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Due to strong stress sensitivity resulted from unconventional tight formationsit is of practical interest to formulate a reasonable pressure drawdown plan to improve gas extraction recovery. The impact of water-shale interactions ...
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Due to strong stress sensitivity resulted from unconventional tight formationsit is of practical interest to formulate a reasonable pressure drawdown plan to improve gas extraction recovery. The impact of water-shale interactions on the reservoir permeability was previously ignored in the managed pressure drawdown optimization. The controlled-pressure production dynamic analysis was mostly conducted using numerical simulation, lack of rigorous theoretical support. Hence in this paper, a theoretical production prediction model was proposed and verified with HIS RTA 2015by incorporating multiple pressure drawdown mechanisms and various non-linear gas flow process. The on-site production effects dominated by two different pressure drop methods was further compared, indicating that compared to depressurization production, the production reversion can occur in the controlled pressure production process and the EUR of single well can be increased by about 30% under the control of managed pressure drawdown approach. Finally, the pressure drawdown optimization strategy was carried out on the field test from the both production effect and economic benefits, which demonstrated that the best economic solution can generally be obtained in the early stage of production. The research results can be closely linked to the on-site production practice of shale gas wells, providing insights into designing optimized production strategy scheme.
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Geochemical data have been used as the most effective proxies for determining palaeoclimate and palaeoenvironmental conditions. In this article, we conduct a systematic review on a variety of geochemical data of sediments that are...
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Geochemical data have been used as the most effective proxies for determining palaeoclimate and palaeoenvironmental conditions. In this article, we conduct a systematic review on a variety of geochemical data of sediments that are considered proxies for tracing palaeoclimate and palaeoenvironmental information. Comprehensive studies have been carried out on the palaeoproductivity, redox conditions, palaeoclimate, and the acquired data on the enrichment mechanism of organic matter have been summarized. The general mechanisms of the geochemical data regarded as the palaeoclimate and palaeoenvironmental archives include the characteristics of mineral composition, major and trace elements, and rare earth elements. The palaeoproductivity index, including the Ba and P, indicate that the organic-rich shale was deposited in a high-productivity water column. The trace elements revealed that the Longmaxi units recorded variable redox conditions from anoxic to aerobic. The elements V, U, Th, Ni, and Co together with the U/Th, V/Cr, Ni/Co, and V/(V + Ni) are essential indicators for defining the redox conditions. The NASC-normalized REE + Y distribution indicates that the Longmaxi Formation was slightly altered by detrital materials in reduced and acidic environments. The Sr/Cu and MgO/CaO all reveal that the palaeoclimate was gradually transformed from humid to dry heat. The Sr/Ba ratio implies that the water depth fluctuates frequently at the early stage of sedimentation. All geochemical data integrated with the sedimentary characteristics show that anoxic conditions, high palaeoproductivity, and relatively humid palaeoclimates contributed to the accumulation of organic-rich shale. We propose that jointly utilizing various geochemical and sedimentary indices can expand the outlook of the palaeoenvironment and provide a better understanding of the organic matter accumulation mechanisms.
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We herein present a method for predicting adsorption isotherms of methane on shale using the simplified local density (SLD) theory: First, the adsorption isotherms of methane on shale samples were measured and then its adsorption ...
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We herein present a method for predicting adsorption isotherms of methane on shale using the simplified local density (SLD) theory: First, the adsorption isotherms of methane on shale samples were measured and then its adsorption on illite, illite/smectite mixed layer, chlorite, type I, type II and type III kerogen was described with the SLD theory. Second, based on the SLD parameters obtained from adsorption data on kerogen, clay minerals and the composition of the studied shale, we predicted adsorption capacity of the shale using a linear combination of the adsorption capacities of the pure substances weighted by their relative abundance.
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Recent observations of shale gas breakthroughs in the Weiyuan marine shale gas play in the Sichuan Basin have attracted great interest. To better understand these breakthroughs, we have used core description, cyrofocused ion beam ...
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Recent observations of shale gas breakthroughs in the Weiyuan marine shale gas play in the Sichuan Basin have attracted great interest. To better understand these breakthroughs, we have used core description, cyrofocused ion beam scanning electron microscopy data, X-ray diffraction data, organic geochemistry, and welllogging data to better understand the reservoir characteristics carbonaceous shale, calcareous shale, and siliceous shale lithology, with a focus on organic-rich shale units. We find that conventional well-log methods are effective in mapping the spatial distribution of organic-rich shale in the Weiyuan area where the total organic carbon (TOC) content in the Longmaxi Formation ranges from 1.35% to 6.95%, averaging 4.42%. The kerogen is type I-II, and the vitrinite reflectance (Ro) is greater than 2.57%, which indicates that the formation is susceptible to shale gas accumulation. The clay mineral content ranges from 48 to 63 wt% (avg. 51 wt%) with illite and chlorite averaging 73.8% and 25.7%, respectively. The brittle mineral quartz and plagioclase content ranges from 32 to 61 wt% (avg. 47 wt%). Compared to the surrounding lithologic units, the marine shale exhibits relatively high gamma ray, neutron, sonic, resistivity, potassium, and uranium (U) values and relatively low density, photoelectric effect, and thorium/U values, allowing us to construct crossplots to define the units of interest. Using the same process, we quantify the TOC content providing a spatial distribution of organic-rich shale using conventional well logging.
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Predicting the production behaviors of shale gas wells is of great importance for further developing future unconventional hydrocarbon strategies. An accurate prediction production, as well as reliable shale gas production models,...
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Predicting the production behaviors of shale gas wells is of great importance for further developing future unconventional hydrocarbon strategies. An accurate prediction production, as well as reliable shale gas production models, are required to fully understand the shale gas exploitation budget. However, a major problem with classical analytic methods is the insufficient accuracy of the existing models, the time-consuming collection of historical production data, and the costly computational expense. To minimize this problem, a combination of the exponential smoothing method, autoregressive integrated moving average (ARIMA) model, and long short-term memory (LSTM) model was proposed to provide robust support for the production behaviors of shale gas. In this paper, we employed shale gas well production data to establish a database for model training and optimized the predicted model. Hereby, we sought to evaluate the production data predicted by conventional analytical methods, the exponential smoothing method, the ARIMA model, and the LSTM model. Shortly afterward, we objectively compared the predicted results obtained by the novel LSTM model and traditional analytical methods, such as Arps, stretched exponential decline (SEPD), and the Duong model. Herein, we compared the computational cost between the LSTM model and traditional numerical simulation. The combined interpretation of the proposed model demonstrates that the LSTM model achieved scientific accuracy and outstanding results in both short-term and long-term predictions, and realized production prediction of the adjacent well, with excellent agreement with the real shale gas production and a low error, making it an effective tool in forecasting shale gas production. This assay could be used as a potential approach for evaluating deep learning in the petroleum industry and for predicting the future production of unconventional hydrocarbons.
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A large proportion of shale gas is in adsorbed state. However, in the process of shale gas development, adsorbed gas in the shale pores will gradually desorb, which results in the permeability change of shale. This study aims to f...
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A large proportion of shale gas is in adsorbed state. However, in the process of shale gas development, adsorbed gas in the shale pores will gradually desorb, which results in the permeability change of shale. This study aims to find out the adsorption and desorption characteristics of shale and whether there exists certain impact of desorption effects on shale permeability by experiments. Isothermal adsorption and desorption curves of shale gas are not coincident and the desorption curves are in hysteresis. Langmuir equation can be used to calculate the shale isothermal adsorption curve and desorption equation can be used to calculate the shale gas isothermal desorption curve. The permeability of shale was measured, respectively, under low pressure and high pressure, with methane and helium as experimental gas. Then, the comparison was made between the results of shale and the similar experiment results of tight gas sandstone. The results are showed as follows: adsorption effects will break the linear relationship between the shale permeability and the reciprocal of average pore pressure under low pressure; under high pressure, when gas desorption enhances, shale permeability significantly increases. Therefore, adsorption effects can impact the shale permeability under low pressure as well as under high pressure, which should be taken into consideration in the shale gas development.
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To understand methane adsorption characteristics on shale at high pressures, we conducted experiments of methane adsorption on dry shale up to 50MPa and at 95.6 degrees C, 75.6 degrees C, and 40.6 degrees C. Results show that the ...
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To understand methane adsorption characteristics on shale at high pressures, we conducted experiments of methane adsorption on dry shale up to 50MPa and at 95.6 degrees C, 75.6 degrees C, and 40.6 degrees C. Results show that the amount of excess adsorption on shale at high pressures is not the same as that at low pressures. The amount of adsorption increases with pressure until a peak value is reached and then declines with further pressure increases. Isosteric heat of adsorption is studied to explain the excess adsorption behavior. In addition, a new supercritical adsorption model was developed based on supercritical adsorption. This new model and Langmuir model were both used to fit the adsorption isotherms data. Langmuir model matched well with experiment data only at low pressures but failed at high pressures. The new model can fit the adsorption isotherms well, indicating that it reflects the characteristics of supercritical methane adsorption on shale at high pressure and temperature.
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The established literature demonstrates the critical role of the policy mix in the formulation and implementation of government policies for industrial upgrading. However, existing studies mainly examine the policy mix from either...
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The established literature demonstrates the critical role of the policy mix in the formulation and implementation of government policies for industrial upgrading. However, existing studies mainly examine the policy mix from either a horizontal or a vertical coordination perspective; very few examine both dimensions. To gain further insights, the current study involves an analysis of how China's central government manages horizontal and vertical coordination to pursue upgrading in manufacturing industries on the basis of an ambidextrous policy mix perspective and a thorough examination of both the external attributes (i.e., policy level) and content (i.e., policy instruments and themes) of policy documents. This analysis reveals several viable policy implications in relation to China's manufacturing transformation. In particular, it finds that China's policy mix for achieving manufacturing upgrading is highly coordinated on both horizontal and vertical dimensions. Governments at all levels apply the same set of policy instruments; environmental instruments are the most frequently used, followed by supply- and demand-side instruments. The core policy topics within the manufacturing upgrading structure include innovation, industrial transformation, industrial agglomeration, demonstration projects and service-oriented manufacturing. Therefore, this study establishes recommendations for future policies, which should focus on reinforcing guidance regarding national policies, encouraging local governments to apply innovative policy tools and increasing the use of demand-side policy instruments.
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Pore characteristics are one of the most important elements in the study of shale reservoir properties and are a key parameter for the evaluation of the potential of shale oil and gas resources. Low-temperature nitrogen adsorption...
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Pore characteristics are one of the most important elements in the study of shale reservoir properties and are a key parameter for the evaluation of the potential of shale oil and gas resources. Low-temperature nitrogen adsorption is a common laboratory method that is used to characterize the pore structure of shale. However, the effect of shale’s particle size on the experimental results of the nitrogen adsorption of deep shale samples is still unclear. In this paper, using deep shale samples of different mesh sizes from the Luzhou Block as an example, we studied the effect of particle size on the pore structure of deep shale, as characterized by nitrogen adsorption experiments. The results showed that the pore volume of deep shale is mainly distributed in the mesoporous range, with a pore size ranging from 2 to 20 nm. The pore volume, as measured by nitrogen adsorption, increases slowly as the particle size decreases and then it increases rapidly. The particle size of shale has no obvious effect on the measurement of the specific surface area. The fractal dimension of deep shale gradually increases as the particle size of the shale samples increases and the smaller the particle size, the higher the correlation coefficient, R2, of the fractal dimension fitting. In this paper, different recommended sizes are given for selecting suitable particle sizes in nitrogen adsorption experiments on deep shale with different structural parameters, which will increase the accuracy of the study of the pore structure of deep shale.
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Internet of Things (IoT) and Big Data technologies are becoming increasingly significant parts of national defense and the military, as well as in the civilian usage. The proper deployment of large-scale wireless sensor network (W...
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Internet of Things (IoT) and Big Data technologies are becoming increasingly significant parts of national defense and the military, as well as in the civilian usage. The proper deployment of large-scale wireless sensor network (WSN) provides the foundation for these advanced technologies. Based on the Fruchterman–Reingold graph layout, we propose the Fruchterman–Reingold Hexagon (FR-HEX) algorithm for the deployment of WSNs. By allocating edges of hexagonal topology to sensor nodes, the network forms hexagonal network topology. A comprehensive evaluation of 50 simulations is conducted, which utilizes three evaluation metrics average moving distance, pair correlation diversion (PCD), and system coverage rate. The FR-HEX algorithm performs consistently, the WSN topologies are properly regulated, the PCD values are below 0.05, and the WSN system coverage rate reaches 94%. Simulations involving obstacles and failed nodes are carried out to explore the practical applicability of the FR-HEX algorithm. In general, the FR-HEX algorithm can take full advantage of sensors’ hardware capabilities in the deployment. It may be a viable option for some IoT and Big Data applications in the near future.
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