Search

The aim of the research is to determine changes in the composition of selected gasoline compounds in cotton carpet samples due to different weathering times. EVO 95 gasoline was used as a fire accelerant and a cotton carpet was used as a matrix. The samples were exposed to various weathering durations (0–360 min) in laboratory conditions. We investigated samples that were unburnt (only weathered) and samples that were burned and subsequently subjected to further weathering. Residual gasoline compounds in carpet samples were determined by gas phase extraction (headspace – HS) coupled with gas chromatography (GC) and mass spectrometry (MS). We focused on the comparison of selected gasoline compounds; toluene, ethylbenzene, p-xylene, 1,2,3-trimethylbenzene (TMB), 1,3,5-trimethylbenzene and naphthalene. The biggest changes were determined in the reduction of the intensity of most volatile compounds (alkylalkanes), where toluene decreased by 11.92%. A similar but not so pronounced trend, occurred in the burned samples, where toluene decreased by 7.40%. Minor changes occurred in alkyl derivatives of benzene, where some of the total 15 gasoline markers also occur, e.g. (1,2,3-trimethylbenzene, 1,3,5-trimethylbenzene). On the contrary, naphthalene as a heavier compound showed an increase in intensity about 0.42%. For burnt samples, the increase was 1.31%. The results show that largest changes can be observed after four or five hours of weathering, which implies the need for rapid sampling and subsequent timely analysis. [ABSTRACT FROM AUTHOR]

Coal (Rock) pillar retaining in the mining of protective layer would cause gas dynamic disaster in the protected layer. Based on the gas geological conditions of the two-layer coal seam in Jinhe Coal Mine of Yaojie Mining District, the stress evolution law of coal seam in the rock pillar affected area was studied by theoretical analysis and numerical simulation, and the crack development law of coal seam in different loading stages under conventional triaxial loading was studied by CT scanning technology. With the analysis of the stress evolution and crack development of coal in rock pillar affected area, the gas extraction effect under different stress states and the gas desorption law after pressure relief antireflection were studied on site. The results showed that the stress of coal in the rock pillar affected area is in the approximate elastic stage of the conventional triaxial stress-strain curve, and the cracks of coal are mainly closed at this stage. Meanwhile, the increase of stress leaded to the decrease of coal permeability and the poor gas extraction effect. CT scanning tests under conventional triaxial loading were carried out in the laboratory, and three-dimensional visual models of coal sample cracks were constructed at different loading stages. When loading to the linear elastic stage, the crack volume and surface area were reduced by 74% and 71% compared with the ones in initial state. At the same time, the expression between stress σ and crack density T was further established. After comprehensive control measures such as intensive drilling discharge, presplitting blasting and coal water injection were taken to the coal in rock pillar affected area, the crack density T could reach the crack development level of the conventional triaxial loading softening stage, realizing the crack development of the coal under low stress. The enclosed gas in front of the coal could desorption flow during the roadway driving. And the predict index value K1 also decreased from 0.57 mL/(g·min1/2) to 0.17 mL/(g·min1/2) continuously. The safety of coal roadway in rock pillar affected area was realized, and the accuracy of numerical simulation and laboratory test results was verified, which had certain reference significance for coal roadway excavation under this similar conditions. [ABSTRACT FROM AUTHOR]

The controlled shock wave (CSW) fracturing is an effective method for enhancing permeability of coal seam to promote gas extraction. Based on Fick’s law, Darcy’s law, the ideal gas law and the Langmuir equation, a damage-seepage-deformation coupling mathematical model of CSW fracturing in coal seam combined with the maximum tensile stress and the Mohr-Coulomb criterion is established. This model is implemented into COMSOL Multiphysics to simulate the coal seam CSW fracturing and subsequent gas extraction. When the shock wave and isotropic in-situ stress are applied on the borehole wall, the coal damage zone is an annular shape, and the permeability in the damage zone increases sharply. The CSW can effectively increase the efficiency of gas extraction and reduce the gas pressure and gas content in coal seam. With the increase of CSW action times, the damage in coal mass reaches a threshold and tends to be stable after several shocks. The damage area and the gas extraction efficiency are positively correlated with the shock intensity. Under the anisotropic ground stress, the larger diversity of the stress in different directions is, the more obvious damage extension in the fractured coal along the maximum stress direction is. Ground stress can inhibit the extension of cracks in the CSW fractured coal seam. This inhibition effect becomes more obvious with the increase of in-situ stress. Parameters are substantiated of controlled shock wave impact on the coal seam, which ensures increased methane extraction from low-permeability reservoirs, are substantiated. [ABSTRACT FROM AUTHOR]

Gas extraction drilling is a necessary measure for managing gas hazards. For soft coal seams where gas extraction drilling holes are prone to collapse, it is believed that drill rod disturbance is the main cause of hole collapse. This study proposes a research approach to reduce wall stress by optimizing the drill rod structure. Through theoretical analysis, numerical simulation, and industrial tests, a stress model for the drill rod inside the hole was established, and a wall stress equation was derived. The effects of various parameters on wall stress were analyzed. The study suggests optimizing the drill rod structure to reduce the disturbance‐induced wall stress. SolidWorks was used for drilling stress simulation, and a four‐winged concave groove drill rod was developed. After strength verification, comparative industrial tests were conducted. The research results show that as the line density increases, the wall stress of the drilling hole increases. As the length of the suspended section increases, the wall stress initially decreases and then increases. With increasing drilling thrust, wall stress increases linearly, and the growth rate is greater with a larger diameter difference between the drill hole and the drill rod. Numerical simulation results indicate that the critical point maximum stress at the hole entrance, the critical point maximum stress at the hole bottom, and the average stress at the bottom section of the four‐winged concave groove drill rod with a concavity of 5 are significantly reduced compared to those of circular and grooved drill rods. Industrial test results show that using the four‐winged concave groove drill rod significantly reduces the extent of hole collapse. This study provides a reference for addressing the issue of hole collapse in gas extraction drilling for soft coal seams. [ABSTRACT FROM AUTHOR]

To study the effect of coal pressure on gas extraction under fluid‐solid coupling, the effect of gas extraction radius under different pore sizes and treatment methods was simulated by using COMSOL Multiphysics software, the time evolution law of gas pressure on coal surface was obtained, and the numerical simulation results were verified by the observation of flow rate and concentration in experimental mine combined with fluid‐solid interaction. The results show that the distance of extraction radius increases with the increase of borehole diameter, and the relation between extraction time and extraction radius is a power function, but the increase gets smaller and smaller until it becomes zero. For Φ98 mm borehole and Φ120 mm borehole, hydraulic treatment can increase the efficiency of gas extraction by 31.3% and 22.7%, respectively. For hydraulic treatment and conventional treatment, the ratio of gas drainage effect by enlarging hole size is 6.3% and 13.8% respectively. Compared with the areas without gas extraction under the four conditions, the descending speed of gas pressure from fast to slow is Φ120 mm hydraulic flushing treatment, Φ98 mm hydraulic flushing treatment, Φ120 mm conventional treatment, Φ98 mm conventional treatment. Compared with four different conditions, after 180 days of extraction the coal gas pressure decreased by 75.3% within reasonable hole spacing. At the same time, in multi‐hole pumping, the influence area of adjacent borehole is larger than that of single‐hole pumping, and the spacing of borehole should be less than twice the radius of pumping. [ABSTRACT FROM AUTHOR]

In the contemporary era, the further exploitation of deep-sea resources has led to a significant expansion of the role of ships in numerous domains, such as in oil and gas extraction. However, the harsh marine environments to which ships are frequently subjected can result in structural failures. In order to ensure the safety of the crew and the ship, and to reduce the costs associated with such failures, it is imperative to utilise a structural health monitoring (SHM) system to monitor the ship in real time. Displacement reconstruction is one of the main objectives of SHM, and the inverse finite element method (iFEM) is a powerful SHM method for the full-field displacement reconstruction of plate and shell structures. However, existing inverse shell elements applied to curved shell structures with irregular geometry or large curvature may result in element distortion. This paper proposes a high-precision iFEM for curved shell structures that does not alter the displacement mode of the element or increase the mesh and node quantities. In reality, it just modifies the methods of calculation. This method is based on the establishment of a local coordinate system on the Gaussian integration point and the subsequent alteration of the stiffness integration. The results of numerical examples demonstrate that the high-precision iFEM is capable of effectively reducing the displacement difference resulting from inverse finite element method reconstruction. Furthermore, it performs well in practical engineering applications. [ABSTRACT FROM AUTHOR]

Gas extraction is crucial for coal mine safety, yet pipeline blockages by solid slag and water severely hinder efficiency and pose risks. Traditional detection methods are limited by rapid signal attenuation and noise interference. In this study, an acoustic detection technology is introduced for pipeline blockages, utilizing sensors at potential blockage points to collect sound wave data. Experiments with a scaled pipeline model reveal that slag blockages produce characteristic peaks in the 1200 Hz–2000 Hz range, while water blockages show peaks in the 1 kHz–2 kHz and 3.5 kHz–4.5 kHz bands. The longitudinal blockage intensity and extraction pressure significantly affect the sound pressure levels. A reliable fitting model predicts the blockage intensity based on acoustic signals, achieving high accuracy. This novel method enhances blockage identification, offering a non-invasive, cost-effective solution that improves coal mine safety and efficiency. [ABSTRACT FROM AUTHOR]

The characteristics of gas seepage in broken coal and rock composed of different particle sizes and grades were investigated in this study. On the basis of Darcy's law and non‐Darcy seepage theory, equations of gas permeability in the nonlinear seepage of broken coal and rock, as well as the porosity of broken coal and rock, under triaxial compression were determined. The stress loading path of gas seepage in broken coal and rock was developed. The characteristics of gas seepage in broken coal and rock composed of different particle sizes and grades were analyzed, and the results showed that the gas permeability after compression was proportional to the particle size of the broken coal and rock. Under triaxial compression, the gas permeability of the broken coal and rock composed of graded‐particle sizes was lower than that of the broken coal and rock composed of different single‐particle sizes. The gas permeability of the broken coal was lower than that of the broken rock mass, and the gas permeability and porosity of the broken coal and rock can be described by the exponential decay function. At a constant porosity, the gas permeability of the broken coal and rock was proportional to the size grading index under triaxial compression. The coefficient of viscosity and gravity of the flow are key factors influencing the flow permeability in broken coal and rock. This study provides a reference for on‐site practice such as the efficient extraction of gas in goafs. [ABSTRACT FROM AUTHOR]

This study conducted a cyclic loading–unloading (CLU) test on broken coal samples with three particle sizes (0–5 mm, 5–10 mm, and 10–15 mm) under four different stress path conditions. The evolution permeability characteristics of samples during repeated compaction were investigated. The dimensionless permeability and the porosity variation law were obtained under CLU conditions. The permeability loss difference (PID) index was defined, and the permeability damage was analyzed. The permeability evolution model under mining influence conditions was constructed. Results indicate that an increase in maximum loading stress (MLS) exacerbates the seepage network channel destruction of broken coal. As the MLS increases, there is a decrease in permeability recovery rate during the unloading stage and an increase in permeability loss rate during the loading stage. The first stress loading results in a rapid reduction in the porosity, while the subsequent CLU has a minor impact on porosity variation. Results of the PID analysis show positive correlation between the permeability attenuation degree and the MLS. Furthermore, both the permeability recovery rate and the permeability loss rate increase with increase in particle size, indicating that the effects of pressure relief and stress recovery have a greater influence on larger particles. Theoretical permeability values of model were verified with test results, and their high consistency proves the permeability evolution model's feasibility. The results will help provide theoretical guidance for gas extraction in goaf. [ABSTRACT FROM AUTHOR]

The stress-induced evolution of coal fractures significantly affects permeability and, consequently, gas extraction efficiency. This study introduces a novel coal fracture evolution model based on assumptions of fracture morphology and log-normal distribution of fracture aspect ratio. This model offers a theoretical framework for understanding the fracture closure process, ultimately depicting fracture evolution as a combined result of elastic compression and closure. It predicts the decay curve of fracture porosity under hydrostatic pressure loading. We conducted uniaxial compression experiments for determining the mechanical parameters of the model and in situ CT experiments with confining pressure ranging from 0 to 25 MPa for validating the model. The findings indicate the following: (1) Initially, the decline in fracture porosity with stress is predominantly due to elastic compression, followed by a rapid transition to closure. (2) Sensitivity analysis reveals that an increase in two physical quantities—the cube root of the product of the peak aspect ratio and the square of the mean aspect ratio (xc) and the bulk modulus of the coal matrix (Km)—results in a decrease in the rate of fracture porosity decay with stress. (3) Tectonic action has a dual effect of augmenting xc and diminishing Km. We define the magnification of xc and the divisor of Km under a common term—scaling factor. When the scaling factor of xc is less than that of Km, the tectonic action promotes the decay of porosity with stress. Conversely, when the scaling factor of xc is greater than that of Km, the effect is reversed. [ABSTRACT FROM AUTHOR]

Copyright of Science & Technology of Food Industry is the property of Science & Technology of Food Industry Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the study, a combined numerical simulation and on‐site monitoring method was used to analyze the asymmetric development characteristics of overlying rock fractures in a goaf under the condition of a goaf side entry formed by roof cutting and to explore the gas accumulation area in the goaf, achieving precise gas extraction from the goaf. The results demonstrates that a double‐balanced arch structure is formed under the condition of a goaf side entry formed by roof cutting, achieving safe retention of the roadway and showing the significance of the pressure relief effect of roof cutting. The collapse movement of the overlying rock on the roof‐cutting side is relatively advanced. The heights of the collapse zone on the roof‐cutting side and the uncut roof side are 28 and 24 m, respectively, and the development heights of the fracture zone are 37 and 42 m, respectively. The fault line on the roof‐cutting side gradually shifts toward the direction of the goaf, and the surface settlement and fracture development are relatively small. There is a clear asymmetric structure in terms of time effect, fault line, fracture zone height, and surface settlement compared to the uncut roof side. The gas is distributed throughout the entire goaf in the roof‐cutting and tunneling mode, and a high‐concentration gas accumulation area is formed near the open–off cut and working face on the high side of the fracture zone. Based on an actual situation, a method of drilling high and low positions in a fracture zone is proposed for extraction. Combined with on‐site monitoring, the goaf was no longer filled with gas during extraction, and the proportion of low‐concentration gas space considerably increased. [ABSTRACT FROM AUTHOR]

Copyright of Iraqi Journal of Chemical & Petroleum Engineering is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study is focused on the optimization and application of an analytical methodology for the determination of 15 selected pesticides in three substrates during the vinification process. QuEChERS extraction was used followed by GC-MS to develop a simple and rapid method for the determination of these compounds. The optimized methodology was validated, providing for all selected pesticides excellent linearity, recoveries ranging between 60.9% and 95.0% and LOQs lower than 50 ng g−1 f for all substrates. The developed methodology was tested on real samples of grapes, must and wine obtained from a winery in the Epirus region. The results indicated the existence of some of the selected pesticides at comparatively low levels in contrast to the valid MRLs. [ABSTRACT FROM AUTHOR]

Copyright of Coal Geology & Exploration is the property of Xian Research Institute of China Coal Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Coal Geology & Exploration is the property of Xian Research Institute of China Coal Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The alternating stress caused by periodic high-pressure injection and extraction in gas storage can potentially induce fault slippage, compromising the sealing integrity of faults within these storages sites. Understanding the mechanical behavior of faults under alternating stress is crucial for ensuring the long-term stability and safety of gas storage operations. To explore the impact of fault dip angle and fault gouge strength on fault slip characteristics, fault samples were prepared with uniaxial compressive strengths of 20.1, 30.2, 42.4, and 51.4 MPa at two distinct dip angles. Triaxial compression experiments were conducted under alternating stress conditions corresponding to operational pressures at a specific gas storage site in China. The results indicate that faults with dip angles of 30° and 45° tend to fail at their weakest points. The increasing strength of fault gouges shifts failure mechanisms from interfacial failure between gouges and the surrounding rock towards internal gouge failure, often accompanied by shear failure across sections, resulting in characteristic "X"-shaped conjugate shear failures. The decrease in the ratio of bedrock strength to fault gouge strength elucidates the observed phenomena of an initial reduction followed by increased fault deformation. Transition points for faults with 30° and 45° dips occur around the strength ratios of 1.7/1 and 1.2/1, respectively. Fault damage exhibits a negative correlation with fault gouge strength and a positive correlation with fault dip angle. Samples with a higher-strength fault gouge at a 30° dip angle generally incur less damage compared to those with a lower-strength fault gouge at a 45° dip angle. Moreover, higher maximum static friction coefficients denote greater fault resistance to slipping, with 30° faults consistently demonstrating superior resistance compared to 45° faults. Additionally, a higher-strength fault gouge consistently enhances slip resistance under identical dip angles. [ABSTRACT FROM AUTHOR]

Abstract In the study, a combined numerical simulation and on‐site monitoring method was used to analyze the asymmetric development characteristics of overlying rock fractures in a goaf under the condition of a goaf side entry formed by roof cutting and to explore the gas accumulation area in the goaf, achieving precise gas extraction from the goaf. The results demonstrates that a double‐balanced arch structure is formed under the condition of a goaf side entry formed by roof cutting, achieving safe retention of the roadway and showing the significance of the pressure relief effect of roof cutting. The collapse movement of the overlying rock on the roof‐cutting side is relatively advanced. The heights of the collapse zone on the roof‐cutting side and the uncut roof side are 28 and 24 m, respectively, and the development heights of the fracture zone are 37 and 42 m, respectively. The fault line on the roof‐cutting side gradually shifts toward the direction of the goaf, and the surface settlement and fracture development are relatively small. There is a clear asymmetric structure in terms of time effect, fault line, fracture zone height, and surface settlement compared to the uncut roof side. The gas is distributed throughout the entire goaf in the roof‐cutting and tunneling mode, and a high‐concentration gas accumulation area is formed near the open–off cut and working face on the high side of the fracture zone. Based on an actual situation, a method of drilling high and low positions in a fracture zone is proposed for extraction. Combined with on‐site monitoring, the goaf was no longer filled with gas during extraction, and the proportion of low‐concentration gas space considerably increased.

Abstract Gas extraction drilling is a necessary measure for managing gas hazards. For soft coal seams where gas extraction drilling holes are prone to collapse, it is believed that drill rod disturbance is the main cause of hole collapse. This study proposes a research approach to reduce wall stress by optimizing the drill rod structure. Through theoretical analysis, numerical simulation, and industrial tests, a stress model for the drill rod inside the hole was established, and a wall stress equation was derived. The effects of various parameters on wall stress were analyzed. The study suggests optimizing the drill rod structure to reduce the disturbance‐induced wall stress. SolidWorks was used for drilling stress simulation, and a four‐winged concave groove drill rod was developed. After strength verification, comparative industrial tests were conducted. The research results show that as the line density increases, the wall stress of the drilling hole increases. As the length of the suspended section increases, the wall stress initially decreases and then increases. With increasing drilling thrust, wall stress increases linearly, and the growth rate is greater with a larger diameter difference between the drill hole and the drill rod. Numerical simulation results indicate that the critical point maximum stress at the hole entrance, the critical point maximum stress at the hole bottom, and the average stress at the bottom section of the four‐winged concave groove drill rod with a concavity of 5 are significantly reduced compared to those of circular and grooved drill rods. Industrial test results show that using the four‐winged concave groove drill rod significantly reduces the extent of hole collapse. This study provides a reference for addressing the issue of hole collapse in gas extraction drilling for soft coal seams.

Abstract The controlled shock wave (CSW) fracturing is an effective method for enhancing permeability of coal seam to promote gas extraction. Based on Fick’s law, Darcy’s law, the ideal gas law and the Langmuir equation, a damage-seepage-deformation coupling mathematical model of CSW fracturing in coal seam combined with the maximum tensile stress and the Mohr-Coulomb criterion is established. This model is implemented into COMSOL Multiphysics to simulate the coal seam CSW fracturing and subsequent gas extraction. When the shock wave and isotropic in-situ stress are applied on the borehole wall, the coal damage zone is an annular shape, and the permeability in the damage zone increases sharply. The CSW can effectively increase the efficiency of gas extraction and reduce the gas pressure and gas content in coal seam. With the increase of CSW action times, the damage in coal mass reaches a threshold and tends to be stable after several shocks. The damage area and the gas extraction efficiency are positively correlated with the shock intensity. Under the anisotropic ground stress, the larger diversity of the stress in different directions is, the more obvious damage extension in the fractured coal along the maximum stress direction is. Ground stress can inhibit the extension of cracks in the CSW fractured coal seam. This inhibition effect becomes more obvious with the increase of in-situ stress. Parameters are substantiated of controlled shock wave impact on the coal seam, which ensures increased methane extraction from low-permeability reservoirs, are substantiated.

Abstract Coal (Rock) pillar retaining in the mining of protective layer would cause gas dynamic disaster in the protected layer. Based on the gas geological conditions of the two-layer coal seam in Jinhe Coal Mine of Yaojie Mining District, the stress evolution law of coal seam in the rock pillar affected area was studied by theoretical analysis and numerical simulation, and the crack development law of coal seam in different loading stages under conventional triaxial loading was studied by CT scanning technology. With the analysis of the stress evolution and crack development of coal in rock pillar affected area, the gas extraction effect under different stress states and the gas desorption law after pressure relief antireflection were studied on site. The results showed that the stress of coal in the rock pillar affected area is in the approximate elastic stage of the conventional triaxial stress-strain curve, and the cracks of coal are mainly closed at this stage. Meanwhile, the increase of stress leaded to the decrease of coal permeability and the poor gas extraction effect. CT scanning tests under conventional triaxial loading were carried out in the laboratory, and three-dimensional visual models of coal sample cracks were constructed at different loading stages. When loading to the linear elastic stage, the crack volume and surface area were reduced by 74% and 71% compared with the ones in initial state. At the same time, the expression between stress σ and crack density T was further established. After comprehensive control measures such as intensive drilling discharge, presplitting blasting and coal water injection were taken to the coal in rock pillar affected area, the crack density T could reach the crack development level of the conventional triaxial loading softening stage, realizing the crack development of the coal under low stress. The enclosed gas in front of the coal could desorption flow during the roadway driving. And the predict index value K 1 also decreased from 0.57 mL/(g·min 1/2) to 0.17 mL/(g·min 1/2) continuously. The safety of coal roadway in rock pillar affected area was realized, and the accuracy of numerical simulation and laboratory test results was verified, which had certain reference significance for coal roadway excavation under this similar conditions.

Hydraulic cavitation in coal seam can increase the permeability of coal seam and improve the efficiency of gas extraction. However, the analysis and calculation method of throttling control mechanism of hydraulic cavitation bit is still not perfect. In this paper, firstly, the composition of hydraulic cavitation device, the detailed process of hydraulic cavitation, the structure and principle of hydraulic cavitation bit and the mechanism of throttling tube are introduced. Then, the flow inside the throttling tube is simplified into one-dimensional fluid for analysis. According to the continuity equation, momentum equation and Bernoulli equation, the mathematical expression of the pressure distribution inside the throttling tube is deduced, and the pressure distribution curve inside the throttling tube is drawn. Secondly, the simulation model of the throttling tube is established according to the turbulence model, and the pressure distribution and velocity distribution inside the throttling tube are analyzed. Finally, the opening and closing experiment of the hydraulic cavitation bit is carried out, and the relationship between the opening and closing flow and pressure of the hydraulic cavitation bit, the reduction diameter of different throttling tubes and the pressure drop value is studied. This study provides the drilling tool support for gas extraction and permeability enhancement in low-permeability coal seam, and provides the theoretical support for the design of throttling pipe of hydraulic cavitation drill.

In the process of CO2-enhanced coalbed methane recovery, the behaviours of coal seam fractures significantly affect sequestration and extraction. To address the unclear impact of fracture roughness evolution on engineering efficiency under multi-physical field coupling effects, we developed an innovative interdisciplinary mathematical model. This model introduces a parameter to quantitatively describe coal seam fracture roughness and couples it with the gas flow control equations under multi-field effects in the coal seam. We investigated the thermo-hydro-mechanical (THM) coupling effects and fracture network characteristics in the coal seam gas extraction process. Results show that the mathematical model aligns well with field data and effectively characterizes coal seam fracture roughness. Fracture roughness significantly influences the residual gas pressure in the coal seam and the injection pressure of CO2. When the roughness parameter decreases from 0.24 to 0.18, the maximum methane content decreases by 32.5% and the maximum CO2 pressure increases by 26.7%, the maximum gas adsorption capacity of coal seam decreased by 31.7%, and the maximum CO2 adsorption capacity increased by 12.1%.

The drilling effect of complex and weak coal seams is of great significance for gas extraction in mines. A ZDY6000LR high-speed tracked drilling rig with high rotational speed, high power, and high torque performance was designed to address the problems of difficult slag removal, high accident rate, and hole formation during the drilling construction of complex and weak coal seams in Wangpo Coal Mine. The maximum torque was 6 000 N·m and the maximum speed was 400 r/min. The layout, power head, angle adjustment mechanism, feed body, and hydraulic system of the drilling rig were optimized to ensure that the problems such as sticking and collapsing during the drilling process can be effectively solved during the construction process. The ϕ95/ ϕ60.3 mm wide blade insert sealed auger rod with high strength and not easy to break teeth is developed and designed, and the ϕ113 mm, ϕ120 mm, ϕ133 mm triangular ladder PDC bits with high strength and low risk of broken teeth are also designed. The on-site industrial test at the 3206 working face of Wangpo Coal Mine has shown that this set of drilling equipment and drill assembly effectively solved the problems existing in the construction process such as slag discharge difficulty and top drilling of the jet hole, and improved the hole formation rate of the drilling, and the hole formation rate of the drilling above 100 meters was more than 70%, which provided an important support for the gas extraction of the coal seam of the mine.

Coal reservoirs are often connected to hydrogeological systems through faults, allowing groundwater with mineralization to intrude into coal seams. In order to improve gas extraction, it is necessary to explore the effect of coal with different moisture content and salinity conditions on CH4 adsorption. By means of various experimental tests, such as XPS, FTIR, we constructed macromolecular structure models of Dongqu 8# coal with different moisture content and salinity conditions, conducted isothermal adsorption simulation experiments, and analyzed in detail the effects of coal models with different moisture content and salinity conditions on the adsorption capacity of CH4. The results showed that the adsorption capacity of CH4 decreased with the increase of moisture content and salinity in coal; the effect of moisture content on CH4 adsorption was greater than that of salinity on CH4 adsorption; the ability of sodium salt to affect the adsorption of CH4 by coal was ranked from largest to smallest as follows: Na2CO3 > NaHCO3> NaCl; electrostatic potential distribution: | Na2CO3 electrostatic potential| > | NaHCO3 of electrostatic potential| > | NaCl of the electrostatic potential|, it can be seen that the electrostatic force affects the strength of adsorption, the greater the value of the electrostatic potential of the ions in the salt, the stronger ability the coal to adsorb CH4.

Abstract The gases released by underground coal mining pose a threat to mine safety, lead to resource wastage, and contribute to environmental pollution. Employing long horizontal boreholes (LHB) for gas extraction proves to be an effective solution. However, accurately determining the LHB's position within the overlying rock strata is challenging due to complex mining and geological conditions. This study introduces a novel “zone‐position” method for identifying the optimal LHB placement, utilizing both physical simulation tests and theoretical analysis. The approach comprises two steps. Initially, it identifies the appropriate LHB layout zone within the overlying strata. It delineates four subzones within the fractured zone, among which the stable fractured subzone (SFSZ) is identified as the most favorable for LHB placement. The boundaries of the SFSZ are also defined. Subsequently, the method focuses on pinpointing the LHB's precise location within the SFSZ, proposing a criterion that considers gas accumulation, strata permeability, and LHB stability. Application of this method in engineering projects demonstrates that the gas extracted by LHBs accounts for about 60% of the total gas emission. Furthermore, the volume of gas extracted at the optimal LHB location reaches up to 5.52 m3 min−1, triple that of other locations.

Abstract To investigate the effects of different crustal stresses on the stability of gas extraction boreholes, several equations were deduced. Additionally, the coupled flow‐solid model of gas extraction was constructed, given the elasticity−plasticity deformation of the coal body. Using the numerical simulation and analysis software of Comsol, a study was conducted on the deformation and damage of gas extraction boreholes under different crustal stresses. The results are as follows: with vertical stress increasing, the concentration area of shear stress, deformation amount, and the area of the plastic zone around the hole increase. Varied lateral pressure coefficients led to differing distribution positions of shear stress concentration areas and plastic zones around the hole. An increase in lateral pressure coefficient shifted the distribution positions of shear stress maximum. In addition, plastic zone, and permeability ratio maximum change from the left and right sides of the borehole to the upper and lower sides, and the larger the lateral pressure coefficient is, the worse the stability of the upper and lower sides of the borehole is. Higher lateral pressure coefficients inhibited extraction, with the effect becoming more pronounced over time. Elevated vertical stress and lateral pressure coefficients hindered negative pressure propagation in the borehole.

The evolution of fractures in mining overburden plays a pivotal role in interlayer gas migration. Therefore, a comprehensive study of crack development and distribution improve the efficiency of gas extraction. This study the west 2107 fully mechanized mining face in Weijia Mine of Gansu Province as the engineering background, Specifically, this study established numerical models of different mining heights by using the UDEC simulation software, and analyzed the relationship between the evolution of near-field fractures in the overburden of the working face and different mining based on fractal geometry theory. The optimal working face height for gas extraction was determined and validated through theoretical empirical formulas, field observations of overburden fractures, and gas extraction results. The results show that the total number of mining fractures increases with the increase of mining height, but the amplitude of increase is different at different stages, and the overburden fractures continue to develop in an "umbrella" shape around the overburden. The near-field fractures of the overburden rock at different mining heights have undergone three stages: generation, expansion and penetration, and compaction stability. Increasing mining height, smaller compaction zones. When the mining height is 4 m, the development density and range of roof fractures at 10 m and 40 m are significantly higher than those in other areas, which is consistent with the optimal position of the collaborative extraction roadway with high and low roadways.

In this study, a new method is proposed to quantitatively determine the extraction of boreholes under the effect of time. The main purpose of this method is to divide the gas drilling holes in the monitoring time into two stages: the early stage of extraction and the middle stage of extraction. The early stage of extraction uses the gas pressure difference to detect the gas tightness of the drilling holes and determine the type of gas leakage of the drilling holes. Moreover, the unqualified drilling holes are repaired immediately to ensure that all the drilling holes in the middle stage of the monitoring are the qualified holes at the early stage of the inspection. In the middle of extraction, the average attenuation rate of the fitting attenuation curve of pure gas extraction in the extraction borehole is calculated by monitoring, the growth rate of the linear fitting of the pure air leakage is calculated, and their ratios are used as the basis for judging the repair value of the gas leak borehole and the gas leak borehole. This quantitative evaluation method is used to monitor the extraction effect of four test holes in a field test conducted at Ping Coal Mine 10. The results indicate that, after adopting in situ downhole repair technology in the early stage of extraction, the average air leakage of Borehole No. 4, which failed due to air leakage in the borehole, decreased from 9.33 to 1.26 L/min (a reduction of 86.5%). Similarly, that of Borehole No. 3, which failed due to penetration of fissures in the surrounding rock, had an air leakage drop from 8.35 to 1.34 L/min (a reduction of 84.0%). These improvements demonstrate the remarkable effectiveness of the method. The quantitative evaluation method established in this study is not only simple to operate but also stable and reliable. Thus, it is feasible to be applied in the field, which provides important technical support for the improvement in gas extraction effect during coal mine safety production. [ABSTRACT FROM AUTHOR]

As challenges in gas extraction from coal mines increase, precise measurement of permeability becomes crucial. This study proposes a novel pulse transient method based on a fractional derivative model derived on physical fractal space, incorporating operator algebra and the mechanics–electricity analogy to derive a new control equation that more accurately delineates the permeability evolution in coal. To validate the approach, permeability experiments were conducted on coal samples under mining stress conditions. The results showed that the adoption of a physically meaningful fractional-order relaxation equation provides a more accurate description of non-Darcy flow behaviour in rocks than traditional integer-order control equations. Additionally, the method proved effective across different rock types, verifying its broad applicability. By establishing a new theoretical foundation, this approach illustrates how the microscale fractal structure of rocks is fundamentally linked to their macroscale fractional responses, thereby enhancing the understanding of fractional modelling methods in rock mechanics and related domains. [ABSTRACT FROM AUTHOR]

As intelligent mining operations evolve, stringent standards for gas management and extraction are imperative. To mitigate the risks associated with coal and gas outburst and to prevent gas concentration from exceeding safe limits, a comprehensive three-dimensional gas extraction system is introduced. This method, exemplified by the 1075 intelligent working face at the Yangliu coal mine, integrates temporal and spatial considerations for comprehensive extraction. Utilizing COMSOL and UDEC simulations, the extraction parameters for both pre-extraction and mid-mining extraction have been meticulously optimized. The optimal strategy involves boreholes with a diameter of 113 mm, spaced 3 m apart, and an initial negative pressure of 31 kPa, which is subsequently reduced to 13 kPa as gas levels decrease. The positioning of directional high-level boreholes is determined by the fracture zone distribution in the goaf's overlying strata, placed 19–25 m above the roof and 0–65 m from the return airway. Directional interception boreholes are optimally located 54–73 m above the roof. Surface wells are strategically positioned 15 m above the roof, with a horizontal distance of 30–65 m from the return airway. After extraction of the system, the maximum gas concentrations recorded in the return airway and the upper corner are 0.26% and 0.27%, respectively. The average daily production reached 5258 t, nearly doubling the overall efficiency. This gas extraction technique not only enhances the efficiency of intelligent mining operations but also serves as a valuable reference for future research in the field. [ABSTRACT FROM AUTHOR]

Copyright of China Mining Magazine is the property of China Mining Magazine Co., Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Natural gas hydrate is a kind of low-carbon and clean new energy, so research on its efficient extraction in terms of theory and technology is particularly important. Combined thermal injection and depressurization is an effective method for extracting natural gas hydrate. In this study, the classical local heat equilibrium model was modified, and a pore-scale fully coupled unsteady heat transfer model for hydrate reservoirs was set up by considering multiple forms of heat flow accompanying hydrate's decomposition and gas–liquid flow. Based on this model and the basic geological information of the X2 hydrate reservoir in the western Pacific Ocean, a numerical model of gas hydrate extraction using combined heat injection and depressurization was constructed to simulate the production performance of the hydrate reservoir. The results were fully compared with the results obtained by the depressurization method alone. The results indicated the hydrate extraction via a combined heat injection and depressurization would have a cumulative gas production of 31.609 million m3 and a cumulative water production of 1.5219 million m3, which are 72.57% higher and 31.75% lower than those obtained by depressurization alone, respectively. These study results can provide theoretical support for the industrial extraction of gas hydrate in seas. [ABSTRACT FROM AUTHOR]

Hydraulic measures such as hydraulic slotting and hydraulic fracturing are commonly used in coal seam pressure relief and permeability enhancement. Two-phase flow patterns of CH4–water in pore-sized coal seams after hydraulic measures are critical to improve gas extraction efficiency. The phase field module in COMSOL Multiphysics™ 5.4 and the classical ordered porous media model were used in this paper. The characteristics of CH4–water two-phase immiscible displacement in coal seams under different capillary numbers (Ca) and viscosity ratios (M) were simulated and quantitatively analyzed. By changing the contact angle of the porous media, the flow patterns of CH4–water two-phase in coal with different wettability were simulated. Results show that wettability significantly affects the displacement efficiency of CH4. Additionally, by constructing a dual-permeability model to simulate the varying local permeability of the coal, the flow patterns of different Ca and M in dual-permeability media were further investigated. It is found that CH4 preferentially invades high-permeability regions, and the displacement efficiency in low-permeability regions increases with higher Ca and M, providing a reference for gas extraction from coal seams after hydraulic measures. [ABSTRACT FROM AUTHOR]

Poor sealing of gas extraction boreholes is one key to restrict gas extraction efficiency. In this paper, a novel borehole sealed quality detection device for the gas extraction of a coal mine is developed based on the theory of air leakage. By comparing the amount of gas extracted at different test points, it is possible to determine whether there is air leakage around the borehole, and the specific leakage position and leakage amount. Moreover, this device has the advantages of simple operation and a short test period. Based on the above analysis, a corresponding air leakage disposal method was proposed to handle the leaky boreholes. Field tests showed that the air–gas mixture flow in the test borehole was reduced by a factor of approximately 1.55 and the concentration of pure seam gas was increased approximately six times after the disposal of the air leaks. The combination of the leakage disposal method and the leakage detection device can accurately seal the borehole at the position of the leak, thus effectively ensuring the effectiveness of gas extraction from the borehole. The findings have important implications for improving the efficiency of gas extraction in coal mining operations. [ABSTRACT FROM AUTHOR]

Natural gas is widely used in many homes for cooking, but a lack of gas leak detection has led to large fires and accidents. This article presents the design and implementation of a natural gas detection and extraction system for domestic kitchens in Lima, Peru. The ESP32 microcontroller allowed remote circuit control, resulting in a more convenient setup than the Arduino UNO microcontroller. After calibration of the sensors and their corresponding programming, three actions were established in response to different gas levels: alarm activation, space ventilation and gas extraction, and thermal shutdown. Strategic sensor placement and improved physical presentation of the system were performed to ensure accurate readings and effective deployment. The results demonstrate the proper functioning of the circuit and its ability to prevent accidents related to gas leaks. The designed system offers the advantage of remote monitoring, providing access to the user from any location. In conclusion, this project offers a comprehensive solution to prevent accidents caused by gas leaks in home kitchens. With satisfactory results in terms of operation and rapid response, the project demonstrates its effectiveness in accident prevention. This design offers a practical and accessible solution, improving security and bringing peace of mind to homes. [ABSTRACT FROM AUTHOR]

Hazard and risk assessment of complex petroleum-derived substances has been in a state of continuous improvement since the 1970s, with the development of approaches that continue to be applied and refined. Alternative feeds are defined here as those coming into a refinery or chemical plant that are not hydrocarbons from oil and gas extraction such as biologically derived oils, pyrolysis oil from biomass or other, and recycled materials. These feeds are increasingly being used for production of liquid hydrocarbon streams, and hence, there is a need to assess these alternatives, subsequent manufacturing and refining processes and end products for potential risk to humans and the environment. Here we propose a tiered, problem formulation-driven framework for assessing the safety of hydrocarbon streams and products derived from alternative feedstocks in use. The scope of this work is only focused on petrochemical safety assessment, though the principles may be applicable to other chemistries. The framework integrates combinations of analytical chemistry, in silico and in vitro tools, and targeted testing together with conservative assumptions/approaches to leverage existing health, environmental, and exposure data, where applicable. The framework enables the identification of scenarios where de novo hazard and/or exposure assessments may be needed and incorporates tiered approaches to do so. It can be applied to enable decisions efficiently and transparently and can encompass a wide range of compositional space in both feedstocks and finished products, with the objective of ensuring safety in manufacturing and use. [ABSTRACT FROM AUTHOR]

The large quarry face with a strike length of 3 300 m in Sijiazhuang Mine features high gas reserve,large gas outflow and its upper corner is easy to exceed the limit. This study adopts the gas management technology of extracting the gas from the coal seam by drilling large-diameter downhole holes. We established a numerical model of fluid-solid coupling by considering the superposition effect of drill holes to analyze the evolution of gas pressure,effective extraction radius,and the effect of gas extraction when the diameter of drill holes is 113 mm and 400 mm respectively. The results show that ©after implementing pre-extraction technology in the large diameter drill hole,the effective extraction radius of the drill hole increased by 21. 12% ;©When introducing the coefficient k =pm / pc as a judgment index of the superposition effect,taking the effective extraction radius of a single 113 mm diameter drill hole as a reference,the effective radius of a 113 mm diameter drill hole is improved by 3. 7 times compared with that of a single hole when using a common diameter drill hole for multi-hole extraction; ©The concentration of the gas extracted from the drill hole increased by 2 times,and the pure amount of extraction increased by 5 times,which provides technical and theoretical references for the gas management and safe production of the working face of large mining fields. [ABSTRACT FROM AUTHOR]

Under the background of intelligent construction of coal mines, gas extraction design is still based on manual design, which is complex, time–consuming, and error–prone, and its automation degree needs to be improved. In order to solve this problem, taking the 1302 working face of a mine in Shanxi Province as the research object, this paper carried out relevant research. Firstly, the influencing factors of gas extraction were determined, and the influence rules of different parameters on the extraction effect were studied by numerical simulation. Secondly, an intelligent optimization method of gas extraction drilling parameters based on deep mining called the PSO–LSTM model, is proposed. This model uses the PSO algorithm to optimize the parameters of the LSTM model, so as to improve the accuracy of the LSTM model results. Finally, a quantitative expression algorithm of 3D spatial information of gas extraction drilling holes based on Python is proposed, which can automatically generate 3D spatial models of bedding or through gas extraction drilling holes using optimized drilling parameters and known 3D information of coal seams. This study shows that the results obtained using the PSO–LSTM model are the same as the drilling parameters obtained using numerical simulation, which verifies the accuracy of the PSO–LSTM model. According to the optimized drilling parameters, a 3D model of gas extraction drilling is quickly generated, which greatly reduces the tedious work of drawing construction drawings for coal mine enterprises and improves the intelligence level of coal gas extraction drilling. [ABSTRACT FROM AUTHOR]

Coal seam cavitation is one of the most effective techniques for gas disaster control in low-permeability coal. Due to the difference in cavitation method and process, the damage degree and fracture development range of the coal body around the cavern are greatly different, and the effect of increasing the permeability of the coal body is further changed. In order to further understand the permeability enhancement mechanism of cavitation technology on low-permeability coal and effectively guide engineering applications, this paper conducted experimental research on the unloading damage and permeability evolution characteristics of coal under different cavitation paths using a coal-rock "adsorption-percolation-mechanics" coupling test system. Through the analysis of coal strength and deformation characteristics, coal damage characteristics, and the evolution law of coal permeability combined with the macroscopic damage characteristics of coal, the strength degradation mechanism of unloaded coal and the mechanism of increased permeability and flow were revealed. The results show that unloading can significantly reduce the strength of coal, and the greater the unloading rate, the more obvious the reduction. The essence of this is that unloading reduces the cohesion and internal friction angle of coal—damage and breakage are the most effective ways to improve the permeability of the coal body. Unloading damaged coal bodies not only significantly improves the permeability of the coal body but also improves the diffusion ability of gas, and finally, shows a remarkable strengthening effect of gas extraction. [ABSTRACT FROM AUTHOR]

With the increasing depth of coal mining, the ground stress of coal seams rises, the gas content rises, and the permeability decreases, which is unfavorable to gas extraction and increases the possibility of gas accidents in coal mines. Blasting technology is often used to improve the permeability of coal seams and increase the effect of gas extraction, but it is difficult to control the blasting effect of ordinary flux coils, and the direction of the fissure and the degree of development of randomness, so it is important to study the effect of different flux coil structures on the blasting of coal seams to increase the permeability of the coal seam, in this paper, first of all, through the numerical simulation to analyze the effect of the blasting of the ordinary structure flux coils and the fissure change in the polygonal structure flux coils, and then make the experimental module. Then, we make the test module, build the test platform, and analyze the effect of blasting penetration of different drug coil structures by comparing the strain after blasting and the change in resistivity before and after blasting of two kinds of drug coil structures, and the results show that the polymerized drug coil can play the role of directional fracturing, and compared with the ordinary structure of the drug coil, the polymerized drug shows a better effect of fracturing and penetration increase. [ABSTRACT FROM AUTHOR]

To explore the impact of different factors on the effectiveness of borehole gas extraction, in situ stress tests were conducted in a test mining area. A theoretical model of gas migration within the coal matrix–fracture system was established. Based on field data, a numerical model was constructed to study the variation patterns of the effective extraction radius under different extraction conditions. Using the response surface methodology, the interactions of different factors and their impact on the effective extraction radius were analyzed, resulting in a response surface model for each factor and the effective extraction radius. The results indicate that the initial permeability of the coal seam has the greatest impact on the extraction radius, with a maximum range of 2.027 m. The influence of extraction time, extraction negative pressure, and borehole diameter decreases sequentially. The borehole diameter has the least impact, with a range of 0.608 m. The response surface model has good significance, with a coefficient of determination (R2) of 0.9957, and it can explain over 99.57% of the response values. The response surface between the initial permeability of the coal seam and extraction time shows the greatest degree of distortion, indicating a significant interaction effect on the extraction radius. In contrast, the response surface between extraction time and extraction negative pressure shows the least degree of distortion, indicating that their interaction effect is the least significant. These findings can provide a theoretical reference for improving borehole design and enhancing gas extraction efficiency. [ABSTRACT FROM AUTHOR]

AbstractGamma irradiation is one of the preservation techniques used to increase the shelf life of foods. The current study was aimed to determine the volatile flavor contents of melon (Cucumis melo L.) seeds and the impact of gamma radiation upon these compounds. The seeds were irradiated with gamma rays at 1, 5, 10, and 20 kGy doses. The volatile compounds were extracted by simultaneous distillation extraction (SDE), using n-pentane/diethyl ether (1:1, v/v) and determined by gas chromatography-mass spectrometry (GC-MS). A total of 70 volatile flavor compounds were identified in the control, with 2,3-butanediole (18.01%) and 1-hexanol (6.06%) as the major compounds. The number and percentage of the volatile compounds varied with the gamma irradiation doses. Twenty-eight volatile compounds were present in the non-irradiated and irradiated samples at different concentrations. Up to the recommended gamma irradiation dose of 10 kGy, the number of volatile flavor compounds generally increased. There were changes in both the number and percentages of the identified volatile flavor compounds following gamma irradiation of the Cucumis melo L seeds. [ABSTRACT FROM AUTHOR]

The problem of hydrate plug, low efficiency of hydrate dissociation and short production time in hydrate exploitation processes have significantly hindered the commercial viability of gas hydrate extraction. This study investigated the inhibitory effects of ethylene glycol (EG), EG + polyvinyl pyrrolidone (PVP), and EG + PVP + sodium chloride (NaCl) on methane hydrate formation through experiment. The hydrate inhibitory performance is evaluated by using differential of pressure curve, the amount of hydrate, and pressure drop values, and the effects of different temperatures, pressures, inhibitors, and injection time on hydrate dissociation are further studied. The experiment results indicate that the rank of inhibitors combination in terms of effectiveness is 5%EG + 0.5 wt%PVP + 3 wt%Nacl > 10%EG + 1 wt%PVP > 30% EG. At low-temperature conditions, 30% EG exhibits good inhibition of hydrate synthesis but poor dissociation efficiency. As temperature increases, the hydrates dissociation rate with 30% EG also increases. For the combination inhibitor system of EG, PVP, and NaCl, PVP will reduce the dissociation efficiency of hydrates, while EG and Nacl will improve the hydrate dissociation performance. For low production pressure, it is found that 10% EG + 10% NaCl have a good promotion effect on hydrate dissociation, whereas under high production pressure, 20% EG + 10% NaCl is more effective. Furthermore, injecting the inhibitors earlier enhances the dissociation of hydrates more effectively. [ABSTRACT FROM AUTHOR]

During the shale gas extraction process, affected by the internal pressure of the geological layer and other factors, the internal pressure will gradually decrease with time, and the production will also decrease, and it is necessary to rely on artificial pressurization and other ways to keep the production stable. Accordingly, we analyzed the high-frequency data of shale gas production obtained from a block in the southwest shale gas field, and proposed a data-driven prediction model combining Principal Component Analysis (PCA), Particle Swarm Optimization (PSO) and Long Short-Term Memory (LSTM), which can determine whether artificial pressurization is needed from the predicted results. The model adopts multi-variate input and uni-variate output, firstly, the PCA algorithm for processing the characteristic parameters (casing pressure, oil pressure, pre-valve temperature) and labeling parameters (instantaneous production), secondly, the PSO algorithm is used to iteratively search for the optimal hyper-parameters of the LSTM to find the most suitable hyper-parameter configuration, and finally, established a data-driven shale gas production prediction model. The combined model is analyzed through an example study, and the accuracy is higher in shale gas production prediction. [ABSTRACT FROM AUTHOR]

This study proposed a novel development mode combining boundary sealing and hot water injection to address the challenges of gas leakage, limited reservoir sensible heat, boundary water intrusion, and low productivity faced by challenging hydrate extraction, and the stimulation effect was numerically investigated with Shenhu hydrates as the geological background. The results showed that lower boundary permeability facilitated pressure propagation and achieved volumetric dissociation of hydrates, whereas insufficient formation energy resulted in substantial gas retention. Hot water injection was effective for stimulation, but open boundaries could not maintain the high injection pressure, leading to massive hot water losses and gas escapes. However, their combination achieved a synergistic stimulation like "1 + 1 > 2" because a piston water drive similar to secondary recovery in oil and gas development was formed. Relative to three-spot well patterns, the five-spot shortened the extraction cycle by 680 days and enhanced the gas-to-water ratio by 17%. Increasing injection pressure enhanced water yield more significantly while the improvement of gas yield was more significant by increasing hot water temperature. Overall, high-pressure and high-temperature injection was suggested for gas enhancement and water control. These findings provide important guidance for advancing the commercial development of challenging hydrates. [ABSTRACT FROM AUTHOR]

The effectiveness of oil field development systems is largely determined by all possible methods of developing industrial oil reserves and the nature of production. The growth of production rates, high demand for petroleum products, require the complete extraction of oil from the subsoil. The main purpose of the study is to analyze the state of oil reserves production at the Severnaya Truva field by identifying problems that arise during the extraction of oil reserves in productive formations, increasing the intensity of oil production, analyzing the results of theoretical and experimental studies. In the exploration and exploration of oil and gas reserves, the productivity of the layer is important, since the physical environment of the layer changes with each molecule obtained during the extraction process, the longer the layer works, the more accurate the forecast of the remaining reserves. In the course of the study, the features of the geological structure of oil fields are studied, the influence on hydrodynamic processes in them is studied, work is being carried out to substantiate geological and professional criteria that determine effective development. The article examines the method of improving the methods of evaluating operational parameters and substantiating the design features of completion during the opening of capital-built deposits. It is envisaged to increase the production of oil reserves of capital-built fields by substantiating the technological parameters of well operation. [ABSTRACT FROM AUTHOR]