CO,H2 and CH4 at different atmospheres increases in the order N2〈air〈steam.It is believed that BF slag acts as the catalyst and the heat carrier,which promotes the gasification reactivity of MSW.

Distribution Characteristics and Accumulation Model for the Coal-formed Gas Generated from Permo-Carboniferous Coal Measures in Bohai Bay Basin, China: A Review

Coal-formed gas generated from the Permo-Carboniferous coal measures has become one of the most important targets for deep hydrocarbon exploration in the Bohai Bay Basin,offshore eastern China.However,the proven gas reserves from this source rock remain low to date,and the distribution characteristics and accumulation model for the coal-formed gas are not clear.Here we review the coal-formed gas deposits formed from the Permo-Carboniferous coal measures in the Bohai Bay Basin.The accumulations are scattered,and dominated by middle-small sized gas fields,of which the proven reserves ranging from 0.002 to 149.4×108 m3 with an average of 44.30×108 m3 and a mid-point of 8.16×108 m3.The commercially valuable gas fields are mainly found in the central and southern parts of the basin.Vertically,the coal-formed gas is accumulated at multiple stratigraphic levels from Paleogene to Archaeozoic,among which the Paleogene and PermoCarboniferous are the main reservoir strata.According to the transporting pathway,filling mechanism and the relationship between source rocks and reservoir,the coal-formed gas accumulation model can be defined into three types:"Upward migrated,fault transported gas"accumulation model,"Laterally migrated,sandbody transported gas"accumulation model,and"Downward migrated,sub-source,fracture transported gas"accumulation model.Source rock distribution,thermal evolution and hydrocarbon generation capacity are the fundamental controlling factors for the macro distribution and enrichment of the coal-formed gas.The fault activity and the configuration of fault and caprock control the vertical enrichment pattern.

Migration and accumulation characteristics of natural gas hydrates in the uplifts and their slope zones in the Qiongdongnan Basin,China

Various factors controlling the accumulation of natural gas hydrates(NGHs)form various enrichment and accumulation modes through organic combination.This study mainly analyzes the geological and geophysical characteristics of the NGHs occurrence in the uplifts and their slope zones within the deep-water area in the Qiongdongnan(QDN)Basin(also referred to as the study area).Furthermore,it investigates the dominant governing factors and models of NGHs migration and accumulation in the study area.The results are as follows.(1)The uplifts and their slope zones in the study area lie in the dominant pressure-relief direction of fluids in central hydrocarbon-rich sags in the area,which provide sufficient gas sources for the NGHs accumulation and enrichment through pathways such as gas chimneys and faults.(2)The top and flanks of gas chimneys below the bottom simulating reflectors(BSRs)show high-amplitude seismic reflections and pronounced transverse charging of free gas,indicating the occurrence of a large amount of gas accumulation at the heights of the uplifts.(3)Chimneys,faults,and high-porosity and high-permeability strata,which connect the gas hydrate temperature-pressure stability zones(GHSZs)with thermogenic gas and biogenic gas,form the main hydrate migration system.(4)The reservoir system in the study area comprises sedimentary interlayers consisting of mass transport deposits(MTDs)and turbidites.In addition,the reservoir system has developed fissure-and pore-filling types of hydrates in the pathways.The above well-matched controlling factors of hydrate accumulation enable the uplifts and their slope zones in the study area to become the favorable targets of NGHs exploration.

Upper Paleozoic total petroleum system and geological model of natural gas enrichment in Ordos Basin, NW China

Based on the analysis of Upper Paleozoic source rocks, source-reservoir-caprock assemblage, and gas accumulation characteristics in the Ordos Basin, the gas accumulation geological model of total petroleum system is determined. Then, taking the Carboniferous Benxi Formation and the Permian Taiyuan Formation and Shanxi Formation as examples, the main controlling factors of gas accumulation and enrichment are discussed, and the gas enrichment models of total petroleum system are established. The results show that the source rocks, faults and tight reservoirs and their mutual coupling relations control the distribution and enrichment of gas. Specifically, the distribution and hydrocarbon generation capacity of source rocks control the enrichment degree and distribution range of retained shale gas and tight gas in the source. The coupling between the hydrocarbon generation capacity of source rocks and the physical properties of tight reservoirs controls the distribution and sweet spot development of near-source tight gas in the basin center. The far-source tight gas in the basin margin is mainly controlled by the distribution of faults, and the distribution of inner-source, near-source and far-source gas is adjusted and reformed by faults. Generally, the Upper Paleozoic gas in the Ordos Basin is recognized in four enrichment models: inner-source coalbed gas and shale gas, inner-source tight sandstone gas, near-source tight gas, and far-source fault-transported gas. In the Ordos Basin, inner-source tight gas and near-source tight gas are the current focuses of exploration, and inner-source coalbed gas and shale gas and far-source gas will be important potential targets in the future.

INFLUENCE OF Pr_6O_(11) ON THE GAS SENSING CHARACTERISTICS OF SnO_2 SEMICONDUCTOR

This paper is to discuss the sensing characteristics of SnO_2 semiconductor components in which Pr_6O_(11) is added.When experimenting under 11 gases of CH_3COCH_3,C_2H_5OH.C_6H_5CH_3,H_2,NH_3,CO, CO_2 CH_4,C_4H_10,n—C_6H_(14)and n—C_7H_(16),we find that the components have selectivity to CH_3COCH_3, C_2H_5OH and that the ideal amount of Pr_6O_(11) in the components is about I.Owt%.The experiments also show that with the increase of the amount of Pr_6O_(11),the ideal working temperature,the response and restoration time decrease.

Adsorption Regularity and Characteristics of sp^3-Hybridized Gas Molecules on Anatase TiO_2(101) Surface

We report the anatase titanium dioxide （101） surface adsorption of sp3-hybridized gas molecules, including NH3, 1-12 0 and CH4, using first-principles plane-wave ultrasoft pseudopotential based on the density functional theory. The results show that it is much easier for a surface with oxygen vacancies to adsorb gas molecules than it is for a surface without oxygen vacancies. The main factor affecting adsorption stability and energy is the polarizability of molecules, and adsorption is induced by surface oxygen vacancies of the negatively charged center. The analyses of state densities and charge population show that charge transfer occurs at the molecule surface upon adsorption and that the number of transferred charge reduces in the order of N, 0 and C. Moreover, the adsorption method is chemical adsorption, and adsorption stability decreases in the order of NH3, tt2 0 and CH4. Analyses of absorption and reflectance spectra reveal that after absorbed CH4 and H2 O, compared with the surface with oxygen vacancy, the optical properties of materials surface, including its absorption coefficients and reflectivity index, have slight changes, however, absorption coefficient and reflectivity would greatly increase after NH3 adsorption. These findings illustrate that anatase titanium dioxide （101） surface is extremely sensitive to NH3.

Control Factors and Diversities of Phase State of Oil and Gas Pools in the Kuqa Petroleum System

Based on the analysis of the hydrocarbon geochemical characteristics in the Kuqa petroleum system of the Tarim Basin, this study discusses the causes and controlling factors of the phase diversities and their differences in geochemical features. According to the characteristics and differences in oil and gas phase, the petroleum system can be divided into five categories： oil reservoir, wet gas reservoir, condensate gas-rich reservoir, condensate gas-poor reservoir and dry gas reservoir. The causes for the diversities in oil and gas phases include diversities of the sources of parent material, maturity of natural gas and the process of hydrocarbon accumulation of different hydrocarbon phases. On the whole, the Jurassic and Triassic terrestrial source rocks are the main sources for the hydrocarbon in the Kuqa Depression. The small differences in parent material may cause diversities in oil and gas amount, but the impact is small. The differences in oil and gas phase are mainly affected by maturity and the accumulation process, which closely relates with each other. Oil and gas at different thermal evolution stage can be captured in different accumulation process.

Characteristics and development model of karst reservoirs in the fourth member of Sinian Dengying Formation in central Sichuan Basin,SW China

The reservoir space,types and distribution characteristics of karst carbonate gas reservoirs in the fourth member of Sinian Dengying Formation(Deng 4 Member)in central Sichuan Basin are analyzed based on the drilling,logging and seismic data.A development model of karst reservoirs is constructed to support the high-efficiency development of gas pools.The research shows that the reservoirs in Deng 4 Member have mainly small-scale karst vugs and fractures as storage space,and can be divided into three types,fracture-vug,pore-vug and pore types.The development patterns of the karst reservoirs are determined.On the plane,the karst layers increase from 65 m to 170 m in thickness from the karst platform to the karst slope,and the high-quality reservoirs increase from 25.0 m to 42.2 m in thickness;vertically,the reservoirs at the top of Deng 4 Member appear in multiple layers,and show along-bedding and along fracture dissolution characteristics.The reservoirs at the bottom are characterized by the dissolution parallel to the water level during the karstification period,and have 3-5 large-scale fracture-cave systems.Based on the reservoir development characteristics and the genetic mechanism,three types of reservoir development models of karst reservoir are established,i.e.,bed-dissolved body,fracture-dissolved body and paleohorizon-dissolved body.The construction of karst reservoir development models and seismic response characteristics of the three types of reservoirs can provide parameter for well placement and trajectory design,and substantially improve productivity and development indices of individual wells and gas reservoirs.The designed production capacity of the gas reservoir has enhanced from the initial 3.6 billion to 6 billion cubic meters,making the profit of the reservoir development increase noticeably.

The effective ionization coefficients and electron drift velocities in gas mixtures of CF_3I with N_2 and CO_2 obtained from Boltzmann equation analysis

The electron swarm parameters including the density-normalized effective ionization coefficients（α-η）/N and the electron drift velocities V e are calculated for a gas mixture of CF3I with N2 and CO2 by solving the Boltzmann equation in the condition of a steady-state Townsend（SST） experiment.The overall density-reduced electric field strength is from 100 Td to 1000 Td（1 Td = 10-17V·cm2）,while the CF3I content k in the gas mixture can be varied over the range from 0% to 100%.From the variation of（αη）/N with the CF3I mixture ratio k,the limiting field strength（E/N） lim for each CF3I concentration is derived.It is found that for the mixtures with 70% CF3I,the values of（E/N） lim are essentially the same as that for pure SF 6.Additionally,the global warming potential（GWP） and the liquefaction temperature of the gas mixtures are also taken into account to evaluate the possibility of application in the gas insulation of power equipment.

Restoration of Eroded Thickness of the Neogene Strata in the Western Qaidam Basin and Its Significance for Oil and Gas Occurrence

During the Pleistocene, the western Qaidam Basin has largely experienced strong structural reconstruction and strong erosion. First, the eroded thickness of Neogene strata was restored approximately by the stratigraphic profile comparison method and plane trend surface restoring method; then, accurate calculation of erosion was recovered using vitrinite reflectance, and the erosion that was restored by the trend surface restoring method was corrected; finally, a distribution map of cumulative erosion was produced. This study marks an important achievement in that one of the most important parameters of basin tectonic evolution, sedimentary evolution, and oil and gas accumulation history has been obtained, and that a basic geological problem has been solved in the Qaidam Basin. The areas with high erosion and low erosion are shown in the map and a close relation between the distribution of oil and gas fields and erosion was recognized. Large and medium oil and gas fields are mainly distributed in areas with medium and low erosion. It is difficult to form large-scale oil and gas accumulation in areas in which erosion is more than 2000 m. The mechanism of the relation between oil and gas distribution and erosion is explained. This study will be of use in predicting the distribution of oil and gas.

Microscopic pore-fracture configuration and gas-filled mechanism of shale reservoirs in the western Chongqing area,Sichuan Basin,China

Taking the Upper Ordovician Wufeng Formation to Lower Silurian Longmaxi Formation shale reservoirs in western Chongqing area as the study target,the argon ion polishing scanning electron microscope and nuclear magnetic resonance(NMR)experiments of different saturated wetting media were carried out.Based on the image processing technology and the results of gas desorption,the pore-fracture configuration of the shale reservoirs and its influence on gas-filled mechanism were analyzed.(1)The reservoir space includes organic pores,inorganic pores and micro-fractures and there are obvious differences between wells in the development characteristics of micro-fractures;the organic pores adjacent to the micro-fractures are poorly developed,while the inorganic pores are well preserved.(2)According to the type,development degree and contact relationship of organic pore and micro-fracture,the pore-fracture configuration of the shale reservoir is divided into four types.(3)Based on the differences in NMR T_(2) spectra of shale samples saturated with oil and water,an evaluation parameter of pore-fracture configuration was constructed and calculated.The smaller the parameter,the better the pore-fracture configuration is.(4)The shale reservoir with good pore-fracture configuration has well-developed organic pores,high porosity,high permeability and high gas content,while the shale reservoir with poor pore-fracture configuration has micro-fractures developed,which improves the natural gas conductivity and leads to low porosity and gas content of the reservoir.(5)Based on pore-fracture configuration,from the perspective of organic matter generating hydrocarbon,micro-fracture providing migration channel,three types of micro gas-filled models of shale gas were established.

Gas release characteristics during carbonization of iron coke hot briquette and influence of heating rate

The release characteristics of CH_(4),H_(2),CO and CO_(2) from iron coke hot briquette(ICHB)during carbonization were studied.The results show that compared with briquette without iron ore,Fe_(3)O_(4) can inhibit the release rate of H2 and promote the production of CO and CO_(2).In addition,when the heating rate increases from 3 to 7℃/min,the release rates of CH4 and H2 increase,while the release rates of CO and CO_(2) first increase and then decrease.The carbonization process of ICHB was segmented,and corresponding kinetic analysis was carried out.The results show that the activation energy of StageⅡand StageⅣis higher in the carbonization process of ICHB,and the active pyrolysis of coal and the reduction of iron ore occur in these two stages.In addition,the effect of heating rate on the kinetic parameters of ICHB carbonization process was investigated.It was found that when the heating rate increased,the reaction activation energy of StageⅣdecreased first and then increased,which was consistent with the release law of CO and CO_(2).The analysis showed that the increase in heating rate leads to more reactions at higher temperatures,resulting in an increase in the release rate of some gases.In addition,thermal hysteresis can also cause some processes to fail to fully react at the end of heating.It is also found that the apparent activation energy and preexponential factor have kinetic compensation effect during the car-bonization of ICHB.

Numerical simulation on gas-solid flow during circulating fluidized roasting of bauxite by a computational particle fluid dynamics method

A full-cycle numerical simulation of a circulating fluidized bed(CFB)by the use of the computational particle fluid dynamics(CPFD)method has been developed.The effects of the presence or absence of the secondary air,different secondary air positions,and different secondary air ratios on the gas–solid flow characteristics were explored.The results show that the presence of the secondary air makes a core-annular structure of the velocity distribution of particles in the fluidized bed,which enhances the uniformity of particles’distribution and the stability of fluidization.The position and the ratio of the secondary air have a significant impact on the particle distribution,particle flow rate,and gas flow rate in the fluidized bed.When the secondary air position and ratio are optimal,the particles,particle flow rate,and air flow rate in the CFB are evenly distributed,the gas–solid flow state is good,and the CFB can operate stably.

Computational fluid dynamic modeling of gas flow characteristics of the high-power CW CO_2 laser

To increase the photoelectronic conversion efficiency of the single discharge tube and to meet the requirements of the laser cutting system, optimization of the discharge tube structure and gas flow field is necessary. We present a computational fluid dynamic model to predict the gas flow characteristics of high-power fast-axial flow CO2 laser. A set of differential equations is used to describe the operation of the laser. Gas flow characteristics, are calculated. The effects of gas velocity and turbulence intensity on discharge stability are studied. Computational results are compared with experimental values, and a good agreement is observed. The method presented and the results obtained can make the design process more efficient.

Effect of methane-hydrogen mixtures on flow and combustion of coherent jets

Coherent jets are widely used in electric are furnace （EAF） steelmaking to increase the oxygen utilization and chemical reaction rates. However, the influence of fuel gas combustion on jet behavior is not fully understood yet. The flow and combustion characteristics of a coherent jet were thus investigated at steelmaking temperature using Fluent software, and a detailed chemical kinetic reaction mecha- nism was used in the combustion reaction model. The axial velocity and total temperature of the supersonic jet were measured via hot state experiments. The simulation results were compared with the experimental data and the empirical jet model proposed by Ito and Muchi and good consistency was obtained. The research results indicated that the potential core length of the coherent jet can be prolonged by optimizing the combustion effect of the fuel gas. Besides, the behavior of the supersonic jet in the subsonic section was also investigated, as it is an important factor for controlling the position of the oxygen lance. The investigation indicated that the attenuation of the coherent jet is more notable than that of the conventional jet in the subsonic section.