Continuous Gas Production Research Articles

Distance-Based Fluorescent Immunosensor for Point-of-Care Test of Illegal Additives through the Gas-Producing Nanozyme.

The colorimetric point-of-care test (POCT) offers a rapid and efficient method for detecting specific targets in real samples. However, traditional colorimetric methods often rely on complex signal amplification techniques or electronic devices to enhance detection sensitivity, which can inadvertently increase both cost and time, thus contradicting the fundamental goals of visual detection methods. Here, we presented a distance-based fluorescent immunosensor that utilized a gas-producing nanozyme for continuous gas production reaction as a signal. Specifically, the SOM-ZIF-8@Pt nanozyme catalyzed the production of O2 from H2O2 to cause an obvious increase in the pressure within a sealed chamber, thus driving the production of H2S to quench the fluorescence of CsPbBr3 on the walls of the capillaries. Based on the competitive immunoassay, the fluorescence quenching lengths were relative with the concentration of aminopyrine in the range from 0.2 to 20 ng/L; thus, the fluorescent POCT-based homemade device was realized through the amplification of distance-based signals facilitated by the continuous gas production reaction. This strategy provides an effective way to realize POCT assays in resource-limited areas by transforming pressure variations into directly observable signals. Furthermore, distinguished by its high sensitivity, ease of operation, and portability, it also represents a significant advancement in biomedical diagnostics, particularly within home healthcare and clinical POCT.

Overcoming equilibrium constraints in the reverse water gas shift with counter-current gas–solid flow and oxygen transport in La0.75Sr0.25Cr0.5Mn0.5O3-δ

Utilizing carbon dioxide in the reverse water gas shift (RWGS) reaction (CO2+H2→CO+H2O) is a potential pathway for mitigating CO2 emissions, as the resulting CO can be used to produce valuable products, such as chemicals and fuels. Here, we explore the implementation of the RWGS reaction by solid-oxide redox cycling in a two-reactor moving-bed process with counter-current gas–solid flow. We also develop a method for obtaining design diagrams from the thermodynamic data of the solid oxide utilized for redox cycling. Using this tool and screening the previous literature for relevant thermodynamic data, we identify the perovskite La0.75Sr0.25Mn0.5Cr0.5O3-δ as a highly promising candidate material, and we experimentally determine its non-stoichiometry under conditions relevant for the RWGS. The reaction kinetics are also obtained for its reduction in H2 and its reoxidation in CO2. We observe that the inward diffusion of oxygen into the perovskite grains during reoxidation in CO2 is likely to determine the minimum feasible temperature at which this process can be operated, and we estimate an effective diffusion coefficient of D = 7.7−1.4+1.8 *10−14 cm2 s−1 at T = 550 °C, with an activation energy of 122±4.4 kJ mol−1. Implementing the RWGS with this material in counter-current gas–solid flow is expected to significantly improve the RWGS process by decreasing the operating temperature, enabling continuous gas production, and increasing the gas conversion.

Highly Stable Photocatalytic Dry and Bi-Reforming of Methane with the Role of a Hole Scavenger for Syngas Production over a Defective Co-Doped g-C3N4 Nanotexture

Photocatalytic reduction of CO2 with CH4 through the dry reforming of methane (DRM) is an attractive approach to recycling greenhouse gases into valuable chemicals and fuels; however, this process is quite challenging. Although there is growing interest in designing efficient photocatalysts, they are less stable, and have lower photoactivity when employed for DRM reactions. Herein, we developed a noble metal-free hierarchical graphitic carbon nitride (HC3N4) loaded with cobalt (Co) for highly efficient and stable photocatalytic dry reforming of methane to produce synthesis gases (CO and H2). The performance of the newly designed Co/HC3N4 composite was tested for different reforming systems such as the dry reforming of methane, bi-reforming of methane (BRM) and reforming of CO2 with methanol–water. The performance of HC3N4 was much higher compared to bulk g-C3N4, whereas Co/HC3N4 was found to be promising for higher charge carrier separation and visible light absorption. The yield of CO and H2 with HC3N4 was 1.85- and 1.81-fold higher than when using g-C3N4 due to higher charge carrier separation. The optimized 2% Co/HC3N4 produces CO and H2 at an evolution rate of 555 and 41.2 µmol g−1 h−1, which was 18.28- and 1.74-fold more than using HC3N4 during photocatalytic dry reforming of methane (DRM), with a CH4/CO2 feed ratio of 1.0. This significantly enhanced photocatalytic CO and H2 evolution during DRM was due to efficient charge carrier separation in the presence of Co. The CH4/CO2 feed ratio was further investigated, and a 2:1 ratio was best for CO production. In contrast, the highest H2 was produced with a 1:1 feed ratio due to the competitive adsorption of the reactants over the catalyst surface. The performance of the composite was further investigated for bi-reforming methane and methanol. Using photocatalytic CO2 reduction with CH4/H2O, the production of CO and H2 was reduced, whereas significantly higher CO and H2 evolved using the BRM process involving methanol. Using methanol with CO2 and H2O, 10.77- and 1.39-fold more H2 and CO efficiency was achieved than when using dry reforming of methane. The composite was also very stable for continuous synthesis gas production during DRM in consecutive cycles. Thus, a co-assisted g-C3N4 nanotexture is promising for promoting photocatalytic activity and can be further explored in other solar energy applications.

Comparison of fluid production between excess-gas and excess-water hydrate-bearing sediments under depressurization and its implication on energy recovery

Methane hydrates are considered as the future energy due to its vast resource volume and high energy density. The fluid production and thermal response of two types hydrate-bearing sediments (i.e., excess-gas and excess-water) under controlled depressurization are still unclear and warrant investigation. In this study, we devised two different hydrate-bearing sediments (HBS) synthesis methods and synthesized excess-water (SA = ∼27.2%) and excess-gas (SG = ∼26.5%) HBS with SH of 72.0%. The hydrate dissociation kinetics and fluid production behavior were examined under three bottom-hole pressures, i.e., 3.0, 5.0, and 7.0 MPa. Gas production from the excess-gas HBS follows two-stage profile, while continuous gas production was observed after SG reaches 6.0% in the excess-water HBS. Water production from excess-gas HBS was significantly delayed compared with excess-water HBS and only started when SA reached above 22.5%. A logarithmic water production profile was observed in all cases. Rapid temperature drop due to hydrate dissociation is significantly delayed in excess-gas cases. Heat transfer from surroundings is relatively slow due to its low composite thermal conductivity. The findings on the contrast fluid production behavior between excess-gas and excess-water cases shed light on optimizing production strategies for future field production trials from these two different types reservoirs.

Dynamic tensile mechanical properties of thermally damaged sandstone under impact loads and the influence mechanism of composition

The stability of surrounding rock in the combustion void is the key to continuous, safe, and efficient gas production in an underground coal gasification project. The key factors influencing the stability of surrounding rock in the combustion void are high temperature and impact dynamic load. At the same time, rock structure failure mainly depends on the rock materials’ tensile strength. Therefore, it is fundamental to study the dynamic tensile mechanical properties of thermally damaged rocks to control the surrounding rock stability of the combustion void in UCG projects. This paper used the coal measures as the research object. The dynamic direct tensile test of thermally damaged sandstone was carried out using a high-temperature load system and split Hopkinson tension bar (SHTB) test system. The test results showed that the dynamic tensile strength of sandstone increased linearly with the increase in strain rate. In contrast, it increased first and then decreased with temperature. In addition, the nonlinear regression method was applied to establish the prediction model of dynamic tensile properties of thermally damaged sandstone. XRD analyzed the composition and mass fractions of sandstone. From the standpoint of composition change, the change mechanism of the mechanical properties of thermally damaged coal measured in sandstone was illustrated.

The impact of mineral compositions on hydrate morphology evolution and phase transition hysteresis in natural clayey silts

Natural gas hydrate is a clean and high-efficient energy resource, and more than 90% of its reserves are contained in fine-grained (typically clayey silts) sediment. In this work, for the first time, the micro-scale imaging is performed to explore hydrate phase transition, morphology evolution and fundamental characteristics (mineral compositions, pore structures and seepage capacity) in clayey silt sediments. The results indicate that clayey silts formation properties strongly depend on dominant minerals component in the sediments. The clay-rich clayey silt possesses more microcapillary interstice with smaller permeability than that in quartz-rich sediment. Hydrates generally occur as microfracture-filling (veins) and grain-displacing (nodulus) in sand-rich clayey silt. While they occur in the form of fracture-filling (vein) and foraminifera-filling in clay-rich clayey silt sediments. Biological fossils (especially foraminifera) provides potential space for hydrate aggregates. But hydrate formed inside it depends on the structures of fossils, the mineral components and pore structure of surrounding matrix. The hysteresis between hydrate formation and decomposition found to be more significant in clay-rich clayey silt sediment than quartz-rich sediment. And this hysteresis inside foraminifera is much more serious compared with that in matrix. In addition, dispersed pore-filling hydrates forms during decomposition, which has adverse effect on continuous gas production.

The void fraction and frictional pressure drop of upward two-phase flow under high pressure brine condition

The offshore methane hydrate production test conducted in Japan has demonstrated a successful production of methane gas from marine gas hydrates using depressurization methods. The method produces methane gas by dissociating methane hydrate, which is stable at low temperature and high pressure conditions, by lowering the bottom-hole pressure in the wellbore. Under this method, stable control of bottom-hole pressure is necessary to ensure continuous methane gas production. Therefore, understanding the behavior of upward gas–liquid two-phase flow, involving gas-brine mixture, in a wellbore is essential for the proper pressure drop evaluation in the production line. In the present study, void fraction and frictional pressure drop behaviors under nitrogen-brine two-phase flow conditions is investigated using the high-pressure test facility of 52.7 mm inner diameter and 28 m height. The measured void fraction was assessed using drift-flux model, and the results showed that the decrease in bubble diameter under bubbly flow in gas-brine two-phase flow conditions resulted in decrease in bubble rise velocity and uniformity of bubble distribution. It was also found that, under bubbly flow in gas-brine mixture, the frictional pressure drop tends to further decrease with elevation. Based on these findings and obtained experimental dataset, the new frictional pressure model for gas-brine two-phase flow under high-pressure conditions is developed in the present study.

Numerical simulation on the evolution of physical and mechanical characteristics of natural gas hydrate reservoir during depressurization production

Changes in the physical and mechanical characteristics of the natural gas hydrate reservoir during depressurization production can affect safe and efficient production. In order to reveal the evolution law of reservoir physical and mechanical characteristics, based on the establishment of thermo-hydro-mechanical-chemical (THMC) multi-field coupling theoretical model, taking SH2 drilling platform in Shenhu sea area of the South China Sea as an example, COMSOL multiphysics is used to simulate the processes of depressurization production with a single horizontal well. The results show that, after the bottom hole pressure began to decrease, the gas and water production rates immediately increased from zero to their respective peaks, and then decreased rapidly. The decomposition of hydrate is an endothermic process. The changes of temperature and pressure conditions have a significant impact on the decomposition of hydrate. Effective stress and Mises stress appear to be concentrated in the area of complete hydrate decomposition. Mises stress rises sharply at the location of the leading edge of decomposition, which needs to be alert to the risk of landslide. In the process of depressurization production, the top of the reservoir gradually appears settlement behavior. The upper area of the horizontal well has a large amount of subsidence, and reservoir modification can be implemented during production to improve the mechanical stability of the reservoir. The results are an important guide to achieve stable and continuous gas production.

Primary studies on the effect of coal bio-gasification in situ in the Qinshui basin

AbstractCoal bio-gasification is one in situ coal gasification technology that utilizes the digestion of organic components in coal by methanogenic bacteria. It is not only an effective technology to enhance the recoverable reserves of coalbed methane, but also an important technical method to promote clean coal utilization. Relevant laboratory researches have confirmed the technical feasibility of anthracite bio-gasification. However, in the complex environment of coal bed, whether in situ gas can be yield with methanogenic bacteria needs to be verified by in situ experiments. In this study, a vertical well and a horizontal well were used in Qinshui basin to perform field experiments to confirm the technical industrial feasibility. The concentration of Cl− ion and number changes of Methanogen spp. were used to trace nutrition diffusion. Gas production changes and coalbed biome evolution were used to analyze technical implementation results. The trace data and biome evolution identified that: (1) The development of Methanoculleus spp. has a significant positive correlation with culture medium diffusion; (2) the structure of coalbed microbial community was significantly changed with the injection of nutrition, and the newly constructed methanogenic community was more suitable for fermentation of coal; and (3) the evolution of dominant microflora has further enhanced bio-gasification of coal. Gas production data showed that the gasification of coal lasted 635 and 799 days and yielded 74,817 m3 and 251,754 m3 coalbed methane in Z-159 and Z-7H wells, respectively. One nutrition injection in coalbed achieved an average of 717 days of continuous gas production in experimental wells. Results confirmed that coalbed methane enhancement with bio-gasification of coal is a potential technology to achieve the productivity improvement of coalbed methane wells. And the findings of this study can help to further understand the mechanism of in situ coal bio-gasification and provide theoretical support for the development of biomining of coal.

Experimental Study on Biogas Digester Combined with Solar Heating System

In order to solve the problem of low gas production of biogas digester fermented at natural temperature in winter and possibly freezing biogas digester in northern cold areas, the biogas digester combined with solar heating system is proposed to maintain the normal fermentation temperature of biogas digester and ensure the continuous and efficient gas production of biogas digester throughout the year. Through the experiment and analysis of the system, in cold area, the temperature of biogas digester can be maintained above 12.5 °C, which can meet the temperature requirements of normal fermentation in biogas digester, so it is concluded that developing solar heating biogas digester project is feasible in cold area.

Computational Fluid Dynamics (CFD) for Modelling Multiphase Flow in Hilly-Terrain Pipelines

The design and operation of subsea pipelines over the life-cycle of an asset is vital for continuous oil and gas production. Qualitative design and effective production operation of pipelines depend on fluid type(s) involved in the flow; and in the case of multiphase flow, the need to understand the behaviour of the fluids becomes more imperative. This work presented in this report is borne out of the need for more accurate ways of predicting multiphase flow parameters in subsea pipelines with hilly-terrain profiles by better understanding their flow behaviors. To this end, Computational Fluid Dynamics has been used as against existing experimental and mechanistic methods which have inherent shortcomings. The results showed that multiphase flow parameters including flow-regimes, liquid hold-up and pressure drop in hilly-terrain pipelines can be modelled without associated errors in existing techniques. Similarity in trend was found when results of pressure gradient in downward-incline pipe were compared with results from existing correlations and mechanistic method. CFD can be used as a design tool and also a research tool into the understanding of the complexities of multiphase flow in hilly-terrain pipelines towards qualitative design and effective operation of hilly-terrain pipelines.

The second natural gas hydrate production test in the South China Sea

Clayey silt reservoirs bearing natural gas hydrates (NGH) are considered to be the hydrate-bearing reservoirs that boast the highest reserves but tend to be the most difficult to exploit. They are proved to be exploitable by the first NGH production test conducted in the South China Sea in 2017. Based on the understanding of the first production test, the China Geological Survey determined the optimal target NGH reservoirs for production test and conducted a detailed assessment, numerical and experimental simulation, and onshore testing of the reservoirs. After that, it conducted the second offshore NGH production test in 1225 m deep Shenhu Area, South China Sea (also referred to as the second production test) from October 2019 to April 2020. During the second production test, a series of technical challenges of drilling horizontal wells in shallow soft strata in deep sea were met, including wellhead stability, directional drilling of a horizontal well, reservoir stimulation and sand control, and accurate depressurization. As a result, 30 days of continuous gas production was achieved, with a cumulative gas production of 86.14 ×10⁴ m³. Thus, the average daily gas production is 2.87 ×10⁴ m³, which is 5.57 times as much as that obtained in the first production test. Therefore, both the cumulative gas production and the daily gas production were highly improved compared to the first production test. As indicated by the monitoring results of the second production test, there was no anomaly in methane content in the seafloor, seawater, and atmosphere throughout the whole production test. This successful production test further indicates that safe and effective NGH exploitation is feasible in clayey silt NGH reservoirs. The industrialization of hydrates consists of five stages in general, namely theoretical research and simulation experiments, exploratory production test, experimental production test, productive production test, and commercial production. The second production test serves as an important step from the exploratory production test to experimental production test.

Gas production behavior from hydrate-bearing fine natural sediments through optimized step-wise depressurization

There have been several field tests around the world to recover natural gas from gas hydrate reservoirs, yet they mostly suffer from the low productivity, sand problems and poor economic efficiency. The ultralow permeability of the sediments and an insufficient heat supply act as major barriers. Intense investigations have been carried out to study the gas production behavior from lab-synthesized hydrate-bearing coarse sands; yet the porous matrices could differ significantly from the natural sediments. Few studies have been found to focus on the role of fine natural sediments in the gas recovery performance. In this study, natural marine sediments from the South China Sea are used as the porous matrices, and gas is produced through an optimized stepwise depressurization. Significant differences in the gas production behaviors from fine natural sediments and coarse grains are found. The fine marine sediments may induce the blockage of the production well, even with protection measures; this problem will result in an uncontrolled pressure drop and gas output. Moreover, the stepwise depressurization efficiently contributes to remitting the temperature drop of the reservoir, increasing the minimum temperature from −0.5 ℃ upon a straight pressure drop to 0.27 ℃ upon a step-wise depressurization. This method can therefore help prevent the ice generation during hydrate dissociation. Additionally, a finer pressure gradient of 0.5 MPa will enhance the hydrate dissociation rate by 18.92% compared with the 2 MPa step scenario. The average gas production rate is determined to positively correlate with the Stefan number, which indicates a dominant role of the sensible heat of the reservoir in the efficient gas production. The findings could be applied in the field tests of gas hydrates to avoid ice generation and achieve a stable and continuous gas production behavior.

Effect of wellbore design on the production behaviour of methane hydrate-bearing sediments induced by depressurization

Methane hydrates have been considered as the future clean energy resource. To recover energy from hydrate-bearing sediments safely and effectively requires a fundamental understanding of the dynamic behaviour of hydrates in sandy media. Past field production tests have proved the technical feasibility of gas production from hydrate reservoirs. However, technical challenges (e.g. sand production and excessive water production) remain in realizing long-term economic-viable production. In this study, we investigate the effect of various wellbore designs (specifically the shape and the location of perforations) on the fluid production behaviour in aqueous-rich hydrate-bearing sediments. Slotted-liner design was first-time incorporated in depressurization under different bottom-hole pressures (2.5 MPa, 3.0 MPa and 4.0 MPa). Continuous gas production and step-wise water production during the early stage of depressurization were observed at all pressures because of the change of fluid flow path from reservoir to wellbore. Compared with traditional borehole design, slotted-liner design showed advantage in controlling water production under low BHP (2.5 MPa). Using wellbores with different perforation locations, it was observed that perforation location does not pose a significant impact on the behaviour of gas production; whereas, middle perforation away from the aqueous-rich and hydrate-rich region yielded the least water production. The experimental results from this study demonstrated the possibility of employing slotted-liner well and varying the perforation location in reducing water production from methane hydrate-bearing sediments. Our findings can pave way for the testing of novel wellbore designs to further enhance gas recovery and reduce water production from hydrate reservoirs.

Comparison of degradation behaviour and osseointegration of the two magnesium scaffolds, LAE442 and La2, in vivo

Porous magnesium implants have been investigated for some time for their orthopaedic applicability as resorbable bone substitutes. The objective of this study was to evaluate the in vivo degradation behaviour and osseointegration of open-pored scaffolds made of the two magnesium alloys, LAE442 (n = 40) and Mg-La2 (n = 40). Cylindrical magnesium scaffolds (diameter 4 mm, length 5 mm) with defined interconnecting pore structure were produced by investment casting and coated with MgF2. Commercially available porous ß-tricalcium phosphate scaffolds (TCP, n = 40) of the same dimensions served as control. The scaffolds were inserted in the cancellous part of the greater trochanter of both femurs in rabbits and evaluated over a period of 36 weeks using regular clinical, radiological and in vivo µCT examinations. No clinical adverse reactions were observed in any of the scaffolds. The X-ray and µCT image evaluation of La2 showed fast and inhomogeneous degradation behaviour with increased gas formation and a rapid loss of scaffold structure and shape from week 12 on. In comparison, the LAE442 scaffolds showed a slow, homogeneous degradation with low but continuous gas production over the entire study period. Furthermore, LAE442 scaffolds showed comparatively better osseointegration with more trabecular contacts than La2 scaffolds and retained their original scaffold structure. Although the TCP control group demonstrated the best osseointegration, it showed overly-rapid degradation. Based on the results of this study, the LAE422 scaffolds have promising properties for further investigations in weight-bearing bone defects.

Advances of experimental study on gas production from synthetic hydrate reservoir in China

China has entered the area of new normal economy which requires the harmonious development of energy consumption, environmental protection and economic development. Natural gas hydrate is a potential clean energy with tremendous reserve in China. The successful field test of marine hydrate exploitation in South China Sea created a new record of the longest continuous gas production from natural gas hydrate. However, the corresponding fundamental research is still urgently needed in order to narrow the gap between field test and commercial production. This paper reviewed the latest advances of experimental study on gas production from hydrate reservoir in China. The experimental apparatus for investigating the performance of hydrate dissociation in China has developed from one dimensional to two dimensional and three dimensional. In addition, well configuration developed from one tube to complicated multi-well networks to satisfy the demand of different production models. Besides, diverse testing methods have been established. The reviewed papers preliminary discussed the mechanical properties and the sediment deformation situation during the process of hydrate dissociation. However, most reported articles only consider the physical factor, the coupled mechanism of physical and chemical factor for the mechanical properties of the sediment and the sand production problem should be studied further.

An in-vitro upper gut simulator for assessing continuous gas production: A proof-of-concept using milk digestion

Using gases as biomarkers is receiving increasing attention across the field of gut health. The use of in-vitro digestion systems that measure gas is common to understand some of the complex systems that create these gases and previously have been conducted using long time period sampling schemes which miss important signatures regarding the dynamics of gas production. Here the development of a mono-compartment in-vitro digestion simulator capable of recording vital dynamic information in real-time including: CO2 concentration; high sensitivity H2 concentration; and pH are presented and validated utilising milk. The impact of a simplified bacterial model, bacterial population size and the presence of lactase are investigated. The favourable gas production outcomes are obtained when lactase is present, at 106 CFU of bacteria, in good agreement with clinical observations. This proof-of-concept system demonstrates reliable and repeatable results and has the potential to enhance the information capacity of current and future in-vitro simulators.

Distribution of gas hydrate reservoir in the first production test region of the Shenhu area, South China Sea

ABSTRACT In May and July of 2017, China Geological Survey (CGS), and Guangzhou Marine Geological Survey (GMGS) carried out a production test of gas hydrate in the Shenhu area of the South China Sea and acquired a breakthrough of two months continuous gas production and nearly 3.1 × 105 m3 of production. The gas hydrate reservoir in the Shenhu area of China, is mainly composed of fine-grained clay silt with low permeability, and very difficult for exploitation, which is very different from those discovered in the USA, and Canada (both are conglomerate), Japan (generally coarse sand) and India (fracture-filled gas hydrate). Based on 3D seismic data preserved-amplitude processing and fine imaging, combined with logging-while-drilling (LWD) and core analysis data, this paper discusses the identification and reservoir characterization of gas hydrate orebodies in the Shenhu production test area. We also describe the distribution characteristics of the gas hydrate deposits and provided reliable data support for the optimization of the production well location. Through BSR feature recognition, seismic attribute analysis, model based seismic inversion and gas hydrate reservoir characterization, this paper describes two relatively independent gas hydrate orebodies in the Shenhu area, which are distributed in the north-south strip and tend to be thicker in the middle and thinner at the edge. The effective thickness of one orebody is bigger but the distribution area is relatively small. The model calculation results show that the distribution area of the gas hydrate orebody controlled by W18/W19 is about 11.24 km2, with an average thickness of 19 m and a maximum thickness of 39 m, and the distribution area of the gas hydrate orebody controlled by W11/W17 is about 6.42 km2, with an average thickness of 26 m and a maximum thickness of 90 m.

The gas isotope interpretation tool: A novel method to better predict production decline

Production decline prediction is important to understand the performance and life span of oil and gas wells. The most common prediction method is decline curve fitting based on available production rate data. Such data are fit with different equations that extrapolate to future time. However, the parameters are commonly poorly constrained, especially when the production rate data are limited. In this study, we establish a novel gas isotope interpretation tool to better predict the resource quantity and life span of producing gas wells. This tool is based on the evolution of methane carbon isotope ratios (δ13C1) caused by different gas-releasing processes during production. It requires (1) real-time methane carbon isotope ratio data, (2) continuous gas production rate data for a certain period of time, and (3) basic geological and engineering conditions. We successfully applied the production decline prediction tool to a producing shale gas well in the Barnett Shale. We obtained real-time δ13C1 data for approximately 1 yr using our proprietary, field-deployable gas chromatography–infrared isotope ratio analyzer. The prediction in this well from the isotope method showed a total reserve of up to 7.34–7.75 BCF (2.07–2.19 × 108 m3), which was used to constrain the production decline trend of the study well. The measured production rate data were first fit using the Arps equation, which then joined to an exponential decline curve smoothly at approximately 10 yr, such that the cumulative production calculation from integration of the product rate curve equaled to the total reserve predicted by the isotope method. The novel production decline prediction method thus provided important constraint on the future well production and expected ultimate recoverable reserves.

Erweiterung der Flexibilität von Biogasanlagen – Substratmanagement, Fahrplansynthese und ökonomische Bewertung

Since the amendment of the German Renewable Energy Act (EEG) in 2012 as well as in the current version (EEG 2014) the parameters for the expansion of renewable energies aim for a stronger market integration of those. Thereby, biogas plants represent a promising option to produce demand-driven energy to compensate differences between energy demand and energy supply caused by irregular sources (e. g. wind and solar). The contribution focuses on the economic assessment of the flexible biogas production by specific feeding in comparison to continuous gas production against the background of a flexible conversion of biogas into electrical power. The required additional demand for gas storage capacity of a model biogas plant is determined by combinations of different feeding regimes and by three optimised power generation schedules. Subsequently, a cost-benefit analysis is conducted to assess the substrate management economically. The developed methodology is especially designed for existing plants and is used for assessing a multi-factorial substrate management as flexibility option. The results show that substrate management is increasingly appropriate to reduce the additional demand for gas storage especially for longer-term planning horizons (above 12 h) regarding schedule organisation. Moreover, the flexible operation allows generating higher marketing revenues on the European Power Exchange (EPEX Spot SE) at low additional costs.