Upper Paleozoic coal measures and unconventional natural gas systems of the Ordos Basin,China

Upper Paleozoic coal measures in the Ordos Basin consist of dark mudstone and coal beds and are important source rocks for gas generation. Gas accumulations include coal-bed methane （CBM）, tight gas and conventional gas in different structural areas. CBM accumulations are mainly distributed in the marginal area of the Ordos Basin, and are estimated at 3.5 × 1012 m3. Tight gas accumulations exist in the middle part of the Yishan Slope area, previously regarded as the basin-centered gas system and now considered as stratigraphic lithologic gas reservoirs. This paper reviews the characteristics of tight gas accumulations： poor physical properties （porosity 〈 8%, permeability 〈 0.85 × 10 3 μm2）, abnormal pressure and the absence of well-defined gas water contacts. CBM is a self-generation and self- reservoir, while gas derived from coal measures migrates only for a short distance to accumulate in a tight reservoir and is termed near-generation and near-reservoir. Both CBM and tight gas systems require source rocks with a strong gas generation ability that extends together over wide area. However, the producing area of the two systems may be significantly different.

The control of coal mine gas and coordinated exploitation of coal bed methane in China

Based on the characteristics of the coalfield geology and the distribution of coalbed methane (CBM) in China,the geological conditions for exploiting the CBM and drainingthe coal mine gas were analyzed,as well as the characteristics of CBM production.Bycomparing the current situation of CBM exploitation in China with that in the United States,the current technology and characteristics of the CBM exploitation in China were summarizedand the major technical problems of coal mine gas control and CBM exploitationanalyzed.It was emphasized that the CBM exploitation in China should adopt the coalmine gas drainage method coordinated with coal mine exploitation as the main model.Itwas proposed that coal mine gas control should be coordinated with coal mine gas exploitation.The technical countermeasure should be integrating the exploitation of coal andCBM and draining gas before coal mining.

Characteristics of compression fracture of ＂three soft＂ coal bed by perfusion and gas sucking technique

Against the particularity of stratum-structure in ＂three soft＂ mine areas, according to rock indoor test and on-site sucking experiment, discussed the characteristics of argillization, compression fracture and sucking technique of soft coal with low permeability. It is clearly pointed out that the gas can be highly effectively sucked only by compression fracture along the occurrence of the coal seam, creating inter-seams crack belt because of the difference of bulgy deformation. After the flooding experiment in the 24080 workface of Pingdingshan No. 10 mine, the average single-bore volume of gas increases from 77 m3 to 7 893 mS, while decay cycle extended from 7 days to 80-90 days. Also, the single-bore extracting rate of gas increases to 33%.

Motion analysis of waste rock in gas-solids fluidized bed in coal dry beneficiation

Through the analysis of forces acting on the waste rock in the gas solid fluidized bed, the waste rock velocity equations and displacement equations in the gas solids fluidized bed were achieved and the influential factors of the waste rock motion in the fluidized bed were studied in this paper. The conclusions show that the primary factors influencing the waste rock motion are the waste rock grain size and the scraper velocity according to the computer simulation. This has provided the theoretical foundation both for improving the separating effect and ascertaining the length of the separating cell.

Balance Analysis of Profit and Loss on Exploiting Coal-Bed Gas in China

Models about four aspects according to the balance principle and practice in China were established, which involve the minimum production scale, alert production scale, safe running scale, and the goal production scale for specified profit level. It provides an effective quantitative analyzing method for the investors of coal bed gas exploitation project.

Recovery of greenhouse gas as cleaner fossil fuel contributes to carbon neutrality

Under the context of carbon neutrality of China,it is urgent to shift our energy supply towards cleaner fuels as well as to reduce the greenhouse gas emission.Currently,coal is the main fossil fuel energy source of China.The country is striving hard to replace it with methane,a cleaner fossil fuel.Although China has rich geological resources of methane as coal bed methane(CBM)reserves,it is quite challenging to utilize them due to low concentration.The CBM is however mainly emitted directly to atmosphere during coal mining,causing waste of the resource and huge contribution to greenhouse effect.The recent work by Yang et al.demonstrated a potential solution to extract low concentration methane selectively from CBM through using MOF materials as sorbents.Such kind of materials and associated separation technology are promising to reduce greenhouse gas emission and promote the methane production capability,which would contribute to carbon neutrality in dual pathways.

Advances of nanotechnologies for hydraulic fracturing of coal seam gas reservoirs:potential applications and some limitations in Australia

Some of the most promising potential applications of nanotechnology to hydraulic fracturing of coal seam gas(CSG)are reviewed with a focus on Australian CSG wells.Three propitious applications were identifed:(1)Nanoparticle enhanced viscoelastic surfactants(VES)fracturing fuids to prevent fuid loss by up to 30%,made possible by the formation of pseudo-flter cakes and reducing the viscosity of the VES fuids.Besides,there is no requirement of clay control additives or biocides.(2)Nano-proppants to extend fracture networks and reduce proppant embedment by introducing them prior to the emplacement of larger proppants.Fly Ash nanoparticles can be particularly efective because of their high sphericity and mechanical strength.(3)Nanoparticle-coated proppants,to mitigate the migration of particle fnes by restricting them close to their source by adsorption,with MgO being the most efective.The use of nanotechnology in hydraulic fracturing applications is currently hindered due to a discordant regulatory environment compounded by the cost of the nanoparticles themselves,as well as,a lack of feld data to validate the technology under real downhole conditions.Although the necessary feld tests are unlikely to be conducted for as long as abundant natural gas is available,exploratory studies could pave the way for future applications.

Calculation of gas content in coal seam influenced by in-situ stress grads and ground temperature

On the basis of the analysis of coal bed gas pressure in deep mine, and the coal bed permeability ( k ) and the characteristic of adsorption parameter ( b ) changing with temperature, the author puts forward a new calculating method of gas content in coal seam influenced by in situ stress grads and ground temperature. At the same time, the contrast of the measuring results of coal bed gas pressure with the computing results of coal bed gas pressure and gas content in coal seam in theory indicate that the computing method can well reflect the authenticity of gas content in coal seam,and will further perfect the computing method of gas content in coal seam in theory,and have important value in theory on analyzing gas content in coal seam and forecasting distribution law of gas content in coal seam in deep mine.

Evaluation of coal bed methane content using BET adsorption isotherm equation

Coal bed methane is unconventional raw natural gas stored in coal seam with considerable reserves in China.In recent years,as the coal bed methane production,the safety and the use of resources have been paid more attentions.Evaluating coal bed methane content is an urgent problem.A BET adsorption isotherm equation is used to process the experimental data.The various parameters of BET equation under different temperatures are obtained;a theoretical gas content correction factor is proposed,and an evaluation method of actual coal bed methane is established.

Investigation of thermochemical process of coal particle packed bed reactions for the development of UCG

In this study,a packed bed reactor was developed to investigate the gasification process of coal particles.The effects of coal particle size and heater temperature of reactor were examined to identify the thermochemical processes through the packed bed.Three different coal samples with varying size,named as A,B,and C,are used,and the experimental results show that the packed bed with smaller coal size has higher temperature,reaching 624°C,582°C,and 569°C for coal A,B,and C,respectively.In the case of CO formation,the smaller particle size has greater products in the unit of mole fraction over the area of generation.However,the variation in the porosity of the packed bed due to different coal particle sizes affects the reactions through the oxygen access.Consequently,the CO formation is least from the coal packed bed formed by the smallest particle size A.A second test with the temperature variations shows that the higher heater temperature promotes the chemical reactions,resulting in the increased gas products.The findings indicate the important role of coal seam porosity in underground coal gasification application,as well as temperature to promote the syngas productions.

A continuous and high-efficiency process to separate coal bed methane with porous ZIF-8 slurry:Experimental study and mathematical modelling

Coal bed methane has been considered as an important energy resource.One major difficulty of purifying coal bed methane comes from the similar physical properties of CH_4 and N_2.The ZIF-8/water-glycol slurry was used as a medium to separate coal bed methane by fluidifying the solid adsorbent material.The sorption equilibrium experiment of binary mixture(CH_4/N_2)and slurry was conducted.The selectivity of CH_4 to N_2 is within the range of 2-6,which proved the feasibility of the slurry separation method.The modified Langmuir equation was used to describe the gas-slurry phase equilibrium behavior,and the calculated results were in good agreement with the experimental data.A continuous absorption-adsorption and desorption process on the separation of CH_4/N_2 in slurry is proposed and its mathematical model is also developed.Sensitivity analysis is conducted to determine the operation conditions and the energy performance of the proposed process was also evaluated.Feed gas contains 30 mol%of methane and the methane concentration in product gas is 95.46 mol%with the methane recovery ratio of 90.74%.The total energy consumption for per unit volume of product gas is determined as 1.846 kWh Nm^(-3).Experimental results and process simulation provide basic data for the design and operation of pilot and industrial plant.

Optimization strategy and procedure for coal bed methane separation

Coal bed methane （CBM） has a huge potential to be purified to relieve the shortage of natural gas meanwhile to weaken the greenhouse effect. This paper proposed an optimal design strategy for CBM to obtain an integrated process configuration consisting of three each single separation units, membrane, pressure swing absorption, and cryogenics. A superstructure model was established including all possible network configurations which were solved by MINLP. The design strategy optimized the separation unit configuration and operating conditions to satisfy the target of minimum total annual process cost. An example was presented for the separation of CH4/N2 mixtures in coal bed methane （CBM） treatment. The key operation parameters were also studied and they showed the influence to process configurations.

Effect of bubbles addition on teetered bed separation

To improve the separation efficiency of a conventional Teetered Bed Separator(TBS) in beneficiation of fine coal with a wide size range,an Aeration TBS(A-TBS) was proposed in this investigation.The bubbles were introduced to A-TBS by a self-priming micro-bubble generator.This study theoretically analyzed the effect of bubbles on the difference in hindered settling terminal velocity between different density particles,investigated the impact of superficial water velocity(V_(SW)) and superficial gas velocity(V_(Sg)) on bed fluidization,and compared the performance of the TBS and A-TBS in treating 1-0.25 mm size fraction particles.The results show that the expansion degree of fluidized bed which was formed by different size particles or has different initial height,is increased by the introduction of bubbles.Compared with the TBS,at the same level of clean coal ash content,the A-TBS shows an increase in the combustible recovery of clean coal,ash content of tailings,and practical separation density by 5.26%,6.56%,and 0.088 g/cm3 respectively,while it shows a decrease in the probable error(E_p) and V_(SW) by 0.031 and 3.51 mm/s,respectively.The addition of bubbles at a proper amount not only improves the separation performance of TBS,but also reduces the upward water velocity.

Impact of Reservoir Properties on the Production of the Mannville Coal Measures, South Central Alberta from a Numerical Modelling Parametric Analysis

Numerical simulations are used to investigate the impact of intrinsic and extrinsic reservoir properties on the production from coal and organic rich lithologies in the Lower Cretaceous Mannville coal measures of the Western Canadian Sedimentary Basin. The coal measures are complex reservoirs in which production is from horizontal wells drilled and completed in the thickest coal seam in the succession (1 m versus 3 m), which has production and pressure support from thinner coals in the adjacent stratigraphy and from organic-rich shales interbedded and over and underlying the coal seams. Numerical models provide insight as to the relative importance of the myriad of parameters that may impact production that are not self-evident or intuitive in complex coal measures.

Decomposition of carbon dioxide hydrate in the samples of natural coal with different degrees of metamorphism

Methane and carbon dioxide hydrates are one of the possible forms in which these gases exist in natural coal(for more detailed discussion see Refs [1,2]). In this work, the decomposition of carbon dioxide hydrate in five samples of natural coal differing from each other in metamorphism degree was investigated experimentally. Carbon dioxide hydrate dispersed in coals was synthesized from water adsorbed in these coals. During a linear temperature rise in an autoclave with the coal + hydrate sample the hydrate decomposition manifests itself as a step of increase in gas pressure, accompanied by a decrease/stabilization of the temperature of coal sample. The dependencies of the amount of hydrate formed on initial coal humidity and on gas pressure during hydrate formation were studied. It was demonstrated that each coal sample is characterized by its own humidity threshold below which hydrate formation in natural coal is impossible. With an increase in gas pressure, the amount of water transformed into hydrate increases. For the studied coal samples, the decomposition of carbon dioxide hydrates proceeds within a definite temperature and pressure range, and this range is close to the curve of phase equilibrium for bulk hydrate.

Importance of Well Spacing and Orientation for Multi-Lateral Pads on Production: Learnings from Production Analysis and Numerical Modelling of the Mannville Coal Measures, South Central Alberta

The modelling results from numerical simulations of the Early Cretaceous, Mannville coal measures with anisotropic permeability provide insights into development strategies not readily visualized or otherwise intuitive. The complex relationships between water and gas production, the contribution from multiple coal seams as well as from organic rich shales, and the impact of well interference combined with anisotropic fracture permeability are investigated through a series of numerical simulations of four well-pads (on the corners of a square mile of land with decreasing well spacing from 1, 3, to 4 laterals per pad). After 25 years of production, the two pads with optimally-oriented laterals with respect to the fracture permeability anisotropy produce 61% of the recovered gas for the 1 lateral/pad model, 52% for the 3 laterals/pad model, and 50% for the 4 laterals/pad model. Downspacing has a greater impact on increasing the gas production from pads with the poorly-oriented main laterals than from the pads with the optimally-oriented main laterals. The cumulative gas production at the end of the 25 year history is 4.2% higher for an optimally-oriented pad (pad1) and 1.1× higher for a poorly-oriented pad (pad3) for a model with 4 laterals/pad than 3 laterals/pad and an optimally-oriented pad is 1.1% higher for an optimally-oriented pad and 1.5× higher for a poorly-oriented pad for a model with 3 laterals/pad than 1 lateral/pad. Although downspacing from 3 to 4 laterals/pad has a greater impact on increasing the cumulative gas production from optimally-oriented pads than downspacing from 1 to 3 laterals/pad, the lower impact on poorly-oriented pads results in a lower total increase the cumulative gas production from the four pads. At the end of the 25-year production history, 9.0% more gas is recovered for the 4 lateral/pad model than the 3 lateral/pad model, which predicts 1.2× more gas than the 1 lateral/pad model. The recovered shale gas exceeds the recovered coal gas after ~7 years of production. The higher contribution of produced coal gas predicted due to downspacing results from a higher contribution of recovered gas from the main coal seam, while the contribution from the minor coal seams is lower. Downspacing has a minimal impact on the cumulative water production;after 25 years of production a difference of 1.0% is predicted between models with 4 and 3 laterals/pad and 1.7% between models with 1 and 3 laterals/pad. While downspacing increases the cumulative water production for the poorly-oriented pads (1.1× for 3 to 4 laterals/pad and 1.3× for 3 to 1 lateral/pad after 25 years), the cumulative water production for the optimally-oriented pads is lower over the majority of the production history (after ~4 years and 3.2% lower after 25 years for 3 to 4 laterals/pad and after ~6 months and 1.1× lower after 25 years for 1 to 3 laterals/pad).

煤层气SCS系统对Modbus485数据的处理方法设计

提出了基于施耐德系列PLC第三方通讯技术对Modbus485数据处理的控制方案,即在一个平台上实现PCS、ESD和仪表控制系统的控制,该技术已在煤层气SCS系统上得到应用,并在提高数据监控一体化上取得良好效果。

Motion characteristics and density separation of fine coal in an inflatable-inclined liquid-solid fluidized bed

To improve the adaptability of fluidized beds for fine coal separation,a new type of liquid-solid fluidized bed was constructed,i.e.,the inflatable-inclined liquid-solid fluidized bed(IILSFB).A combination of simulation analysis and separation experiments was used to analyze the fluidization characteristics and separation performance of the IILSFB.The results showed that there was upflow and downflow in the fluidized bed.The upflow was mainly composed of water flow,followed by light and heavy particles;on the other hand,the downflow was caused by the backflow of heavy particles that settled at the inclined section.In addition,the light particles that settled at the inclined section could return to the rising water flow under the action of secondary airflow.As the water velocity,separation time,and secondary gas velocity increased,the comprehensive separation efficiency of fine coal in the fluidized bed improved,while the value decreased as the feed quantity increased.This also indicated the order of importance for these four factors,i.e.,water velocity,separation time,feed quantity,and secondary gas velocity,on fluidisation.Furthermore,the comprehensive separation efficiency of 0.1-1 mm fine coal varied significantly with various factors,while that of∼0.1 mm and 1-3 mm fine coal was always at a low value.In the latter case,the classification process of the size fraction was significantly better than the separation process in the fluidized bed.Under optimal working conditions,an IILSFB was used to separate the fine coal(0.1-1 mm).The yield of clean coal was 37.95% with an ash content of 12.11%,and the possible error was 0.085 g/cm^(3),indicating that the IILSFB had good separation performance for 0.1-1 mm fine coal.

超(超)临界燃煤发电技术研究

分析了我国能源需求增长情况,比较分析了整体煤气化联合循环发电(IGCC)技术、加压流化床燃烧(PFBC)技术及超临界、超超临界燃煤发电(SC,USC)等发电技术的经济性和其对环境的影响,得出了在现阶段发展超(超)临界机组可行且必要的结论。介绍了国外已有经验和开展的工作以及国内三大电站设备制造厂超(超)临界锅炉技术的情况,对我国超(超)临界发电技术的应用前景进行了展望。

超临界CO_2在煤层气井压裂技术中的特性研究应用

针对高能气体压裂技术应用于煤层气井中出现产能低的问题,设计了一种新型煤层气井高能气体压裂器实现增产的目标,依据超临界CO2流体性质理论研究了流体压力和温度的关系,结合经验公式计算了膜片破膜压力,确定了超临界CO2流体压力与破膜压力的关系。实验结果表明:在75 g的发热药和1.25 kg的CO2作用下,压裂器产生的峰值压力达到90 MPa,管内最大温度达到453 K,可破厚2 mm膜片。理论分析和实验结果为进一步优化发热药量、CO2量和膜片厚度提供了理论和实验基础,为压裂器设计和工艺优化提供更为精确的技术支撑。