Geofluids最新文献

It is one of the important disasters faced by coal mine that roof energy accumulation leads to its advance failure and roadway failure. Identifying the position of roof energy accumulation can predict the position of roof advance failure and roadway deformation, so as to take preventive measures. Based on two generalized displacement beams, the accumulation law of the bending moment and energy density of the top coal wall under different loads, different thicknesses, and different cantilever lengths is investigated. The following conclusions are drawn: (1) Under different load conditions, the peak of the bending moment and energy density both appear at 10 m in front of the coal wall and rapidly decrease to 0 after reaching the peak and no longer change. The peak value of the bending moment increases linearly with the increase of the load, and the relation is M = −143.32q − 286.63. The peak value of bending moment changes exponentially with the increase of load, and the relation is U^e = 200.46e^0.42q. (2) Under different thicknesses, the bending moment of the thickness to the rock layer has an irregular distribution at the peak value. When the thickness is 12.5 and 15 m, the change tends to be consistent, and when the thickness is 7.5 and 10 m, the bending moment of the roof is small when the thickness is 17.5 m. When the thickness is less than 17.5 m, the smaller the thickness is, the larger the peak value is, and the more advanced the peak value is. The smaller the thickness of the roof, the smaller the range of energy density accumulation. (3) Under different cantilever lengths, with the increase of cantilever length, the peak bending moment presents a linear increase, and the relationship is M^e = −158.22 L + 137.4, and the range of bending moment accumulation increases with the increase of the roof cantilever length. With the increase of the cantilever length, the peak energy density of the roof increases exponentially, and the relationship is U^e = 3.5536e^1.1067L, and the lead energy accumulation distance of the roof increases. (4) When the thickness of the roof is 10 m, the stress peak occurs more frequently within 5–15 m in front of the working face, which well confirms the correctness of the theoretical analysis.

In deepwater drilling, due to the complex coupling mechanism between the wellbore and the formation, the breathing effect is easily induced. The formation of the breathing effect is closely related to the unstable flow between the wellbore and the opening–closing formation fractures. The breathing effect refers to the phenomenon where a portion of the drilling fluid enters the formation fractures during circulation and returns after circulation stops. Its characteristics are similar to those of a well overflow. However, confusing the two can lead to extremely serious consequences due to incorrect handling. Currently, research on the coupled wellbore–formation flow mechanism and the induced breathing effect is still limited, highlighting the urgent need for more refined techniques to identify the breathing effect. To address this issue, a numerical model of the wellbore breathing effect was established by combining the wellbore unsteady flow model and the fracture deformation model. This model comprehensively considers the effects of flow resistance, fluid compressibility, flow path expansion, fracture deformation, and the equivalent damage radius. The model was applied to a subsalt well in the deepwater region of Mexico, and the results showed that the model’s accuracy had an error of less than 10% compared to the field data. Simulations were conducted to analyze bottomhole ECD changes, mud loss during pump start, and mud backflow during pump stop under varying flow rates, which improved the accuracy of identifying the formation breathing effect. This study provides guidance for accurately identifying the breathing effect in the field.

As one of the clean renewable energy sources, geothermal energy has broad prospects, and correctly understanding its genetic mechanism and resource reserve is the basis for the efficient utilization of the geothermal resources. The characteristics of the ground temperature field in the Pingdingshan mining area are analyzed, and the influence of groundwater convection in the Karst layer on the formation temperature was carried out by the hydrothermal coupling. In addition, the Monte Carlo method is adopted to reduce the uncertainty of input parameters. Results show that the geothermal field distribution shows obvious zoning characteristics, and the hydrothermal coupling simulation shows that the water-conducting fault can profoundly change the distribution of formation temperature, which is the boundary for the decline or rise of formation temperature. The thermal refraction effect caused by the fluctuation of bedrock is the main reason for the high temperature in the structural uplift area of the mining area, which is the heat flow disturbance caused by the thermal refraction effect within 12.3 mW/m². The heat contained in geothermal resources is (5.037 ~ 15.82) × 1014 J, while the heat contained in geothermal water is (0.8806 ~ 6.531) × 1014 J, and the rest is contained in the rock matrix.

Qadri, Hamza Azam, Ali Wahid, Numair Ahmed Siddiqui, Syed Haroon Ali, Ahmed Abd El Aal, Amirul Qhalis Bin Abu Rashid, and Mohd Najib Bin Temizi. “Prospect Analysis of Paleocene Coalbed Methane: A Case Study of Hangu Formation, Trans-Indus Ranges, Pakistan.” Geofluids 2022, no. 1 (2022): 8313048, https://doi.org/10.1155/2022/8313048.

The authors wish to correct the acknowledgement statement as follows, to acknowledge the support from Group Research and Technology (GR&T):

The authors would like to thank Universiti Teknologi PETRONAS, Malaysia, for the lab analysis and technical support at the Geoscience Department and research fund YUTP-FRG 1/2021 015LC0-363. We would also like to thank GR&T (Cost Centre: 015MDO-068) for some laboratory analysis support. Moreover, special thanks are due to the Makarwal Collieries Limited, Pakistan, for allowing access to their mines and to conduct this research work. The laboratory facilitation provided by the Center of Coal Technology, Punjab University, Pakistan, and Centralized Resource Laboratory (CRL), University of Peshawar, Pakistan, are also highly appreciated.

As GR&T is a commercial entity, the Conflict of Interest statement is therefore also corrected as follows:

Support for laboratory analysis was provided by GR&T. The authors declare no other conflicts of interest associated with this study.

The Dengying Formation within Pengtan 1 well area in the Sichuan Basin is a vital gas reservoir for exploration and development. The reservoir is situated in a complex fault block structure characterized by multistage fault evolution, leading to a complicated distribution of tectonic fractures crucial for the accumulation and migration of oil and gas. This study establishes a geological model to describe the fault patterns observed in the region and conducts numerical simulations of the paleotectonic stress field. Moreover, we combine rock fracture criteria and strain and surface energy theories to predict tectonic fractures quantitatively. Our findings indicate that the tectonic fractures in the study area predominantly consist of shear fractures, with primary development of low-angle and oblique fractures and, to a lesser extent, high-angle fractures. These fractures generally exhibit trends in the north–northwest (NNW), northeast (NE), nearly east–west (EW), and nearly south–north (SN) directions. Most fractures formed during the Yanshanian–Himalayan period are identified as effective fractures. The maximum and minimum principal stress values recorded for the Himalayan period of tectonic activity were 150–180 and 120–150 MPa, respectively. Faults significantly influence the distribution of tectonic stress, and stress concentration usually occurs near the fault. A significant correlation exists between tectonic stress and burial depth, exhibiting lower stress levels at shallower depths. In addition, the linear density of fractures gradually decreases from the fault core to its periphery and further decreases to areas far away from the fault. In these three regions, fractures mainly develop in the order of high angle, oblique, and low angle. This study enhances our understanding of the fracture dynamics within the Dengying Formation, contributing valuable insights into the region’s geomechanical properties and potential hydrocarbon exploitation strategies.

The northern Shanxi mining region, a pivotal coal-rich area in China, is characterized by substantial reserves of shallow coal seams and distinctive geological mining conditions that exacerbate overburden rock fissure development. This study delves into the mechanisms governing overburden damage and fissure evolution in shallow coal seams using the theoretical frameworks of key strata and mining subsidence, augmented by numerical simulation methodologies. It also examines the impact on ground fissure morphology and propagation. Additionally, this paper investigates the prediction of water-conducting fracture zone heights in shallow coal seams. This paper’s findings reveal a sequential dynamic process in overburden rocks during mining: microfissure initiation, key stratum rupture, fissure aggregation, and fissure coalescence. Leveraging a long short-term memory (LSTM) model, this paper develops a prediction model for water-conducting fracture zone heights in shallow coal seams, achieving high accuracy with a mean squared error (MSE) of 2.29, a mean absolute error (MAE) of 1.22, and an average relative error of 2.51%. These results contribute scientific insights for mitigating ground fissure disasters and facilitating ecological restoration in the context of intensive shallow coal seam mining in northern Shanxi. Furthermore, they hold substantial scientific merit in advancing the theories of mining subsidence and stratum control in mining engineering.

Drilling has shown that there is significant overpressure throughout the Jurassic in the central Junggar Basin and that the maximum pressure coefficient exceeds 2.0. The pore pressure in the central Junggar Basin was jointly predicted by combining a number of methods, such as the Eaton, Bowers, and equilibrium depth methods based on logging data, with the D_C method and Fillippone formula approach based on drilling and seismic interval velocity data, respectively. The findings indicate that, among the logging-based prediction methods, the Bowers method prediction of the pore pressure may more closely match the pore pressure. Based on seismic layer velocity data, the Fillippone approach can more precisely predict the change in section pressure by simulating pressure in space. The full forecast results show that two overpressure systems formed in the Jurassic system at Mbr. 1 (Badaowan) and Mbr. 3 (Xishanyao). The transfer of overpressured fluid also resulted in the development of localized overpressure in the Mbr. 2 (Sangonghe) and Mbr. 4 (Toutunhe) formations, which serve as transition zones of overpressure. The top interface of the overpressure section shows an increasing trend in burial depth from the deep concave to the slope region. The overpressure section also demonstrates outstanding low acoustic velocity characteristics. The Jurassic’s anomalous overpressure intensity decreased from the southwest to the northeast, and the overpressure gradient served as a dynamic mechanism for petroleum migration and accumulation.

The hydrocarbon-bearing property of a reservoir is a crucial index for its evaluation. Although various evaluation methods based on well-logging data can reasonably interpret the hydrocarbon-bearing property of most reservoirs, these methods often exhibit significant randomness and ambiguity. This is due to various external influences, making it challenging to quickly and accurately evaluate the hydrocarbon-bearing property of a reservoir. To address this issue, this study investigates the identification of hydrocarbon-bearing properties in reservoirs based on well-logging data and machine learning techniques. Initially, 1731 sets of well-logging data with hydrocarbon-bearing property identification result labels from 356 wells in the Shahejie Formation of the Bohai Bay Basin’s Qikou Sag were collected. The distribution of different hydrocarbon-bearing property categories was analyzed on three types of well-logging data: gas logging, quantitative fluorescence logging, and Rock-Eval pyrolysis. Subsequently, seven model inputs were formed by combining these three types of well-logging data, and their performance was evaluated in combination with three machine learning techniques: K-nearest neighbor, random forest, and artificial neural networks. The influence of different inputs and models on classification performance was compared. Lastly, the importance of each input feature was analyzed. The results showed that the combination of quantitative fluorescence logging and Rock-Eval pyrolysis as inputs with the random forest model could achieve the best classification performance, with a macro F1 score of 95.36%. This suggests that this method has sufficient precision for the identification of hydrocarbon-bearing property categories in formations, providing a more efficient classification method for the hydrocarbon-bearing property of reservoirs compared to manual identification.

During the excavation of the shaft, the inlet air temperature undergoes seasonal variations and is influenced by geothermal effects and air compression heat. Merely augmenting the inlet air volume fails to mitigate the extreme temperatures encountered at the deep working face. Consequently, the implementation of refrigeration and cooling technologies becomes imperative to manage the heat-induced issues. To address the high-temperature challenge during shaft excavation at the Sanshandao Gold Mine, a ventilation system model was developed utilizing Fluent simulation software. This model facilitated the prediction of the temperature field dynamics at the working face, taking into account project progression and seasonal shifts. Through a comprehensive analysis of factors encompassing cooling capacity deterioration, energy consumption for cooling, and the installation and maintenance requirements of refrigeration units across various systems, a surface-based centralized refrigeration system was devised. Furthermore, a simulation analysis was conducted to evaluate the refrigeration technology, offering valuable technical insights for the calculation of cooling capacity, as well as the selection and application of appropriate refrigeration systems. The results indicated that subsequent to excavating the shaft to a depth of 1600 m, the working face temperature fluctuated with seasonal variations but consistently remained above 28°C. At a depth of 1800 m, the temperature peaked, reaching a maximum of 40.19°C. Following the implementation of the surface centralized refrigeration system, with an inlet air volume of 22.6 m³/s and an inlet air temperature maintained below 10°C, the working face temperature was effectively reduced to below 27°C. This study presents a comprehensive suite of refrigeration and cooling methodologies, encompassing temperature field prediction, refrigeration parameter calculation, simulation analysis of cooling performance, refrigeration system design, and their application in deep shaft excavation. These methods provide a technical foundation for mitigating heat-induced damage in deep shafts.

There is an abundance of tight gas resources in narrow channel sand-bodies from the Jurassic Shaximiao Formation of the Jinqiu gas field in the central Sichuan Basin of China. The architecture of sand group in the study area is undefined, and the spatial distribution of channel sand-bodies is unclear. The complex and inhomogeneous sandstones have a significant impact on the reservoir’s physical properties and the fluid mobility of the reservoir. In this study, data from drilling cores, logs, seismic, and experiment testing were used to investigate the spatial distribution of sand group architecture and the channel types. There are five channel genetic types, including the multiphase superimposed type, deeply incised type, abandoned type, progradational superimposed type, and normal single genetic type. Based on the channel genetic types, the ratio of sandstone and mudstone, the ratio of width to depth, the connectivity ratio of sand-bodies, and the production dynamic characteristics, the channel sand-body connectivity is defined into three types. The connected sand-bodies occur in the multiphase superimposed and deeply incised types of channels, with an average connectivity ratio of 83%, a ratio of sandstone and mudstone larger than 0.9, and a ratio of width and depth larger than 40. Based on the association of sandstone and mudstone and rhythmic structure, the sand group architecture can be divided into three types, including (A) uniform-grain-sequence pure sandstone architecture, (B) positive-grain-sequence thick sandstone and thin mudstone architecture, and (C) positive-grain-sequence thick mudstone and thin sandstone architecture. There is a high content of natural gas in Types A and B of sandstones, with a daily gas production of 29.16 × 10⁴–47.6 × 10⁴ m³/day and pressure coefficients of 0.72–1.08. The sand group architecture of the study area is mainly controlled by the channel sinuosity and the ratio of accommodation and sediment supply, and Types A and B of sand group architectures occur with large channel sinuosity of 1.14–1.36 and a large ratio of accommodation and sediment supply of 0.61–2.92. Based on the connectivity degree of channel sand-bodies, the sand group architectures, and production data, the channels of the study area can be divided into three types. Type I channels mainly occur in Sand Groups 6, 8, and 9, and Type II and Type III channels occur in Sand Groups 6 and 7 in the western and southern parts of the study area. The technology of fine characterization for channel sand-bodies on the basis of human–computer interaction and seismic attributes is proposed, and geological modelling of the spatial distribution of sand group architectures and channel types is established. The research results achieve a theoretical breakthrough in the characterization of the sand-body structure of tight sandstone reservoirs in narrow river channels and assist in the efficient exploration and development o