Higher Gas Production Research Articles

The Analysis of Bio-Precursor Organic Matter Compositions and Its Significance for Gas Shale Reservoir of Wufeng–Longmaxi Formation from Dingshan Area, Sichuan Basin

In order to analyze the organic matter (OM) composition, this study carefully identified the OM types of 66 samples from Well A in the Dingshan area under microscope, and made an effort to obtain the semi-quantitative statistics contents of different bio-precursor derived OM. The results of OM content obtained under microscope showed a strong positive relationship (R2 = 0.85) with the TOC content analyzed by carbon–sulfur analyzer. The OM contained bethic algae debris, phytoplankton amorphous organic matter (AOM), acritarch, vitrinite-like particles, zooplankton (including graptolite, chitinozoa and others) and solid bitumen which was secondary formation OM. The phytoplankton AOM, graptolite and solid bitumen were the dominated OM in this interval. Solid bitumen (8%~11%) was filled at the bottom of the Wufeng Formation, which could be one reason for the high shale gas production in the lower part of this shale interval. N2 adsorption results showed that micropores and mesopores were predominant in this shale gas system, while pore volumes illustrated better positive relationships with organic matter than minerals, especially AOM content. Thus, both solid bitumen and AOM kerogen were the main sources for shale gas generation in this shale gas system.

Study on the Effect of Molecular Weight on the Gut Microbiota Fermentation Properties of Blackberry Polysaccharides In Vitro.

This study aimed to investigate the effect of different molecular weights on the metabolic characteristics of blackberry polysaccharides (BBP). After degradation, three fractions, namely, BBP-8, BBP-16, and BBP-24, were obtained. During fermentation, all polysaccharide fractions were significantly degraded and utilized by the intestinal microbiota, and the lower-molecular-weight polysaccharides were easier to be fermented with higher gas production and carbohydrate consumption rates. Furthermore, the monosaccharide utilization sequence of all polysaccharides was glucose > galactose > arabinose > galacturonic acid. In addition, the lower-molecular-weight polysaccharides had a faster short-chain fatty acid (SCFA) production rate but did not affect the final SCFA yields. The fermentation of BBP promoted the increase of Bacteroidetes and the decrease of Firmicutes. The proportions of Bacteroidetes in BBP, BBP-8, BBP-16, and BBP-24 were 45.41, 47.50, 48.08, and 50.09%, respectively.

Numerical comparison of different well configurations in the conditions of the 2020-gas hydrate production test in the Shenhu Area

The production trials in the Shenhu Area have proved that commercial level of gas production might be also obtained from low-permeable silty clayey-bearing hydrates as well. The numerical gas production simulations were conducted by using the TOUGH+HYDRATE simulator for different well configurations in the conditions of the 2020-gas hydrate production test well in the Shenhu Area. Higher gas production might be obtained with the horizontal well case and the deviated well cases rather than the vertical well. However, the commercial level of gas production from the Shenhu Area gas hydrates could not be obtained only with horizontal wells.

Nutritional Values and In Vitro Fermentation Characteristics of 29 Different Chinese Herbs

The present study evaluated the nutritional values and in vitro fermentation characteristics of 29 different Chinese herbs in order to develop effective feed additives for livestock nutrition. The Chinese herbs were analyzed for their chemical composition. The in vitro fermentation characteristics were evaluated using the gas production technique with swine cecal chyme inoculum. The results showed that the Allium tuberosum Rottl (Semen allii tuberosi, SAT) had the highest gross energy (GE), crude protein (CP), ether extract (EE), and total amino acid (TAA) contents, whereas Anemones raddeanae Rhizoma (Agstache rugosus, AR) had the highest crude fiber, neutral detergent fiber, and acid detergent fiber contents compared with the other Chinese herbs. The Rhus chinensis Mill (Chinese gall, CG), Scrophularia ningpoensis Hemsl (Radix scrophulariae, RS), Punica granatum L (Punica granatum L, PGL), Atractylodes macrocephala Koidz (White atractylodes rhizome, WAR), Sanguisorbae radix (Garden burnet, GB), Anemarrhena asphodeloides Bunge (Rhizoma anemarrhenaw, RA), and Rhei radix Et Rhizoma (Rheum officinale, RO) had a higher non-fiber carbohydrate content than the other Chinese herbs. The in vitro fermentation kinetic analysis showed that the RS, WAR, and RA had a higher gas production, a theoretical gas production, and a fractional rate of gas production than the other groups. Furthermore, the RA, WAR, RS, and Crataegi fructus (Crataegus pinnatifida Bun, CPB) had a higher total short-chain fatty acids (SCFAs) concentration, and CPB had the highest acetate concentration, whereas the WAR and RS had higher propionate and butyrate concentrations than the other groups. Moreover, the Isatis indigotica Fort (Folium isatidis, FI) and SAT had higher ammonia-N concentration than the other groups. In summary, among the 29 different Chinese herbs, the SAT had the highest nutritional value, which is reflected in the highest contents of GE, CP, EE, and TAA, whereas the RA, WAR, and RS showed better intestinal fermentation profiles, which is reflected in the higher fermentation degree and suitable SCFAs fermentation pattern. These findings provide a theoretical basis for using Chinese herbs as feed additives or microbial carbon sources in the intestines of animals.

Research on Erosion Wear of Slotted Screen Based on High Production Gas Field

Erosion wear is a common failure form of slotted screen in service. In this paper, based on CFD software and sand production data of a gas field in the Tarim Basin, the particle velocity and shear force at the slot of the flow field in the sieve tube were studied to determine the maximum area of erosion; at the same time, the velocity, viscosity, particle size and concentration of sand-carrying fluid were analyzed by orthogonal test, and the regression model of multi-factor maximum erosion rate was established. ① Through the analysis of the four factors on the degree of dependent variables, the order of the primary and secondary factors are: sand-carrying liquid flow rate, particle concentration, fluid viscosity, particle diameter, the effect of fluid viscosity and particle diameter on erosion rate is relatively small; ② According to the analysis of variance and range, the combination scheme of minimum erosion generation is obtained, and the calculation model of the erosion rate of the slotted screen is established. In order to reduce the erosion and abrasion in the actual oil and gas production process, the reasonable flow control and precise sand control method design and precision selection can be adopted; it provides a design basis for sand control and long-term effects of production in high-yield gas field.

In vitro fermentative characteristics and chemical quality of tanzania grass with organic and chemical fertilization

Objective: To evaluate the chemical quality and in vitro fermentative characteristics to find the optimum cutting point of Panicum maximum cv. tanzania grass under four fertilization schemes. 
 Methodology: The grass was tanzania, which received chemical (F1), vermicompost (F2), compost (F3) and compost+lixiviate (F4) fertilizations. The grass was cut at 20, 35, 50, 50, 65, 80 and 105 days. Neutral detergent fiber (NDF), acid detergent fiber (ADF), crude protein (CP), dry matter (DMD), NDF (NDFD) and ADF (ADFD) degradations and in vitro gas production were determined. The experimental design was a 4x6 factorial arrangement in a completely randomized system with fertilization and days of cutting as factors.
 Results: F3-65, F1-65, F4-80 and F1-8 d higher NDF content; F1-65 d higher ADF; F1-20 d higher CP (p≤0.05). F4-50 and F2-50 d higher gas production; F4-20, F4-35, F4-50, F2-20, F2-35, F1-20 d higher DMD, F2-20 and F4-20 d higher NDFD; F4-20, F4-35, F4-65 and F2-20 d higher ADFN (p≤0.05).
 Limitations/implications: Lack of previous research studies on organic fertilization of tanzania.
 Conclusions: Fertilization with vermicompost or compost+lixiviate improve chemical content, in vitro gas production and degradations of tanzania grass

Pyrolysis characteristics and microstructure evolution of different coal types

Coal pyrolysis is the basis of coal gasification, as it is the necessary reaction step in the coal conversion process. To study the pyrolysis characteristics of different coal grades under temperature, thermal simulation tests of three different ranks of coal were conducted, and the pore structure and gas products were analyzed by using liquid nitrogen adsorption and gas chromatographic, and perform fractal fitting for pores of different size. The results show that the pyrolysis gas output of Inner Mongolia lignite is higher than that of Xinjiang long flame coal and Hancheng bituminous coal. With the increase of coal rank, the gas output of each gas component also shows a decreasing trend and the initial temperature and peak temperature of various gases gradually shift to high temperature. With the increase of temperature, the average pore size, volume, specific surface area, and fractal dimension of the three kinds of coal char show an increasing trend. The average pore size and pore volume of coal char increase, and the fractal dimension increase with the increase of coal rank. The comprehensive comparative analysis of the gaseous products, average pore size, pore volume, and fractal dimension of the three coal chars shows that Inner Mongolia lignite has high gas production, large average pore size, good connectivity, and simple pore structure, which is conducive to the escape of pyrolysis gas and the transportation of gasification agent and is the best favorable coal for gasification. The research results are expected to provide experimental guidance for the actual production of underground coal gasification.

Three-Dimensional CFD simulation of waste plastic (SRF) gasification in a bubbling fluidized bed with detailed kinetic chemical model

The utilization of municipal solid waste combustible fractions as a fuel is generally preferred over landfilling. Fuels derived from waste materials, such as solid refuse fuel (SRF), can be utilized for energy generation using pyrolysis, gasification, and combustion. A three-dimensional computational fluid dynamics (CFD) model was developed for the simulation of SRF gasification process in a bubbling fluidized bed (BFB). The gas phase and solid phase were studied using the large eddy simulation (LES) approach and the multiple particle-in-cell (MP-PIC) method, respectively. The simulation included the chemical kinetic model of SRF drying, pyrolysis, gas–solid reactions, and homogeneous reactions. The kinetic chemistry model was expanded to reflect a higher yield of C2-C3 gases and tars evolved from SRF. The simulation results were compared with the gas composition obtained from experiments conducted on a lab-scale reactor having a capacity, height, and internal diameter of 1 kg/h, 1 m, and 0.114 m, respectively. The independence of the accuracy of the model on the mesh resolution and computational particle number was examined. Varying air-to-fuel equivalence ratio (ER) to 0.20, 0.25, and 0.30 changed syngas LHV to 25.40, 16.86, and 14.30 kJgas/gfuel respectively and changed C2-C3 hydrocarbons yield to 0.30, 0.18, and 0.16 g/gfuel respectively. Changing the SRF feed location to below the bed at ER = 0.25, increased the gas LHV to 19.85 kJgas/gfuel and increased C2-C3 hydrocarbons yield to 0.21. SRF BFB gasification reactor model can be exploited for simulation of low ER autothermal decomposition of SRF to C2-C3 hydrocarbons or high LHV gas production.

High temperature flash pyrolysis characteristics of waste plastics (SRF) in a bubbling fluidized bed: Effect of temperature and pelletizing

Utilization of municipal solid waste (MSW) non-recyclable combustible fractions abundant in mixed plastics such as solid recovered fuel (SRF) is becoming increasingly widespread due to its sustainability. This study investigates utilization of pelletized mixed plastic SRF using fluidized bed (FB) flash pyrolysis at high temperature, unlike previous studies that focused on low temperature pyrolysis. The effect of temperature on the pyrolysis of SRF was investigated using an externally heated bubbling fluidized bed (BFB) reactor having an internal diameter of 0.114 m and a height of 1 m. Experiments were conducted with an inert fluidizing agent (N2) in the temperature range of 600–900 °C. The pyrolysis products such as gas, char, and tar were analyzed, and the mass balance was determined. High temperature flash pyrolysis favors production of high LHV product gas unlike previous studies which were mostly focusing on liquids production. The gas yield increases from 0.285 g/gfuel to 0.680 g/gfuel with increasing temperature from 600 °C to 900 °C. GC–MS analysis of the tar revealed that increasing the temperature intensifies the cracking of naphthenes, alcohols, and olefins, and increases the relative percentage of aromatic hydrocarbons up to 85.1 % at 900 °C. When fluffy SRF was pyrolyzed, gas yield was slightly higher than the pelletized SRF at 800 °C suggesting that low temperature gradient increases gas yield and decreases char yield. Fluffy SRF pyrolysis tar also mainly consists of aromatics and esters. The process produces high calorific gas and reveals the reaction mechanisms relevant to gasification processes.

Numerical simulation and sensitivity analysis of automatic optimization of gas extraction well locations in abandoned mines

There are large numbers of abandoned mines in China and abroad, among of which stores relative abundant coal-bed gas. The gas extraction from abandoned mines can be used for power generation or industrial gas utilization. In this paper, the present situation of abandoned mines in China and abroad was studied, and the disadvantages of the common layout and optimization methods of gas extraction in abandoned mines were pointed out. Based on the analysing of reservoir conditions and physical property parameters, the finite element software COMSOL was used to do the numerical simulation of extraction well automatically optimize, and take shenbei coal mine as an example. Moreover, an automatic optimization APP of well location was developed based on the results of simulation. Finally, the parameter sensitivity of gas extraction is analysed. Through the study, it is found that the most basic and common method of gas extraction in abandoned mines is empirical method, which lacks of theoretic support and accuracy, thus causing unreasonable extraction and waste of resources. In this study, the COMSOL numerical simulation software was used to explore the numerical simulation method of automatic well position optimization combined with the optimization algorithm. The Nelder-Mead algorithm was selected as the optimization algorithm after comparing the advantages and disadvantages of various algorithms. The operation flow and type of Nelder-Mead algorithm were analysed, and the optimization parameters of numerical simulation were set. Through the numerical simulation, the function of automatically searching the high-gas production position near the preset well position was realized, and the automatic optimization APP for gas extraction in abandoned mines was developed. Finally, the sensitivity of parameters to gas production in different well locations under three different pumping conditions which are horizontal, vertical and bottom-hole negative pressure was analysed; and the simulation results were discussed.

Determination of the degree of coal deformation and its effects on gas production in the southern Qinshui Basin, North China

Coal deformation significantly impacts coalbed methane (CBM) productivity. However, existing methods are incapable of quantitatively evaluating coal deformation on a high accuracy when there is limited core recovery from a CBM well. This study proposes a well logging coal structure index (WCSI) to quantify the degree of coal deformation. The WCSI of targets is calculated based on the data from well logs and coal cores, and it can also be estimated from well logs when no coal cores are recovered from wells. Thus, the WCSI can be applied to the regional-scale evaluation of coal deformation degree, and its effectiveness has been validated by data for 245 samples from the No. 3 coal seam in 55 exploration wells in the southern Qinshui Basin (SQB). Results indicate that the reservoir permeability and hydraulic fracturing effectiveness depend on the degree of coal seam deformation, which further affects the unique distribution of gas production in the known production regions in the SQB. Generally, the lowly deformed coal seam (WCSI (avg.) < 40) occurs mainly in the tectonically ‘stable’ regions (no faults or only small-scale faults development) where the micro-fractures/cleats in coal are not well developed. Low WCSI (avg.) commonly indicates low permeability (<0.06 mD) and poor hydraulic fracturing of the reservoir, resulting in relatively low gas production rate of wells in these regions. Secondly, the moderately deformed coal seam (40 < WCSI (avg.) < 60) is mainly found in areas close to moderate-scale faults, where coal seams have relatively high reservoir permeability (>0.06 mD) and hydraulic fracturing is easiest. This causes high gas production rate from wells in these regions. Thirdly, the highly deformed coal seam (WCSI (avg.) > 60) is generally found close to large-scale faults, indicating very low reservoir permeability (<0.03 mD) and the worst effectiveness from hydraulic fracturing of the reservoir, resulting in the lowest gas production rate of wells in these regions. In summary, the production efficiency from CBM wells in the SQB can thus be described in terms of the WCSI (avg.) value, and hence this parameter can help with preliminary forecasting gas production.

Impact of distinct levels swimming crab shell powder (Portunus pelagicus) supplementation on in vitro rumen fermentation properties processed with phosphoric acid as a chitosan source

The major goal of this study was to see how adding swimming crab shell to dietary feed affected in vitro gas production and fermentation of feed in ruminal fluid Completely Randomized Design (CRD) with five treatments and four replications was arranged on this research. The treatments are RJ0 as control negative (0% of SCS supplementation of DM), RJ1(10% SCS), RJ2 (20% SCS supplementation), RJ3 (30% SCS supplementation), and RJ4 as possitive control (1% commercial chitosan supplementation). The highest gas production given by RJ0 treatment than other treatment. Total gas production 1-48 hours, rate of gas production (c), microbial cell protein, IVDMD, IVOMD of supplementation of SCS was significantly affected by treatments (P<0.05). Gas production from total fraction (a+b), soluble fraction (a) and insoluble fraction (b), NH3 production, and ammount of protozoa indicated no significant difference (P>0.05) among treatments. In this study basal diets supplemented with 30% SCS treatment had the best result as chitosan source on rumen fermentation properties in vitro.

Catalytic Synthesis of Carbon Nanotubes by Ni/ZSM-5 Catalyst from Waste Plastic Syngas

Carbon nanotubes (CNTs) have been proved to be a high-value by-product of hydrogen production which could be obtained through catalytic reforming from waste plastic syngas. Catalyst plays an important role in the growth of carbon nanotubes. The influences of Ni/ZSM-5 catalyst and temperature were performed in a lab-scale tubular reactor. The catalyst and produced carbon were analyzed by different characterization methods. X-ray diffraction, X-ray energy dispersive spectrometer, scanning electron microscopy and transmission electron microscopy. The results showed that in the presence of catalyst, 600 °C is considered the optimal temperature during the operating temperature range of 400 °C~800 °C for carbon yield and hydrogen production rate, the highest carbon yield of 4.83 g/gcatalyst (among which the MWCNTs were the main products) and hydrogen production rate of 0.0199 L/min were obtained. Higher catalytic temperature led to higher average diameter of carbon nanotubes, which increased from 39.5 nm to 55.3 nm. The highest carbon nanotubes proportion of 98.08% to total carbon deposition was obtained under the conditions of 800 °C. It suggested that Ni/ZSM-5 catalyst has the potential for high quality carbon nanotubes and H2-riched gas production from waste plastic syngas.

Effects of Catalytic Promoter Mn on Ni/ZSM-5 Catalyst to Catalyst Waste Plastic Syngas to Prepare Carbon Nanotubes for Co-Production of Hydrogen

Carbon nanotubes (CNTs) produced by catalytic reforming of the waste plastic syngas is a high value-added by-product of hydrogen production. Catalysts play an important role in the growth of carbon nanotubes. The influences of Ni/ZSM-5 catalyst, Ni–Mn/ZSM-5 catalyst and temperature were performed in a lab-scale tubular reactor. The catalysts and product carbon were analyzed by different characterization methods, including temperature-programed reduction/oxidation, X-ray diffractometer, scanning electron microscope, transmission electron microscope, X-ray energy spectrometer. The results showed that in the presence of Ni–Mn/ZSM-5 catalyst with the addition of catalytic promoter Mn, 650 °C was the optimum temperature during the operating temperature range of 600 °C~800 °C for the rate of carbon production and hydrogen production, and the carbon production was the highest, which was 2.95gCNTs/gCatalyst (wherein the Multi-walled carbon nanotubes (MWCNTs) were main product), and compared with the monometallic Ni/ZSM-5 catalyst, the Ni–Mn/ZSM-5 catalyst with Mn addition increased the H2 content in the syngas from 14 Vol.% to 39 Vol.%. The highest carbon nanotubes proportion of 95.81% to total carbon deposition was obtained under the conditions of 750 °C. The introduction of catalytic promoter Mn transforms the growth mode of carbon nanotubes from top growth mode to bottom growth mode, and obtains carbon nanotubes with more regular structure. It suggested that Ni–Mn/ZSM-5 catalyst had the potential for high quality carbon nanotubes and H2-riched gas production from waste plastic syngas.

Model-based life cycle control of ICVs in injectors in a benchmark analogous to a pre-salt field

Some fields in the Brazilian pre-salt feature light oil and high gas/CO2 content, which is a bottleneck to oil production due to gas processing restrictions in the facilities. To deal with this, Water-alternate-gas (WAG) is used as a recovery mechanism while the use of Interval Control Valves (ICVs) is also recommended, since these enable controlling the production or injection through segments in the wells.In this context of high gas production and WAG, a good injection management is crucial and the use of ICVs in the injection wells can help to improve the oil production and the field's economic return. In this work, we propose and compare four approaches (A, B, C, and D) to control the ICVs of the injectors considering numerical simulation and Net present value (NPV) as objective function. Approaches A and B use streamlines to correlate producers and injectors, and they also use the Gas-oil ratio (GOR) of the producers as a monitoring variable to close the valves of the injectors. The difference between them is that, in Approach A, the valves remain closed during the entire field's life cycle, while there is an alternation of each opened or closed valve for every WAG cycle in Approach B. In Approach C, the alternation between each valve is made since the beginning of the WAG cycles, instead of waiting for a trigger to start closing the valves. These three approaches are sub-divided into other (minor) approaches, depending on whether the valve remains closed, or not, during the water injection cycles. Finally, in Approach D, we attempt to control the cumulative fluid injection between the zones of the injectors. The study is applied to the SEC1_2022 benchmark case, a synthetic model analogous to a pre-salt field. Finally, we apply the best approach found to a reference case (“true response”) to assess how the proposed strategy would behave in real cases.The results indicate that closing the valves in earlier stages of the field's life cycle is better than using GOR as a trigger. Furthermore, the alternation between opened and closed valves proved to be the best way to control the valves in this case. Approach D was the best among those evaluated, with the highest increase in oil production and greatest decrease in water production, providing highest NPV. Although the platform remained constrained by gas production, this approach provided a better fluid distribution in the field and among wells, improving both oil recovery and economic returns.

New understandings on gas accumulation and major exploration breakthroughs in subsalt Ma 4 Member of Ordovician Majiagou Formation, Ordos Basin, NW China

Geological conditions and main controlling factors of gas accumulation in subsalt Ma 4 Member of Ordovician Majiagou Formation are examined based on large amounts of drilling, logging and seismic data. The new understandings on the control of paleo-uplift over facies, reservoirs and accumulations are reached: (1) During the sedimentary period of Majiagou Formation, the central paleo-uplift divided the North China Sea in central-eastern of the basin from the Qinqi Sea at southwest margin of the basin, and controlled the deposition of the thick hummocky grain beach facies dolomite on platform margin of Ma 4 Member. Under the influence of the evolution of the central paleo-uplift, the frame of two uplifts alternate with two sags was formed in the central-eastern part of the basin, dolomite of inner-platform beach facies developed in the underwater low-uplift zones, and marl developed in the low-lying areas between uplifts. (2) From the central paleo-uplift to the east margin of the basin, the dolomite in the Ma 4 Member gradually becomes thinner and turns into limestone. The lateral sealing of the limestone sedimentary facies transition zone gives rise to a large dolomite lithological trap. (3) During the late Caledonian, the basin was uplifted as a whole, and the central paleo-uplift was exposed and denuded to various degrees; high-quality Upper Paleozoic Carboniferous—Permian coal measures source rocks deposited on the paleo-uplift in an area of 60 000 km2 providing large-scale hydrocarbon for the dolomite lithological traps in the underlying Ma 4 Member. (4) During the Indosinian—Yanshanian stage, the basin tilted westwards, and central paleo-uplift depressed into an efficient hydrocarbon supply window. The gas from the Upper Paleozoic source rock migrated through the high porosity and permeability dolomite in the central paleo-uplift to and accumulated in the updip high part; meanwhile, the subsalt marine source rock supplied gas through the Caledonian faults and micro-fractures as a significant supplementary. Under the guidance of the above new understandings, two favorable exploration areas in the Ma 4 Member in the central-eastern basin were sorted out. Two risk exploration wells were deployed, both revealed thick gas-bearing layer in Ma 4 Member, and one of them tapped high production gas flow. The study has brought a historic breakthrough in the gas exploration of subsalt Ma 4 Member of Ordovician, and opened up a new frontier of gas exploration in the Ordos Basin.

Hydrocarbon Gases in Seafloor Sediments of the Edge Shelf Zone of the East Siberian Sea and Adjacent Part of the Arctic Ocean

The continental margins of the East Siberian Sea and Arctic Ocean are among the Earth’s most inaccessible marine environments for hydrocarbon research due to the almost year-round presence of ice cover. Despite this, limited preliminary assessments which have been carried out to date have all yielded some indication of high oil and gas production potential in these regions. This article presents the results of gas-geochemical studies of seafloor sediments of the East Siberian Sea, obtained in three expeditions onboard the R/V “Akademik Lavrentiev” in 2008 (LV45), 2016 (LV77), and 2020 (LV90). The composition of sorbed hydrocarbon gases in seafloor sediments was analyzed. In addition, the stable isotopic composition of carbon was determined for CH4, C2H6, and CO2 in gases, which were desorbed from marine sediments. The sediments were also analyzed for organic matter content. Despite the absence of observable gas seepage directly into the water column, at some stations, increased concentrations of methane and hydrocarbon gases were encountered, indicating the widespread predominance of thermogenically derived gases. We present a hydrocarbon classification system which delineates eight identifiable sources of regional gas occurrences (coal gas, igneous rocks, solid bitumen, condensate-gas, gas-condensate, oil gas, gas oil, and oil gases). A stable isotopic analysis of carbon in CH4, C2H6, and CO2 indicates varying degrees of mixing between a shallow, early-kerogen gas source and a deeper mantle carbon source in some areas of the study.

Optimal design of the field hydrate production test in the offshore India: Insights from the vertically heterogeneous hydrate reservoir model

Recently, the hydrate-bearing sand reservoirs were founded with high saturation in the offshore India by the National Gas Hydrate Program Expedition 02 (NGHP-02). Based on the detailed geological data at the NGHP-02-16 site, a more realistic reservoir model is constructed to analyze the unique multiphase flow and hydrate phase change behaviors from the geologically descriptive hydrate reservoirs. The main goals of this work are to optimize the adjustable production parameters and to predict the long-term gas production performance for guiding the upcoming field hydrate production test in India. The results indicate that gas production rates increase, but water production rates decrease slowly with time from the heterogeneous hydrate-reservoir. This is completely different from the previous prediction of multiphase flow behavior based on homogeneous hydrate-reservoir models. A non-uniform hydrate dissociation front is formed in the hydrate-reservoir due to the reservoir heterogeneity promote the horizontal dissociation of solid-hydrate within the high permeability sand layers. The maximum distance of free gas zone expands to outside more than 500 m from the production well. This indicates that the field fault system should be carefully concerned during the long-term production. Sensitivity analysis results suggest that the complete perforation in the hydrate-bearing layer and the underlying water saturated layer is beneficial for improving the hydrate production performance. Over the 5 years depressurization, a total of 2.08 × 107 ST m3 methane gas can be produced using the recommended well placement. The average gas-to-water ratio and energy ratio reach 10.22 ST m3 CH4/m3 H2O and 30.14, respectively, showing a high gas production potential from this hydrate site.

Enhanced gas production of silty clay hydrate reservoirs using multilateral wells and reservoir reformation techniques: Numerical simulations

Multilateral wells and reservoir reformation techniques are widely employed to increase yield for spatially heterogeneous oil and gas reservoirs. However, the multilateral wells integrated with reservoir reformation have not been evaluated for low-permeability silty clay hydrate reservoirs before. Here, the multilateral well schemes without and with reservoir reformation technologies including burden sealing and hydraulic slotting were proposed, and their production behaviors under depressurization were evaluated and compared to that of a vertical well using available data in the South China Sea. The results show that the multilateral wells significantly enhance gas extraction because of a synergistic inter-borehole depressurization and an increase in production interval. Increasing branch hole number can further promote the synergistic effect and involved area, which enhances more hydrate dissociation, but this stimulation effect decreases with the extension of the production cycle in the silty clay reservoirs. The multilateral well with the hydraulic slotting is more suitable for short-term field trials and the burden sealing is better for long-term gas recovery. Combining hydraulic slotting or fracture and burden sealing technique at different production stages would be an extremely promising way for a multilateral well design to achieve long-term stable and high gas production in the low-permeability hydrate reservoirs.

Coal-direct chemical looping hydrogen generation with BaMnO3 perovskite oxygen carrier

Coal-direct chemical looping hydrogen generation (CDCLHG) is a novel process that uses coal to directly produce H2 with inherent CO2 capture. A key issue is to find out suitable oxygen carriers for this process. In this study, perovskite was proposed as the oxygen carrier for CDCLHG, and a series of Mn-based and Fe-based perovskite oxides were synthesized by a sol-gel method for CDCLHG reactions in a fixed-bed reactor. The results showed that BaMnO3 was an optimal oxygen carrier for CDCLHG, which could obtain H2-rich gas (>85%) with a high H2 gas production rate, about 13 times higher than that in char steam gasification. Further tests showed that the optimal reaction temperature and O/C ratio were 850 °C and 1: 0.05, respectively. XRD and XPS patterns indicated that part of the lattice oxygen in BaMnO3 could convert to the carbonate oxygen in BaCO3 during the fuel oxidation stage (FO stage) and obtained BaMnO3-δ with plentiful oxygen vacancies in it. The BaMnO3-δ could partially restore its lattice oxygen in the reduction of steam stage (RS stage) and completely recover its initial structure in the air calcining stage (AC stage). SEM images showed that the decrease of BaMnO3 reaction performance after 9 cycles was mainly due to ash accumulation.