Geofluids最新文献

The purpose of this paper is to analyze the diffusion mechanism of polymer slurry in rough fractures under slurry–rock coupling, which has important practical significance for polymer grouting repair of rock fractures. The rock mass fracture with random roughness is constructed in the spatial frequency domain, and the random rough fracture slurry diffusion model is established; then, a model experiment is established to verify the accuracy of the numerical method. Finally, the fluid–solid coupling diffusion mechanism in the grouting process is analyzed. The results show that (1) the maximum flow rate of slurry increases with the increase of overall roughness. The coarser the fracture, the more irregular the velocity distribution along the fracture opening direction. (2) The stress in rough fractures gradually decreases with the direction of slurry diffusion. The rougher the fracture, the greater the stress fluctuation, the more phenomena of stress concentration appear at the tip. (3) The stress field is greatly influenced by the shape of fractures, in depressed areas, where stress mutations can easily lead to plastic damage and secondary fractures.

As the key engineering structure of continuous coal mining, the surrounding rock disaster mechanism of gob-side entry has always been a research hotspot. In purpose of researching the disaster mechanism of adjacent rock, this paper takes the background of the −240 working face of Dongbaowei 36^# coal seam as the backdrop, adopts the theoretical analysis, and calculates the dimension of the coal column, and the numerical simulation method analyzes the effect of the coal column on the deformation and damage characteristics of the adjacent rock and the stress environment, so as to put forward the control countermeasures of the adjacent rock and carry out the engineering validation. The results show that (1) based on the results of laboratory tests and field measurements, it is found that the destruction of the “roof–coal column” system is the main reason for the disaster of the adjacent rock. (2) Considering the influence of coal seam inclination, the preliminary determination of the dimension of the coal column ranges from 4.38 to 9.4 m; with this width increase, the deformation of the coal column is smaller, and the stress environment of the adjacent rock can be optimized. Considering the deformation characteristics of the adjacent rock, stress environment, and economic efficiency, it is more reasonable to determine the dimension of the coal column of 5 m. (3) The control countermeasures of coal pillar composite reinforcement technology and changing roof bolt cable parameters are put forward, and it is more reasonable to determine the bolt preload of the roof plate to be 75 kN and the pretightening force of the anchor cable to be 200 kN, and it is better for the roof plate anchor, anchor cable, and cooperative support effect; the on-site test found the maximum amount of the roof of the roadway to be 198 mm and the maximum amount of the two gangs to be 127 mm, which can meet the needs of the normal production. This study is aimed at providing theoretical and technical support for controlling the disaster of trapezoidal adjacent rock in inclined coal beds, as well as providing a reference for solving similar engineering problems.

Accurate and rapid regional production prediction in oil and gas fields is crucial for production management, workload allocation, and investment planning. Currently, oil companies primarily rely on the production composition method for regional oil production planning. However, this method suffers from poor timeliness and consumes substantial human and material resources. Unlike oil field production prediction, regional production planning is influenced by a greater number of macro factors, such as regional exploration resources, development strategies, and market conditions. Therefore, we have established a multidisciplinary sample set that comprehensively considers exploration indicators, development indicators, production indicators, and economic indicators. Additionally, we innovatively propose an SM-PSO-RF-LSTM production prediction model. This model optimizes hyperparameters based on an innovative SM-PSO hybrid algorithm and initializes feature indicators based on importance weights derived from random forests. We designed three sets of comparative studies: Study 1 demonstrates that, in terms of regional production prediction, the new method outperforms previous approaches in prediction performance; Study 2 proves that hyperparameter optimization using the SM-PSO algorithm can significantly enhance the prediction accuracy of the LSTM model; and Study 3 establishes that the regional production prediction method based on planning strategies is more consistent with actual planning results.

The Asal Rift is a continental rift segment in which the hydrothermal reactions of hot volcanic rocks and seawater-derived groundwater are comparable to the submarine hydrothermal processes. Formation of recent evaporites in the hypersaline Lake Asal and Lake Abhé is superimposed on this seafloor-type hydrothermal activity. From a geological and planetary science perspective, these continental rift lakes are valuable natural calibration fields for constraining the water–rock interaction and elemental cycles. In this study, we report on the chemical composition and stable isotopic fractionation of Mg, Sr, and Li in the hydrothermal fluids and brines of these two hypersaline lakes. The hydrothermal fluids of both Lake Asal and Lake Abhé were characterized by lower Mg isotopic ratios than seawater. This is explained by the removal of ²⁶Mg from the fluids during the hydrothermal fluid–basalt interaction. In contrast, the brine from Lake Asal is indistinguishable from seawater, and no apparent effect of evaporite minerals on δ²⁶Mg was observed. The ⁸⁷Sr/⁸⁶Sr and δ⁸⁸Sr values of the hydrothermal fluid vary within the same range as the basalt, indicating that the effect of Sr leaching from the rock is significant. In contrast, the variation in δ⁸⁸Sr is mainly caused by the precipitation of carbonates from the lake brine. The correlation between δ⁷Li and ⁸⁷Sr/⁸⁶Sr is clear regardless of the sample type (hydrothermal fluid, brine, or river water) and is thought to reflect the mixing of solutes. The δ⁷Li values of the hydrothermal end-members can be used as an indicator of the reservoir temperature of fluids.

The hydraulic characteristics of a single rough fracture are critical in rock seepage studies, with roughness being the dominant factor influencing fracture hydraulic behavior. In this study, four sets of single rough fractures with fractal dimensions ranging from 1.2 to 1.8 were generated using the Weierstrass–Mandelbrot function, and the evolution of the correction coefficient for rough fracture laminar flow rate based on the classical cubic law with fractal dimension was numerically investigated. The results demonstrate that fractal dimension significantly influences hydraulic aperture and hydraulic gradient along tortuous seepage paths, thereby altering the overall flow rate. For rough fractures with apertures below 2 mm under laminar flow, the maximum variations in the correction coefficient caused by different apertures and pressure differences at identical fractal dimensions were merely 1.07% and 2.09%, respectively. While the correction coefficients of seepage flow rate show minimal variation, maintaining values between 0.67 and 0.72 across the fractal dimension range of 1.2–1.4, it exhibits a rapid decline as the fractal dimension increases from 1.4 to 1.8, with values at 1.8 decreasing by 47.8% and 33.7% compared to those at 1.4 and 1.6, respectively. Finally, a fitting function was developed to characterize the relationship between the correction coefficient and the fractal dimension for single rough fractures. The research findings can serve as a reference for understanding and quantitatively characterizing the seepage properties of rough single fractures.

China boasts abundant reserves of close-distance coal seams, where mining operations face complex stress environments and roadway stability. The work took the simultaneous mining faces of ultraclose coal seams in the Huayuan Coal Industry of Lingshi, Shanxi Province, China, as the research subject. Theoretical analysis and numerical simulation were used to investigate the stress distribution patterns under simultaneous mining in ultraclose coal seams and the rational coal pillar width for the lower working face. First, based on the related mechanical model, a theoretical solution for the coal pillar width was derived under limit equilibrium. Furthermore, a discrete element numerical model was established to simulate the stress evolution and surrounding rock failure characteristics under the disturbance of the double-side goaf in the upper seam and the single-side goaf in the lower seam. Multisource disturbances led to stress peak superposition, easily forming a stress concentration zone at the center of the lower pillar. This posed a severe threat to the stability of the surrounding rocks in the lower roadway. An 8-m pillar width provided the optimal balance between resource recovery and roadway stability, based on the stress, displacement, and plastic zone distribution observed across different pillar widths. Finally, in terms of stress redistribution, the roadway support parameters were optimized and applied on-site, with a favorable support effect achieved. The research findings provide theoretical foundations and engineering guidance for the layout and support design of lower roadways in ultraclose coal seam groups.

The microseepage activity in Chaoshan Depression is obvious, and the relationship between microseepage and oil–gas reservoirs is a matter of great concern. Submarine hydrocarbon gas seepage includes macroseepage and microseepage; a large number of macroseepage studies have been investigated in the South China Sea, but relatively little is known about microseepage, and very few studies of microseepage in oil–gas exploration have been carried out. Chaoshan Depression is a Mesozoic and Cenozoic superimposed depression in the northern South China Sea; it has good potential for oil–gas exploration, but oil and gas have not been discovered through drilling. Effective identification and prediction of favorable exploration areas and reservoirs are the keys to successful exploration. In this paper, gas chromatography–mass spectrometry was used for qualitative and quantitative analysis of the seafloor geochemical anomaly; two comprehensive abnormal zones for oil–gas exploration were delineated in the northeast and southwest parts of the Chaoshan Depression, respectively. By analyzing the differentiation and fabric characteristics of hydrocarbon gases, as well as methane δ¹³C (‰), the underlying reservoirs are identified as gas reservoirs, and DS-A is predicted to be a gas-rich structure. Microfractures are the main controlling factors for the occurrence of microseepage, and gas microseepage causes the submarine geochemical anomaly on the top of oil and gas reservoirs. Submarine geochemical anomaly and underlying reservoir have a good associative relationship; it can be used to predict the oil and gas reservoirs accurately.

Shale oil and gas resources are considered one of the most important strategic resources globally today. However, the matrix permeability of oil shale reservoirs is extremely low, it requires modification through hydraulic fracturing technology to realize their economic and effective development. Against this background, we focused on the oil shale in the Xunyi area of the Ordos Basin, employing the ABAQUS platform to simulate and investigate the characteristics of hydraulic fracturing fracture propagation in fracture-developed oil shale reservoirs and the principal influencing factors. The results of the study show that the larger the angle between the natural fracture and the hydraulic fracture, the easier it is for the hydraulic fracture to pass through the natural fracture; the larger the elastic modulus of the matrix, the stronger the ability of the fracture to penetrate through the stratum, and the fracture morphology tends to be more narrow and long. The direction of fracture propagation tends to be in the direction of the geostress difference, and with the increase of the geostress difference, the degree of convergence of the direction of fracture propagation and penetration is greater. The higher the viscosity of the fracturing fluid, the wider and shorter the fracture tends to be, but it has minimal impact on the direction of fracture propagation. Increasing the fracturing fluid displacement can increase the fracture width and length and enhance the effect of the hydraulic fracturing modification. The research results are significant for the optimized fracturing design in oil shale reservoirs.

The barite of the Jbel Irhoud deposit in Western Jebilet, Morocco, is a Paleozoic massif known for its mineralization, which occurs mainly in shale, sandstone, and Middle Cambrian limestone. Three main types of barite deposits are known in the area: karst, vein fillings, and limestone replacement. The karst formations make up the majority of the reserves. Barite-quartz-galena and Fe-Cu-Zn- and Ag-sulfides, as well as hematite-carbonates, form the mineral paragenesis. Oxidation and mixing models are proposed for the deposition of barite. To check the effects of oxidation, numerical modeling of aqueous fluid composition for Irhoud barite deposition (at 150°C–250°C, Psat, and 1–6 m NaCl) was performed using a program developed by Professor Moine at the Paul Sabatier University in Toulouse, France. It shows that a large amount of barium can be transported as Ba²⁺ (barium chloride becomes more significant at relatively high temperatures) and that the decrease in solubility of barium under the given conditions can be caused by an increase in fO2, with or without a decrease in temperature, pressure, and/or salinity. Moreover, it is shown that the mixing of two fluids with different compositions leads to an oxidation (and a partial decrease in temperature) that causes a significant decrease in the solubility of barium (more than 130 ppm) and thus an efficient precipitation of barite in the Jbel Irhoud deposit. This modeling could be used to explain the manifestation of fluids with different compositions associated with the deposition of barite worldwide. The hydrothermal and structurally controlled Irhoud barite is the result of rapid decompression and Ba²⁺/BaCl⁺ transport under moderate to high P–T conditions, suggesting an epigenetic, postsedimentary system.

The creep of rock is a complex mechanical phenomenon driven by internal stress adjustment and the interplay between hardening and damage effects. To precisely capture the nonlinearity of rock creep and the law of accelerated deformation, a hardening function and a damage variable are introduced. Based on traditional rheological models, creep mechanisms, and damage laws, an accelerated creep constitutive model integrating hardening and damage effects is established. This model uses nonlinear functions and physical parameters to describe the coupling of hardening and damage throughout the creep process. The results show that the model can accurately reproduce the entire creep curves of rock specimens under different stress levels, with correlation coefficients exceeding 0.90. Further verification with diverse test data confirms its ability to describe the whole creep process and reflect the hardening–damage mechanisms, enabling accurate prediction of the transition to the failure-prone tertiary creep stage. Overall, this constitutive model provides a more accurate theoretical tool for understanding rock creep, offering significant value for rock engineering design and stability analysis in projects like underground mining and tunneling.