Fracture Density Research Articles

Optimization method for predicting coal reservoir fractures in the Laochang area of Eastern Yunnan using paleotectonic stress inversion

IntroductionCoal reservoir fractures serve as critical storage spaces and migration pathways for coalbed methane (CBM), significantly influencing CBM enrichment. The characteristics of coal reservoir fracture development can be obtained using traditional simulation methods, but these still have shortcomings. This work presents an optimization approach for the traditional method.MethodsThis study introduces an optimization approach for traditional methods with two novel contributions. This study integrates the simulation of tectonic stress fields with fracture prediction, using surface sandstone fractures as constraints to reconstruct the paleostress field of the coal seam, while also accounting for the influence of coal thickness on fracture development to calculate fracture density.ResultsThe predicted fracture density results were validated against measured values from the Bailongshan mine and Xiongdong coal mine with a relative error of approximately 12%, suggesting a reasonable degree of reliability.DiscussionBased on the results of the fracture simulation predictions, it is believed that the coal seam fracture density in the study area is mostly 10–20 lines/m and that the sweet spot for CBM development is located in the Yuwang block.

Experimental investigation on fracture propagation in shale fractured by high-temperature carbon dioxide

The productivity of shale reservoirs was significantly enhanced by the high-temperature CO2 fracturing technique. The injection of high-temperature CO2 into the formation induced rock fracture propagation, creating advantageous pathways for fluid flow. In this research, a self-developed in situ high-temperature convective heat simulation experimental apparatus was employed to systematically conduct simulated experiments on high-temperature CO2 fractured shale under different influencing factors. The experimental results demonstrated that the permeability of CO2 increased as the injection temperature increased. The rock fracture pressure was effectively reduced by high-temperature CO2 fractured shale. Higher complexity was observed in fracture propagation, accompanied by a substantial increase in microcracks and branching fractures. The shale fracture pressure increased with increasing triaxial stress and CO2 injection rate. The confining pressure restricted the further propagation of fractures under relatively high stress conditions, thereby reducing the width and density of fractures, lowering the fracture complexity. Nevertheless, the thermal shock effect of the fluid was exacerbated as the injection rate of high-temperature CO2 increased. The initiation of microcracks was facilitated by the intensification of local thermal stress in shale, inducing multiple curved fractures and forming a more complex fracture network. Compared to horizontal bedding shale, the fracture pressure of vertical bedding shale was relatively higher during high-temperature CO2 fracturing. In addition, the geometric morphology of fracture propagation was more complex, characterized by rougher fracture surfaces, leading to a greater improvement in reservoir reconstruction volume. This research contributed to the optimization of CO2 resource utilization, provided experimental evidence for the application of high-temperature convection fracturing technology in in situ shale conversion projects.

Exogenous Opioids and the Human Endocrine System: An Endocrine Society Scientific Statement.

The use and misuse of opioids are a growing global problem. Although the effects of these drugs on the human endocrine system have been studied for decades, attention on their related clinical consequences, particularly on the hypothalamic-pituitary system and bone health, has intensified over recent years. This Statement appraises research data related to the impact of opioids on the gonadal and adrenal function. Whereas hypogonadism is well recognized as a side effect of opioids, the significance of their inhibitory actions on the hypothalamic-pituitary-adrenal system and the occurrence of clinically relevant adrenal insufficiency is not fully elucidated. The often-inconsistent results of studies investigating how opioids affect the secretion of GH, prolactin, arginine vasopressin, and oxytocin are assessed. The accumulating evidence of opioid actions on bone metabolism and their negative sequelae on bone mineral density and risk of fracture are also reviewed. In each section, available data on diagnostic and management approaches for opioid endocrine sequelae are described. This Statement highlights a plethora of gaps in research associated with the effects and clinical consequences of opioids on the endocrine system. It is anticipated that addressing these gaps will improve the care of people using or misusing opioids worldwide. The Statement is not intended to serve as a guideline or dictate treatment decisions.

Optimising Neural Networks for Enhanced Fracture Density Prediction in Surrounding Rock of Coalbed Methane Reservoir

ABSTRACTFractures influence the mechanical strength of coal roof and floor, constraining the design of hydraulic fracturing for coalbed methane production. Currently, the predominant approach involves the integration of petrophysical logging with machine learning for fracture prediction. Nevertheless, challenges exist regarding the model's accuracy. In this study, we present a novel approach to predict fracture density. Our method optimises a back‐propagation (BP) neural network and utilises principal component analysis for feature extraction. We employ logging parameters (density, compensated neutron and acoustic time difference) obtained from Shouyang Block well SY‐1 and fracture density data from electrical imaging logging to construct the FVDC model's dataset. The BP neural network model is optimised using the Sparrow Search algorithm and Tent Chaotic Mapping. The results demonstrate a substantial enhancement over the BP neural network model, with reductions of 80.102% in mean absolute error, 94.182% in mean square error, 75.879% in root mean square error and 79.764% in mean absolute percentage error. When considering accuracy, the optimised model (97.098%) surpasses the support vector regression model (96.478%), the random forest model (94.404%) and the BP neural network model (85.657%). Scalability testing for the optimised model was conducted using data from well SY‐2, yielding a remarkable prediction accuracy of 96.775%. This performance exceeds that of the BP neural network (with an accuracy of 85.102%), as well as the random forest and support vector regression models (with accuracies of 91.234% and 90.384%, respectively). These results underscore the potential of well logging and machine learning in FVDC prediction.

Integration of Geological Model and Numerical Simulation Technique to Characterize the Remaining Oil of Fractured Biogenic Limestone Reservoirs

AbstractFine geological modeling leads to accurate reservoirs numerical simulations. Fractured biogenic limestone has abundant storage spaces and flow paths to accumulate oil and gas. The complexity and diversity of fractured biogenic limestone also lead to challenges in accurately characterizing its pore volume and remaining oil. This investigation aimed to enhance the understanding of fractured biotite reservoir properties via geological modeling. Numerical simulations were used to characterize the remaining oil during the late stage of field development. Considering the differences in porosity and permeability between fractures and matrix, a facies-controlled stochastic modeling technique was used to establish a dual-porosity and dual-permeability (DPDP) model for numerical simulation. Core information, logging data, and multiple seismic attributes were combined to guide low-level sequence fault interpretation for tectonic refinement. Based on classified seismic inversion, sedimentary phases were reconstructed. A discrete fracture network (DFN) model was obtained based on fracture occurrences and density models. The optimized discrete adjoint (ODA) algorithm was utilized to calibrate model parameters. The findings revealed that dense tectonic fractures develop in thick biogenic limestone areas. Combined with advanced reservoir simulation technology, these findings suggest that areas of thicker biogenic limestone were consistent with areas of higher fracture matrix conductivity multipliers. The remaining oil distribution patterns were investigated, and to deploy new wells was guided. Therefore, it is essential to better understand the tectonic characteristics of fractured biogenic limestone reservoirs and their remaining oil distribution patterns by integrating multiple sources of information and mastering advanced reservoir simulation technology for oilfield development.

Faulted karst reservoir spaces in Middle-Lower Triassic carbonates, Qingjiang Region, Yangtze block, China

The complexity and heterogeneity of ultra-deep faulted karst reservoirs pose significant challenges for hydrocarbon exploration. In this study, we integrated remote sensing image analysis, field measurements, and core sample testing to evaluate the characteristics and controlling factors of carbonate reservoir spaces within the Middle and Lower Triassic formations along a regional strike-slip fault in the Qingjiang region of China. The strike-slip fault zone is composed of multiple fault cores and damage zones. Based on differences in damage zone width and linear fault density, the fault zone was subdivided into transtensional and transpressional segmentations. The carbonate reservoirs, primarily developed within the damage zones, consist of fractures, fracture clusters, and cavities. Detailed measurements of the carbonate outcrops were conducted to obtain geometric parameters of the reservoir spaces. Quantitative results indicate that in the transtensional segmentation, the reservoir is dominated by tensile fracture-cavity systems, characterized by larger fracture apertures (0.13–1.25 m), higher linear fracture density (0.38–8.37 m⁻1), and well-developed cavities (0.03–4.84 m2), which contribute to better fluid connectivity and storage capacity. In contrast, the transpressional segmentation is dominated by compressional fracture-fracture cluster systems, with longer fractures (0.11–12.52 m), smaller fracture apertures (0.01–0.94 m), and extensive fracture clusters development (0.18–17.87 m2), but with lower fluid connectivity and limited storage capacity. Mechanical testing results show that the average compressive strength in the transtensional segmentation (133.95 MPa) is significantly higher than that in the transpressional segmentation (70.28 MPa). In terms of mineral composition, the transtensional segmentation has a higher calcite content, whereas the transpressional segmentation is richer in dolomite and quartz. Based on the observed differences in reservoir space characteristics across the strike-slip fault zone, we discussed the combined effects of structural segmentation, formation thickness, rock mechanics, and brittle mineral content on reservoir space development. The study emphasizes that stress conditions (primary factor) and material properties (secondary factor) jointly control fluid migration and storage efficiency in the reservoirs. Additionally, we suggest that the outcrop studies in the Qingjiang region provide valuable geological analogs for faulted karst reservoirs, offering critical insights for improving the precision of carbonate reservoir exploration and optimizing production efficiency.

Comparison of Torsional and SH Waves in Isotropic and Anisotropic Media Based on Laboratory Measurements

Abstract Utilization of the torsional wave signal has been reported in medical testing and engineering detection. A torsional wave is a shear-wave train whose vibrating direction (polarization) forms a torsional motion. However, there are a lack of understanding of its characteristics and potential for subsurface investigations. Here, compressional (P), shear (S) and torsional (T) transducers are constructed using different piezoelectric-transformer (PZT) chips in the laboratory and the characteristics of the torsional (T) wave propagating in isotropic and fracture-induced anisotropic media are analyzed in line with conventional P- and S-waves, covering waveform, amplitude, arrival time and velocity at different propagating angles. The results indicate that the velocity and anisotropy values measured using the T transducer are almost the same as the SH wave. For propagation in isotropic and anisotropic media, the wavefield generated by the T transducer is very simple with no mode conversions and source-generated interferences, which is similar to the SH wavefield, whilst the SV wavefield comprises of a series of complex events from mode conversions and interferences. For propagating in fluid- saturated fractured rocks, the torsional wavefield also comprises of a fast and slow wave train, which is referred to as torsional-wave splitting, and is similar to the shear wave splitting from S transducers. Furthermore, the anisotropy parameters measured using P, S and T transducer show a good correlation with the fracture density, and the P wave anisotropy is higher in air saturated rocks than water saturated rocks, while the shear wave anisotropy measured by S transducer and T transducer are sensitive to fracture density. Similar to the P transducer, the T transducer is polarization-independent, or directional invariant. Therefore, utilizing the T transducer may simplify the field logistics during 3D shear-wave surveys. However, field torsional wave generation is a major issue that needs further study.

Developmental characteristics of vertical natural fracture in low-permeability oil sandstones and its influence on hydraulic fracture propagation

Vertical natural fractures (NFs) are prevalent in low-permeability sandstone reservoirs. Presently, the impact of NFs on the extension of hydraulic fractures (HFs) remains partially unveiled, which restricts the scientific development of strategies for low-permeability, fractured oil sandstones. In this study, taking the oil sandstone of the He-3 Member, Hetaoyuan Formation, southeastern Biyang Depression as an example, we conducted a comprehensive investigation into the factors influencing vertical fracture development and the interaction between natural and hydraulic fractures. The cohesive unit simulations indicate that geostress is the principal factor influencing HF expansion, more so than NFs, with this influence intensifying as natural fracture density increases. As natural fracture density grows, the potential for two sets of conjugate natural fractures to form short HFs arises, which are limited in expansion scope, suggesting a need to reduce well spacing accordingly. Conversely, areas with a single set of NFs are more prone to developing longer HFs, warranting an increase in well spacing to avoid water channeling. High natural fracture densities may constrain the effectiveness of HFs. In fractured reservoirs with a 10 MPa horizontal stress difference, the length of HFs is 1.52 times that of HFs with 0 MPa and 5 MPa differences. However, the hydraulic fracture effectiveness index (FE) of the latter is 1.74 times higher than the former. For fractured reservoirs, the expansion capacity of HF length within a 5 MPa horizontal stress difference remains relatively stable; beyond this threshold, the expansion capacity increases with the growing horizontal stress difference, and the fracturing effect eventually deteriorates. Furthermore, as the strength of NFs escalates, the length and modified area of HFs initially decrease significantly before stabilizing. The complexity and FE value of HFs formed under strong natural fracture conditions are heightened, indicating a more effective fracturing outcome.

Integration of 2D and 3D electrical resistivity tomography and 2D gravity modeling to evaluate groundwater investigations in the Burka Uke catchment area, western Ethiopia

The increasing demand for water resources due to the expanding infrastructure and growing population of Uke town, West Ethiopia, necessitates a comprehensive understanding of groundwater potential within the Burka Uke catchment. The aims and objectives of this study are to identify a map of the aquifer by characterizing the subsurface earth, basement rock depth, resistivity and density of geological layers, their thicknesses, and structural features. The investigation integrates electrical resistivity tomography and gravity modeling to delineate potential groundwater zones and their structural controls. Electrical resistivity tomography profiles (1, 4, and 6) revealed low resistivity zones indicative of potential aquifers. The significant resistivity contrast (378 to 1412 Ω.m) suggests a high fracture density, potentially enhancing groundwater storage. The Bouguer gravity anomaly map, separated into regional and residual components, displayed values ranging from 51.79 to 41.59 mGal, highlighting density variations in the subsurface. As a result, analysis of the residual gravity anomaly map identifies north–south striking fault elements, indicating their influence on groundwater flow.The combined 2D and 3D ERT data also revealed a 2D gravity model of the aquifer from which the concentration extended throughout the study area. Data validation with previously drilled wells has confirmed the effectiveness of the geophysical methods used in identifying potential groundwater zones. This study provided critical information for the sustainable management of existing groundwater and demonstrated the effectiveness of integrating geophysical techniques to delineate and characterize aquifers in water-stressed areas.

Microstructural response of coal fracture surface induced by ScCO2 injection measured with AFM

Fractures in coal serve as the principal channels for the migration of coalbed methane (CBM). The microscopic traits of coal fracture surface are of significance for evaluating reservoir permeability and directly influence the outcome of CO2 storage and displacement. To comprehend the impact of CO2 on the coal fracture surface, the alterations in the coal fracture surface before and after CO2 injection are investigated vis atomic force microscopy. As CO2 gradually transforms into a supercritical state, the fracture density and aperture on the coal fracture surface gradually escalate. The mean pore size and porosity of the coal fracture surfaces rose from 5.45 nm to 6.55 nm and from 4.66% to 6.85%, respectively. The proportion of micropores (<2 nm) gradually diminished. The proportions of mesopores (2∼50 nm) and macropores (>50 nm) proportions gradually. Swelling, extraction and mineral dissolution are the predominant reasons for the alteration in the pore structure of the coal fracture surface. CO2 injection modifies the roughness and fractal characteristics of the coal fracture surface. The mean roughness Ra dropped from 6.54 nm to 4.03 nm, and the fractal dimension Ds declined from 2.45 to 2.28. With the fixed scanning range, the injection of CO2 has been shown to reduce the roughness of coal fracture surface and lower their fractal dimension, thereby has a positive influencing permeability enhancement. Therefore, in CO2-ECBM engineering, it is essential not only to analyse the physical properties of the target reservoir, but also to conduct a comprehensive evaluation of permeability with a suitably defined area of the reservoir.

Research on Numerical Simulation Methods for Water Invasion Dynamics in Fractured Gas Reservoirs with Water Content

Abstract Fractured gas reservoirs with water have complex gas-water relationship, large permeability difference between matrix and fracture, complex gas-water percolation mode, rapid production decline, short stable production period and large reduction of recovery factor due to water production of gas wells, which poses great challenges to efficient development of gas fields. The fracture system is the main channel for the edge and bottom water channeling of gas reservoirs. It is the core issue to understand the water invasion dynamic characteristics of such gas reservoirs to accurately depict the fracture geometry occurrence and truly simulate the gas-water two-phase flow mechanism in the fracture-matrix dual media. Taking the Jia-2 gas reservoir in Moxi gas field as an example, a discrete fracture model construction method that explicitly characterizes the fracture system is proposed. Based on the discrete fracture model, a mathematical model of gas-water two-phase flow in the fracture-matrix dual system is constructed and numerically solved. The influence mechanism of fracture opening, length, density and occurrence on the water invasion performance of multi-layer gas reservoirs is discussed, and the main control factors of the water invasion and water channeling law of fractured water gas reservoirs are identified. The application shows that the water invasion dynamics of gas reservoirs based on the discrete fracture model are more consistent with the actual conditions of the mine, providing a theoretical basis for deepening the understanding of water invasion dynamics of this type of gas reservoirs, optimizing the gas well working system, and formulating targeted water control countermeasures..

The impact of effective fractured rock mass properties on development of flow channeling in enhanced geothermal systems

Controlling the distribution of working fluid in an Enhanced Geothermal System (EGS) is crucial to prevent early thermal breakthrough and sustain the initial heat drainage area. Over time, working fluid flow may localize to a small area if fracture permeability increases non-uniformly, and efforts are not made to control the flow distribution. This scenario can potentially lead to mechanical reopening of hydraulic fractures, flow channeling, and thermal short-circuiting. However, current models neglect the nonlinear and inelastic deformation of fractured rock masses on EGS coupled thermo-mechanical response. The objective of this work is to estimate and predict the likelihood of thermal short-circuiting by flow-channeling in an EGS reservoir composed of rock and compliant natural fractures. We utilize three dimensional numerical solutions with reservoir properties based on effective medium theory of fractured rocks to achieve this objective. The results show that presence of natural fractures considerably changes the EGS response to thermal destressing, compared to linear poroelastic models. Flow channeling and short-circuiting, resulting in early thermal breakthrough, are more likely to occur in sparsely fractured reservoirs with stiff and strong natural fractures. Conversely, short-circuiting is unlikely in densely fractured reservoirs where thermal strains are absorbed by natural fracture opening and shear sliding rather than by rock matrix contraction. Estimation of natural fracture density is crucial in long-term forecasting and prediction of EGS power output. Accurate fracture characterization could decisively impact the fate of a project.

Study on the deployment of differentiated well patterns for shale gas in southern Sichuan region

Shale gas blocks are of great geological differences in southern Sichuan, deploying differentiated well patterns accordingly is therefore significant. For two typical shale gas blocks in southern Sichuan, Dingshan normal pressure area and Yongchuan south area, a hydraulic fracturing interlayer law model based on the cohesive zone model and a fracture extension model based on rock damage theory were established. Hydraulic fracture height and length charts under different natural fracture density and operation parameters were drawn. Using these charts, fracture parameters in different areas were determined, and hydraulic and natural fracture models were established. By coupling an embedded discrete fracture model with geological models and fracture models, a complex fracture network simulation model was built to predict gas production. Horizontal well spacing, orientation, and length were optimized under different geological characteristics to maximize production and economic indicators, and a differentiated well pattern deployment strategy was proposed. Results show that, firstly, for Dingshan area, the fracture height range is 40-64 m with an average of 51 m, that of Yongchuan is 42-65 m with an average of 53 m. The fracture length range of Dingshan area is 215-350 m with an average of 300 m, whereas that of Yongchuan is 290-350 m with an average of 330 m. The optimal horizontal well spacing in Dingshan area is 300 m, the optimal well orientation is 60°-90°, and the optimal lateral length is 2000 m; and those of Yongchuan are 300 m, 90°, and 1680 m. Well pattern on-site can be adjusted according to the optimal parameters to achieve higher Estimated Ultimate Recovery (EUR) and Net Present Value (NPV).

Disturbance shear fracturing process and failure precursors of intermittent structural planes with different connectivity under true triaxial condition

The mechanisms, processes, and precursors of shear failure in rock structural planes under three-dimensional geostress and excavation disturbances are unclear, which poses challenges for disaster prediction and warning in underground rock engineering. Therefore, this study self-developed a new separation rolling-sliding shear device for rock structural plane under true triaxial condition, and proposed a true triaxial shear testing method to simulate the damage of rock structural plane induced by the three-dimensional geostress redistribution during engineering excavation and subsequent dynamic disturbance further triggering failure. True triaxial disturbance shear tests were conducted on intermittent structural planes with different connectivity. With connectivity increasing, disturbance shear strength and failure surface roughness of structural planes gradually decreases. An improved simplex acoustic emission spatial localization method was proposed to reveal disturbance shear fracturing evolution. During disturbance shear fracturing process, micro-tensile cracks dominate, and the proportion of micro-shear cracks continues to increase, showing a mixed tensile-shear fracture mechanism. Approaching to disturbance shear failure, the acoustic emission fractal dimension decreases rapidly then increases to the maximum value, the b-value decreases rapidly to less than 1, the rapid increase in LgN/b exceeds 3, and the low-frequency and high-amplitude dense fracture signal appears abundantly, which can be used as disturbance failure precursors of intermittent structural planes.

Assessing fragmentation and potential sliding zones in rock tunnels via computer vision technology

During the excavation of rock tunnels, accurately understanding the structural characteristics of the tunnel face is crucial for ensuring construction safety. The study evaluates the structural characteristics of the tunnel face by precisely characterizing and analyzing parameters like fracture trace length and dip angle, aiming to calculate the degree of fragmentation and potential sliding zones of the rock mass. In evaluating rock fragmentation degree, the study identifies and quantifies fracture trace lengths as a single-factor indicator to assess the fragmentation of the rock mass on the working face. By comparing with the p21 index, the reliability and reasonableness of the rock fragmentation evaluation are discussed. For the evaluation of potential sliding zones, a method for approximating the extraction of fracture traces is proposed. The assessment is then conducted based on multi-factor indicators, including fracture dip angle and length. Additionally, the advantages and disadvantages of various indicators under different calculation methods are discussed. The study finds that rock fragmentation indicators offer a more detailed and accurate description of the actual fracture density of the rock mass compared to the P21 index, proving to be generally more reliable under extreme conditions. Furthermore, the evaluation of rock fragmentation and potential sliding zones on the rock face can provide important references for the refined extraction of rock mass structural characteristics, ensuring the safe construction of tunnels.

Shale Reservoir Rock Physics Modeling and “Sweet Spot” Prediction Based on Digital Core

Abstract With the increasing advancement in shale exploration and development, the complex pore structure and organic-rich characteristics of shale have gradually become the focus of rock physics models. This study combined digital core technology to obtain detailed information on the shale mineral composition, content, pore and crack contents, and composition. The isotropic self-compatible approximation (SCA) model was used to couple the shale minerals and hard pores to construct a brittle mineral framework. The VRH model was used to mix kerogen and clay, and the SCA-DEM (differential equivalent medium) model was used to add organic pores to construct a clay-organic matter mineral framework. The anisotropic SCA model treated the clay-organic matter mineral framework as an inclusion added to the brittle mineral framework to construct the shale mineral framework. The Eshelby–Cheng model was used to add fracture to the mineral framework and establish a physical shale model. This model was used to optimise the selection of sensitive elastic parameters for physical properties such as brittle mineral and kerogen content, fracture density, and porosity, and the optimisation results were combined to construct an explanatory quantity template. In addition, according to actual data from a study area in southwestern China, we combined to the interpretation chart established by the model to perform isotropic inversion. Then, we analyzed and interpreted the brittleness index (BI) and total organic carbon (TOC) content of the reservoir and predicted the sweet spot area of the shale reservoir.

Hydraulic fracturing in the overpressured, isotropically stressed Cane Creek Unit, Paradox Basin

The Cane Creek Unit within the Paradox Basin is an unconventional oil play that poses substantial geomechanical and hydrological challenges. With hundreds of millions of oil barrels in place, this resource is a viable target, but a greater understanding of the subsurface geomechanics is required for more reliable and consistent production. We analyzed a previous hydraulic stimulation of the State 16-2 well, located in the northern part of the basin, to produce recommendations for how future stimulations might be improved. Specifically, we look at three components of the completed stimulation: 1) Spatial correlations of various well logs to identify regions favorable for retaining hydrocarbons within natural fractures; 2) Analysis of pressure-time data from the hydraulic fracturing stages during well stimulation to assess the complexity of the fracture networks; and 3) Evaluation of poroelastic effects from reservoir depletion to assess the potential for future restimulation. Results of our analysis provide quantitative insight about the State 16-2 stimulation and yield specific recommendations. The most important recommendation is to stimulate regions with an intermediate fracture density due to their ability to retain hydrocarbons. Restimulation, if needed, may be more effective if completed after significant depletion due to poroelastic stress changes. While the direction of maximum horizontal stress is a critical factor, it might be less crucial if restimulation is conducted after considerable reservoir depletion.#xD;

Nubian aquifer linkage to the High Aswan Dam Reservoir: Initial assessments of processes and challenges

Egypt, relying heavily on the Nile as its primary water resource, is facing a rising water budget deficit due to increasing consumption, hydroclimatic changes, and upstream river damming. To address the above, innovative management of High Aswan Dam Reservoir (HADR), the third largest artificial reservoir on Earth, and its exchange with the surrounding groundwater system is suggested to develop new agricultural areas. However, the interconnectivity mechanism between the HADR and the fossil Nubian aquifer, the largest transboundary aquifer in Africa, remains speculative due to the lack of in-situ investigations. To address this deficiency, we perform a geophysical survey using aeromagnetic, time-domain electromagnetic, and vertical electrical resistivity sounding in a 330 km2 pilot area to the northwest of the HADR that is hypothesized to have a dense fracture system that could act as a conduit between these two large water bodies. Our survey results show the presence of normal faults cross the reservoir to the tangential basement and the sedimentary cover that are water-saturated and act as recharges to the Nubian fossil aquifer. These in-situ investigations confirm previous orbital gravity observations by GRACE-FO hypothesizing the interconnectivity between the reservoir and the Nubian aquifer, which was subject to debate. We suggest that such connecting areas between these two water bodies can be optimal sites for future agricultural development using improved management of surface water-groundwater exchanges for irrigation. Finally, our findings highlight upcoming challenges for this linkage if the level of HADR reaches below ∼160 m above mean sea level (amsl) due to upstream dam operation during the Nile’s extended drought periods. Under these conditions, the Nubian aquifer could discharge back into the HADR at the investigated site, changing the water budget of the aquifer and compromising the planned agriculture developments in the adjacent areas, which account for ∼ 10 % of the total arable land in Egypt.

Viability of fracture characterization using seismic attributes through seismic physical modeling

Abstract Seismic attributes have been widely utilized for fault detection; however, accurately characterizing mesoscale fractures (1/10 to 1/4 wavelength) using these attributes remains challenging, particularly in complex geological setting. To explicitly reveal the effectiveness of seismic attributes in fracture characterization, we constructed a realistic physical model based on the stratigraphic structure of a real shale-gas play. This model incorporates several faults and six fracture zones containing vertically aligned mesoscale fractures of varying fracture densities, embedded in a target layer of 40 m equivalent thickness. Through a comprehensive evaluation of various seismic attributes, we demonstrate that, while these attributes effectively map faults or macroscale fractures, they are less reliable for characterizing mesoscale fractures. Although mesoscale fractures induce anomalies in seismic amplitude and attributes, the magnitude of these anomalies does not correlate with the fracture density. To address this limitation, we introduce the amplitude at the dominant frequency (ADF) attribute, designed to characterize fracture density in thin-beds with mesoscale fractures. A strong relationship is observed between fracture density and the ADF attribute, with a correlation coefficient of 0.8067. Thus, the ADF attribute serves as a valuable tool for interpreting seismic data in the context of mesoscale fracture density.

Control and prediction of bedding-parallel fractures in fine-grained sedimentary rocks: A case from the Permian Lucaogou Formation in Jimusar Sag, Junggar Basin, Western China

The fine-grained sedimentary rocks have numerous bedding-parallel fractures that are essential for the migration, enrichment, and efficient development of oil and gas. However, because of their variety and the complexity of the factors that affect them, their spatial prediction by the industrial community becomes challenging. Based on sample cores, thin sections, and well-logging and seismic data, this study employed a multi-scale data matching approach to quantitatively predict the development of bedding-parallel fractures and investigate their spatial distribution. Bedding-parallel fractures in the Lucaogou Formation in Jimusar Sag frequently occur along preexisting bedding planes and lithological interfaces. Unfilled bedding-parallel fractures inside or near source-rocks exhibit enhanced oil-bearing capacity. They were identified on micro-resistivity scanning images by the presence of regularly continuous black or nearly black sinusoidal curves. Overall, the developmental degree of bedding-parallel fractures was positively related to the brittle mineral and total organic carbon contents and negatively related to single reservoir interval thickness. The maintained porosity of the reservoir matrix contributed to a thorough response to factors affecting the development of bedding-parallel fractures. Here, an effective and objective method was proposed for predicting the development and distribution of bedding-parallel fractures in the fine-grained sedimentary rocks. The method was based on the matched reservoir interval density, reservoir interval density, and matched sweet spot density of bedding-parallel fractures. The prediction method integrated the significant advantages of high vertical resolution from logging curves and strong lateral continuity from seismic data. The average relative prediction error was 8% in the upper sweet spot in the Lucaogou Formation, indicating that the evaluation parameters for bedding-parallel fractures in fine-grained sedimentary rocks were reasonable and reliable and that the proposed prediction method has a stronger adaptability than the previously reported methods. The workflow based on multi-scale matching and stepwise progression can be applied in similar fine-grained sedimentary rocks, providing reliable technological support for the exploration and development of hydrocarbons.