Failure characteristics of surface vertical wells for relieved coal gas and their influencing factors in Huainan mining area

Based on data from through-hole and logging,we studied the failure characteristics of surface drainage wells for relieved coal gas in Huainan mining area and its influencing factors.The results show that the damaged positions of drainage wells are mainly located at the thick clay layer in the low alluvium and the lithological interface in the upper section of bedrock in west mining area.The failure depth of casing is 244-670 m and concentrates at about 270-460 m deep.These damaged positions are mainly located in the bending zone according to three zones of rock layers in the vertical section above the roof divided. Generally,the casing begins to deform or damage before the face line about 30-150 m.Special formation structure and rock mass properties are the direct causes of the casing failure,high mining height and fast advancing speed are fundamental reasons for rock mass damage.However,the borehole configuration and spacing to the casing failure are not very clear.

Methodological factors affecting gas and methane production during in vitro rumen fermentation evaluated by meta-analysis approach

Effects of some methodological factors on in vitro measures of gas production（GP, mL/g DM）, CH4production（mL/g DM） and proportion（% CH4 on total GP） were investigated by meta-analysis. These factors were considered：pressure in the GP equipment（0 = constant; 1 = increasing）, incubation time（0 = 24; 1 = ≥ 48 h）, time of rumen fluid collection（0 = before feeding; 1 = after feeding of donor animals）, donor species of rumen fluid（0 = sheep; 1 =bovine）, presence of N in the buffer solution（0 = presence; 1 = absence）, and ratio between amount of buffered rumen fluid and feed sample（BRF/FS; 0 = ≤ 130 mL/g DM; 1 = 130–140 mL/g DM; 2 = ≥ 140 mL/g DM）. The NDF content of feed sample incubated（NDF） was considered as a continuous variable. From an initial database of 105 papers, 58 were discarded because one of the above-mentioned factors was not stated. After discarding 17 papers,the final dataset comprised 30 papers（339 observations）. A preliminary mixed model analysis was carried out on experimental data considering the study as random factor. Variables adjusted for study effect were analyzed using a backward stepwise analysis including the above-mentioned variables. The analysis showed that the extension of incubation time and reduction of NDF increased GP and CH4 values. Values of GP and CH4 also increased when rumen fluid was collected after feeding compared to before feeding（＋26.4 and ＋9.0 mL/g DM, for GP and CH4）,from bovine compared to sheep（＋32.8 and ＋5.2 mL/g DM, for GP and CH4）, and when the buffer solution did not contain N（＋24.7 and ＋6.7 mL/g DM for GP and CH4）. The increase of BRF/FS ratio enhanced GP and CH4production（＋7.7 and ＋3.3 mL/g DM per each class of increase, respectively）. In vitro techniques for measuring GP and CH4 production are mostly used as screening methods, thus a full standardization of such techniques is not feasible. However, a greater harmonization of analytical procedures（i.e., a reduction in the number of available protocols） would be useful to facilitate comparison between results of different experiments.

2013 SCI Impact Factor being 1.788 for Journal of Natural Gas Chemistry

The SCI impact factor of Journal of Natural Gas Chemistry （JNGC） is 1.788, according to the ＂2013 Journal Citation Reports （JCR） Science Edition＂. This is the highest SCI impact factor for Journal of Natural Gas Chemistry since the journal was included in the Science Citation Index Expanded （SCIE） in 2007, and it ranks first among chemistry journals in China. Over the past decade, the Journal of Natural Gas Chemistry has become more and more international and has received large numbers of manuscripts concerning energy chemistry. In deed, nowadays enerzy chemistry is becoming one of the hot topics.

2011 SCI Impact Factor being 1.348 for Journal of Natural Gas Chemistry

The SCI impact factor of Journal of Natural Gas Chemistry （JNGC） is 1.348, according to the ＂2011 Journal Citation Reports （JCR） Science Edition＂. This is the highest SCI impact factor for Journal of Natural Gas Chemistry since the journal was included in the Science Citation Index Expanded （SCIE） in 2007, and it ranks first among chemistry journals in China.

Water coning mechanism in Tarim fractured sandstone gas reservoirs

The problem of water coning into the Tarim fractured sandstone gas reservoirs becomes one of the major concerns in terms of productivity, increased operating costs and environmental effects. Water coning is a phenomenon caused by the imbalance between gravity and viscous forces around the completion interval. There are several controllable and uncontrollable parameters influencing this problem. In order to simulate the key parameters affecting the water coning phenomenon, a model was developed to represent a single well with an underlying aquifer using the fractured sandstone gas reservoir data of the A-Well in Dina gas fields.The parametric study was performed by varying six properties individually over a representative range. The results show that matrix permeability, well penetration(especially fracture permeability), vertical-to-horizontal permeability ratio, aquifer size and gas production rate have considerable effect on water coning in the fractured gas reservoirs. Thus, investigation of the effective parameters is necessary to understand the mechanism of water coning phenomenon. Simulation of the problem helps to optimize the conditions in which the breakthrough of water coning is delayed.

Research on Calculation Method of Aerodynamic Parameters of Supersonic Probe Based on Gas Compressibility Factor

The supersonic multi-hole probe is an essential test tool for wind tunnel experiments, which is necessary to develop the basic research of improving the measurement accuracy and expanding the application of the probes.

Coupling effects of temperature,confining pressure,and pore pressure on permeability and average pore size of Longmaxi shale

The evolution due to temperature and pressure of shale reservoir permeability affects the productivity evaluation and development decision of shale gas reservoirs,which is very important for the exploration and development of unconventional gas reservoirs.This study analyzed the coupling effects of temperature(25,50,and 75°C),effective stress(15 and 30 MPa),and pore pressure(0.5,2.0,4.0,and 8.0 MPa)on the permeability of the shale sample in the Longmaxi Formation.As the temperature and pressure increased,the apparent permeability exhibited a downward trend,and the absolute permeability decreased with the rise of temperature or effective stress.An in‐depth analysis of the gas slippage factors under the conditions of different temperature and pressure was conducted to evaluate the trend of the average pore width with temperature and pressure.The results were then verified by scanning electron microscopy(SEM).The results provide new insights into evaluating the permeability of the Longmaxi shale and can be used to enhance the gas recovery rate of deep shale gas reservoirs.

Geological controls of shale gas accumulation and enrichment mechanism in Lower Cambrian Niutitang Formation of western Hubei, Middle Yangtze, China

The lower Cambrian Niutitang Formation is of crucial importance for shale gas target reservoirs in western Hubei,China;however,little work has been done in this field,and its shale gas accumulation and enrichment mechanism are still unclear.Based on survey wells,outcrop data,and large numbers of tests,the geological conditions of shale gas accumulation were studied;moreover,the factors that influence the gas content were thoroughly discussed.The results show that the Niutitang Formation(Є1n)can be divided into three sections:the first section(Є_(1)n^(1)),the second section(Є_(1)n^(2)),and the third section(Є1n3).TheЄ_(1)n^(2) is the main shale gas reservoir.The deep shelf facies is the main sedimentary facies and can be divided into three main lithofacies:argillaceous siltstone,carbonaceous shale and carbonaceous siliceous rock.The total organic carbon(TOC)content shows gentle growth trends until bottom of theЄ_(1)n^(2) and then decreases rapidly within theЄ_(1)n^(1),and the TOC content mainly ranges from 2%to 4%horizontally.The calcite and dolomite dissolution pores,clay intergranular pores and organic pores are the main pore types and the micropore types are clearly related to the mineral compositions and the TOC content.Vertically,the gas content is mainly affected by the TOC content.Horizontally,wells with high gas contents are distributed only southeast of the Huangling anticline,and the combination of structural styles,fault and fracture development,and the distribution of the regional unconformity boundary between the upper Sinian Dengying Formation(Z2d)and theЄ_(1)n^(2) are the three most important factors affecting the gas content.The favorable areas must meet the following conditions:a deep shelf environment,the presence of theЄ_(1)n^(1),wide and gentle folds,far from large normal faults that are more than 5 km,moderate thermal evolution,and greater than 500 m burial depth;this includes the block with the YD2–ZD2 wells,and the block with the Y1 and YD4 wells,which are distributed in the southern portion of the Huangling anticline and northern portion of the Xiannvshan fault.

Characteristics of greenhouse gas emission in three full-scale wastewater treatment processes

Three full-scale wastewater treatment processes, Orbal oxidation ditch, anoxic/anaerobic/aerobic （reversed A^2O） and anaerobic/anoxic/aerobic （A^2O）, were selected to investigate the emission characteristics of greenhouse gases （GHG）, including carbon dioxide （CO2）, methane （CH4） and nitrous oxide （N2O）. Results showed that although the processes were different, the units presenting high GHG emission fluxes were remarkably similar, namely the highest CO2 and N2O emission fluxes occurred in the aerobic areas, and the highest CH4 emission fluxes occurred in the grit tanks. The GHG emission amount of each unit can be calculated from its area and GHG emission flux. The calculation results revealed that the maximum emission amounts of CO2, CH4 and N2O in the three wastewater treatment processes appeared in the aerobic areas in all cases. Theoretically, CH4 should be produced in anaerobic conditions, rather than aerobic conditions. However, results in this study showed that the CH4 emission fluxes in the forepart of the aerobic area were distinctly higher than in the anaerobic area. The situation for N2O was similar to that of CH4： the N2O emission flux in the aerobic area was also higher than that in the anoxic area. Through analysis of the GHG mass balance, it was found that the flow of dissolved GHG in the wastewater treatment processes and aerators may be the main reason for this phenomenon. Based on the monitoring and calculation results, GHG emission factors for the three wastewater treatment processes were determined. The A^2O process had the highest CO2 emission factor of 319.3 g CO2/kg CODremoved, and the highest CH4 and N2O emission factors of 3.3 g CH4/kg CODremoved and 3.6 g N2O/kg TNremoved were observed in the Orbal oxidation ditch process.

Emissions of polycyclic aromatic hydrocarbons from coking industries in China

This study set out to assess the characteristics of polycyclic aromatic hydrocarbon （PAH） emission from coking industries, with field samplings conducted at four typical coke plants. For each selected plant, stack flue gas samples were collected during processes that included charging coal into the ovens （CC）, pushing coke （PC） and the combustion of coke-oven gas （CG）. Sixteen individual PAHs on the US EPA priority list were analyzed by gas chromatography/mass spectrometry （GC/MS）. Results showed that the total PAH concentrations in the flue gas ranged from 45.776 to 414.874 μg/m3, with the highest emission level for CC （359.545μg/m3）, The concentration of PAH emitted from the CC process in CP1 （stamp charging） was lower than that from CP3 and CP4 （top charging）. Low-molecular-weight PAHs （i.e., two- to three-ring PAHs） were predominant contributors to the total PAH contents, and Nap, AcPy, Flu, PhA, and AnT were found to be the most abundant ones. Total BaPeq concentrations for CC （2.248 μg/m3） were higher than those for PC （ 1.838 μg/m3 ） and CG （1.082 μg/m3 ）, and DbA was an important contributor to carcinogenic risk as BaP in emissions from coking processes. Particulate PAH accounted for more than 20% of the total BaPeq concentrations, which were significantly higher than the corresponding contributions to the total PAH mass concentration （5%）. Both particulate and gaseous PAH should be taken into consideration when the potential toxicity risk of PAH pollution during coking processes is assessed. The mean total-PAH emission factors were 346.132 and 93.173μg/kg for CC and PC, respectively.