Fracture Density Research Articles

Bayesian Fourier coefficient inversion for gravity-induced stress parameters in tilted transversely isotropic gas-bearing reservoirs

Field observations and core data reveal that natural fractures may not be perfectly vertical but are commonly inclined, yielding an effective tilted transversely isotropic (TTI) medium. Neglecting TTI symmetry can lead to erroneous stress prediction results, which are important for hydrocarbon exploration and development. We have developed a Bayesian Fourier coefficient (FC) inversion approach to estimate gravity-induced stress parameters in TTI media, specifically horizontal stress and the differential horizontal stress ratio (DHSR). The gas-bearing reservoir with dipping fractures is modeled as a linearly elastic, homogeneous TTI material. Under the assumption of no lateral strain, we combine fracture-effective medium models with the generalized Hook’s law to establish the relationship between gravity-induced stress parameters and TTI elastic and fracture parameters. Based on seismic scatter theory, we derive a linearized PP-wave reflection coefficient and corresponding FC expressions parameterized by P- and S-wave moduli, density, fracture density, and fracture dip in TTI media. Furthermore, we present a Bayesian FC inversion constrained by a joint multivariable Cauchy prior model to estimate these model parameters, which are then used to calculate gravity-induced stress parameters. A synthetic example demonstrates that Bayesian FC inversion under the TTI model assumption produces more reliable estimates of gravity-induced stress parameters compared to those obtained under the horizontal transversely isotropic (HTI) model assumption. Additionally, a real data set from a gas-bearing reservoir is employed to demonstrate the feasibility of our method. Results indicate that our method yields reasonable estimates of gravity-induced stress parameters with good lateral continuity. The proposed method could aid in identifying optimal zones for hydraulic fracturing of a subterranean formation with TTI symmetry.

Correlation Between Handgrip Strength and Bone Density and Fragility Fracture Risk Among Older Adults: A Cross-Sectional Study.

Population aging has led to a surge in elderly care needs worldwide. Bone aging, skeletal muscle degeneration, and osteoporosis pose critical health challenges for the elderly. The process of bone and skeletal muscle aging not only impacts the functional abilities but also increases fragility fracture risk. Although a negative correlation between handgrip strength and fragility fracture risk has been identified in elderly populations, there is a lack of related research in Taiwan. This cross-sectional study was designed to investigate the association between handgrip strength and two outcome variables, bone density and risk of fragility fracture, in Taiwanese individuals aged 65 years and older with low bone mass. A total of 548 older adults, including 84 men and 464 women, were recruited between August 2019 and July 2021. Bone mineral density T-scores acquired using dual-energy X-ray absorptiometry scan, the total score for the Taiwan-specific Fracture Risk Assessment (FRAX) tool, and bilateral handgrip strength acquired using a digital hand dynamometer were recorded along with other factors such as comorbidities, dietary habits, and daily activities. In this study, the mean age was 70.9 (SD = 5.6) years, mean bone mass index was 24.1 (SD = 3.5) kg/m2, mean FRAX main fracture risk score was 19.5% (SD = 8.3), and mean FRAX hip fracture risk score was 7.7% (SD = 5.7). Lumbar and hip T-scores were both significantly correlated with both dominant and nondominant handgrip strength in older woman. Older age; both lower hip and spine T-scores; both lower dominant and nondominant handgrip strengths; having Type 2 diabetes, coronary artery disease, or chronic hepatic disease; and lacking a steady job were significantly associated with a higher risk of fragility fracture. The results of this study provide important information regarding the correlation between handgrip strength and several variables, including bone mineral density T-score, FRAX score, comorbidities, and job status, among older adults. Notably, these correlations were found to be particularly strong in the female participants. This information may be used to facilitate the early identification of elderly individuals at a high risk of fragility fractures, enabling the timely development of preventive nursing strategies and the provision of targeted interventions.

Abrasive Layer Cracking Analysis and Strength Evaluation of High-Speed Grinding Wheels.

The design and production of high-speed grinding wheels should not only merely take into account their grinding performance but also their use safety. A batch of resin-bonded high-speed grinding wheels was manufactured through substrate grooving, gluing, and hot pressing. Abnormal cracking emerged between the abrasive layer and the substrate. To identify the cause of cracking, a series of physical and chemical analyses were employed to examine the cracked wheels. Fracture observation and density analysis indicate that different areas of the grinding wheels have a compact structure and uniform feeding. The hardness analysis reveals that the hardness of the cracked and uncracked areas is similar with no obvious distinction. The energy spectrum analysis demonstrates that no macroscopic foreign bodies remained on the bonding surface. The results of GC-MS, FTIR, DSC-TGA, and viscosity analyses indicate that the active ingredients of naphthol, 2-methyl-1-naphthol, and diphenol propane in the adhesive reacted or volatilized, leading to the alteration of the adhesive properties. Duplicate experiments show that the tensile strength of the old adhesive used in the failed batch is merely 11 MPa, which is significantly lower than the 65 MPa of the new adhesive. COMSOL simulation results suggest that the minimum bonding strength of the adhesive should not be less than 23.82 MPa to guarantee bonding between the substrate and the abrasive layer. The tensile strength of the old adhesive is insufficient to cope with the thermal stress generated during the forming and cooling processes of the grinding wheel, which is the root cause of the failure. The findings provide theoretical guidance for the upfront design, raw material control, and process control of high-speed grinding wheels, ensuring their safe use.

Predicting Transient Anomalous Transport in Two‐Dimensional Discrete Fracture Networks With Dead‐End Fractures

AbstractPollutant transport in discrete fracture networks (DFNs) exhibits complex dynamics that challenge reliable model predictions, even with detailed fracture data. To address this issue, this study derives an upscaled integral‐differential equation to predict transient anomalous diffusion in two‐dimensional (2D) DFNs. The model includes both transmissive and dead‐end fractures (DEFs), where stagnant water zones in DEFs cause non‐uniform flow and transient sub‐diffusive transport, as shown by both literature and DFN flow and transport simulations using COMSOL. The upscaled model's main parameters are quantitatively linked to fracture properties, especially the probability density function of DEF lengths. Numerical experiments show the model's accuracy in predicting the full‐term evolution of conservative tracers in 2D DFNs with power‐law distributed fracture lengths and two orientation sets. Field applications indicate that while model parameters for transient sub‐diffusion can be predicted from observed DFN distributions, predicting parameters controlling solute displacement in transmissive fractures requires additional field work, such as tracer tests. Parameter sensitivity analysis further correlates late‐time solute transport dynamics with fracture properties, such as fracture density and average length. Potential extensions of the upscaled model are also discussed. This study, therefore, proves that transient anomalous transport in 2D DFNs with DEFs can be at least partially predicted, offering an initial step toward improving model predictions for pollutant transport in real‐world fractured aquifer systems.

The propagation laws of hydraulic fractures under the influence of natural fracture zones

This paper uses the finite-discrete element method (FDEM) to establish a fluid–solid coupling model for the propagation of multi-cluster hydraulic fractures. The validity of the proposed model is verified using the analytical solution and onsite microseismic data. The results show that with the approach angle increases, the propagation of hydraulic fracture transitions from a single capture mode to the mixed modes of capture, crossing and blocking. The total length of hydraulic fractures is negatively correlated with the approach angle and cohesion of natural fracture, and positively correlated with the distribution density and bandwidth of natural fracture. The length of shear fractures initially increases and then decreases with the increase in approach angle, showing negatively, positively, and positively correlated with cohesion, length, and bandwidth, respectively, while the trend of tensile fracture length is opposite to it. The tortuosity of hydraulic fractures (which is used to characterize the complexity of fracture morphology) initially decreases and then increases with the increase in the approach angle, negatively correlated with the cohesion of natural fracture, and positively correlated with the distribution density and bandwidth of natural fractures. Comparatively, the fracture propagation morphology is the most complex at the approach angle of 45°, which is more conducive to full reservoir enhancement. Conversely, under conditions of high cohesion, narrow width, and low-density distribution of natural fractures, the fracture morphology is relatively simple, all of which are unfavorable for reservoir enhancement in the target segment.

Modeling the influence of bainite transformation on the flow behavior of steel using a macroscale finite element analysis

This study comprehensively investigates the kinetics of bainitic ferrite transformation in steel alloys by integrating experimental results, finite element analysis, and thermodynamic modeling. Using a dilatometer and Gleeble tests, empirical data were acquired to calibrate the Bhadeshia and Hensel-Spittel models, forming the basis for subsequent finite element simulations. Owing to the high importance of temperature in bainite transformation, the accuracy of the predicted temperature fields was validated precisely against experimental measurements, confirming the reliability of the methodology. A modified Bhadeshia model was proposed incorporating the influence of the applied shear stress on the activation energy, thereby emphasizing the temperature-dependent Cstress coefficient. The electron backscatter diffraction results validate the finite element model, and further exploration reveals the implications for fracture patterns and density changes due to bainitic transformation. This study contributes to a nuanced understanding of bainitic ferrite kinetics, offering valuable insights for alloy design and optimization under various thermomechanical conditions, and paving the way for advanced research on phase transformation kinetics and material behavior.

Quantitative estimation of three-dimensional fracture density: Insights from the stereological relationship between borehole and universal elliptical DFN

Quantitative estimation of three-dimensional fracture density: Insights from the stereological relationship between borehole and universal elliptical DFN

Determining Dhap Pokhari lake surface dynamics for restoration strategies through geoelectrical mapping

ABSTRACT Lakes in the hilly regions of the Sikkim Himalayas in India are crucial for water supply and tourism. However, this area experiences frequent earthquakes and microtremors, increasing the risk of seismic hazards and contributing to a higher density of subsurface fractures and discontinuities. This has led to water seepage in lakes across Sikkim, turning some from perennial to seasonal. To investigate these issues, geoelectrical mapping techniques, specifically Vertical Electrical Sounding (VES) and profiling, were used to study Dhap Pokhari Lake in Sikkim’s Pakyong district. The findings revealed a subsurface fracture zone beginning at a depth of 20 m and extending down to 50 m. The VES data showed significant variations in sediment thickness and subsurface lithology between two measurement points only 10 m apart, with a noticeable ground settlement of about 2 m at one location. The profiling results indicated a major fracture and two minor ones, which are likely causing water seepage and ground saturation, particularly during rainy seasons, leading to compaction and ground settlement. This poses a risk to the structural stability of the surrounding areas, highlighting the need for effective lake restoration strategies. Geoelectrical mapping is a valuable tool for identifying such subsurface fractures and making evidence-based strategies to revive lakes in this seismically active region.

Bibliometric Analysis of The 40 Years Literature On Vertebral Fractures With Science Mapping Method

Each year, over 1.5 million individuals in the United States are diagnosed with vertebral compression fractures. The concept of bibliometrics pertains to the analysis of bibliographic data. The examination and visualization of the literature within a scientific discipline or its subcategories is referred to as science mapping. This study represents a comprehensive analysis of the literature on vertebral fractures. In our research, the Web of Science database was utilized for analyses, encompassing the period from 1980 to 2022. The analyses were divided into four categories: performance analysis, keyword analysis, thematic analysis, and co-citation network analysis. Word Cloud, Frequency Table, Trend Topics, and Co-occurrence Networks were examined. Thematic Maps and Thematic Evolution Maps were also constructed. Furthermore, a co-citation network analysis of articles was conducted. The analyzed articles were authored by 9,020 researchers. The annual increase in the number of publications was recorded as 9.54%. The average number of citations per document was 44.05. Approximately 18.7% of the articles were published through international collaborations, with Europe standing out prominently in this regard. Genant HK was identified as the author with the highest h- and g-indices. The most active institution was the University of California, San Francisco. The most frequently used keywords included Vertebral Fracture, Osteoporosis, and Bone Mineral Density. Over the past 40 years, the scientific literature on spinal fractures has been analyzed through science mapping. The developmental dynamics of this field have been identified.

Characteristics of the Microfracture and Pore Structure of Middle- and High-Rank Coal and Their Implications for CBM Exploration and Development in Northern Guizhou

The microfracture and pore structure characteristics of coal reservoirs are crucial for coalbed methane (CBM) development. This study examines the evolution of pore and fracture structures at the microscopic level and their fractal characteristics, elucidating their impact on CBM development in the northern Guizhou coal reservoirs. The results indicate that the pores and fractures in the coal reservoirs are relatively well-developed, which facilitates the adsorption of CBM. The density of primary fractures ranges from 5.8 to 14.4 pcs/cm, while the density of secondary fractures ranges from 3.6 to 11.8 pcs/cm. As the metamorphic degree of coal increases, the density of primary fractures initially increases and then decreases, whereas the density of secondary fractures decreases with increasing metamorphic degree. With increasing vitrinite reflectance, the specific surface area and pore volume of the coal samples first decrease and then increase. The fractal dimension ranges from 2.3761 to 2.8361; as the vitrinite reflectance of the coal samples increases, the fractal dimension D1 decreases initially and then increases, while D2 decreases. In the northern Guizhou region, CBM is characterized by an enrichment model of “anticline dominance + fault-hydrogeological dual sealing” along with geological controlling factors of” burial depth controlling gas content and permeability + local fault controlling accumulation”. The research findings provide a theoretical basis for the occurrence and extraction of CBM in northern Guizhou.

Characterizing broad-band seismic dispersion and attenuation in carbonates with fractures and cavities: a numerical approach

SUMMARY Carbonates are highly heterogeneous and commonly develop large-scale fracture-cavity systems due to the strong diagenesis effect of dissolution, faulting and karstification. Understanding the seismic wave velocity and attenuation signatures is crucial for hydrocarbon exploration and recovery, carbon capture, geothermal exploitation and groundwater management using seismic methods. Nevertheless, due to the sample size limitation, traditional core-scale experiments and sonic logs fail to effectively unravel the essential factors controlling elastic and anelastic responses of those carbonates with large-scale heterogeneity. We developed a 2-D geology-constrained method for constructing digital rock models of carbonates with fracture-cavity systems, integrating outcrop data and statistical analyses. Using finite element simulations based on Biot's quasi-static equations of poroelastic consolidation, we examine the effects of cavity shape, size and number, as well as fracture number, length, width and angle, on wave dispersion and attenuation characteristics. Deep carbonate rocks with fracture-cavity systems exhibit wideband attenuation spanning over three orders of magnitude (from < 0.01 to >10 Hz), driven by coupled pore pressure relaxation mechanisms in the heterogeneous system. Horizontal attenuation was found to be roughly five times greater than vertical attenuation (as fractures are predominantly in a semi-vertical direction), highlighting significant attenuation anisotropy. While cavities have minimal effects on attenuation, fracture density and geometry—especially longer and narrower fractures—significantly influence wave dispersion and attenuation behaviour. These results underscore the importance of integrating both seismic velocity and attenuation data to enhance reservoir characterization reliability, and highlight the potential of using comprehensive broad-band seismic data and large-offset seismic data to improve geophysical interpretations of complex deep carbonate reservoirs.

Note on Dodgson’s Rock platform, Elkington quarry, and the origin of bornhardts on north-western Eyre Peninsula, South Australia

The excavation of what was Dodgson‘s Rock, now Elkington quarry, exposed a domical bedrock form that can be construed as a stage in the development of incipient bornhardts. It confirmed the earlier interpretation of the domical inselberg known as Ucontitchie Hill as a structural feature initiated by the differential etching in the shallow subsurface of compartments of granitic rock of contrasted fracture density and exposed by the erosional lowering of the densely fractured and weathered surrounds. Stages in the excavation provided evidence concerning the nature of sheet fractures and structures as well as the origin of breached arches or A-tents. Other bornhardts in the district (Mt Wudinna, Polda Rock, Little Wudinna Hill) as well as sundry additional inselbergs, turrets, and elevated platforms may be of a similar origin.

Evolution of the internal structure and physical properties of Tongxin sandstone under high temperature

The stability of the surrounding rock under high temperature is pivotal to the efficient and safe production of high-temperature fluidized mining engineering. To investigate the stability of rocks under high temperature, this paper takes the roof sandstone of Tongxin coal mine, examining changes in its physical parameters such as mass, dimensions, wave velocity, porosity, and permeability after treatment at various temperatures (20–700°C). The results showed that parameters like mass and wave velocity decreased with increasing temperature, while dimensions, porosity, fracture density, and permeability increased. The patterns of change in these physical properties with temperature exhibit a high degree of consistency. Additionally, composition analysis and thermal analysis were conducted to understand the physical and chemical changes occurred in sandstone. Scanning electron microscopy was used to observe microstructural changes in the sandstone. After analysis, the evolution of the internal structure of Tongxin sandstone with heat treatment is categorized into three stages. (1) stable change Stage (20–450°C, 650–700°C): Dominated by dehydration and thermal stress, where pore and fracture structures develop slowly; (2) rapid change stage (450–550°C, 600–650°C): Dominated by the kaolinite dehydroxylation, leading to increased porosity but decreased average pore size; (3) intense change stage (550–600°C): Dominated by the quartz phase transitions, where the thermal stress generated by quartz phase transitions causes dramatic alterations in the internal structure of the sandstone. Furthermore, a correlation model between wave velocity and permeability of sandstone at high temperatures was established based on the interrelationship of these physical properties, providing a new method for real-time monitoring of permeability under high-temperature conditions.

Influence of Complex Lithology Distribution on Fracture Propagation Morphology in Coalbed Methane Reservoir

The mineral composition in coalbed methane (CBM) reservoirs significantly influences fracture morphology, making the description of reservoir heterogeneity challenging. This study develops a fracture propagation model for CBM reservoirs that incorporates the varying mineral properties within the reservoir’s lithology. Dynamic logging data are considered to characterize rock mechanical properties, which form the basis for in situ stress estimation. Using an adjusted critical circumferential stress calculation for coal rock, the model considers the impact of complex lithology on fracture propagation. A comprehensive fractal index is introduced to capture the influence of different minerals on fracture morphology and propagation randomness. Models representing clay, quartz, and pyrite with varied compositions were constructed to explore the effects of each mineral on fracture characteristics. In single-component models, clay-rich reservoirs exhibited the highest induced fracture density, with quartz and pyrite showing approximately 65% and 20% of the fracture density observed in clay, respectively. Fractures primarily propagated toward quartz-rich regions, while pyrite significantly inhibited fracture growth. In mixed-mineral models, increasing the quartz proportion by 40% resulted in a 20 m increase in fracture length and a 30% reduction in fracture density. Fractures predominantly propagated around pyrite boundaries, demonstrating pyrite’s resistance to fracture penetration. Clay and quartz promote fracture development, whereas pyrite hinders fracture formation. The fracture inversion model presented here effectively captures the influence of complex mineral distributions on fracture morphology, offering valuable insights for optimizing fracturing production strategies.

Experimental Investigation of CO2 Huff-and-Puff Enhanced Oil Recovery in Fractured Low-Permeability Reservoirs: Core-Scale to Pore-Scale

CO2 huff-n-puff is regarded as an effective method to improve the recovery of low permeability and tight oil reservoirs. To understand the impact of CO2 huff-n-puff on crude oil mobilization in tight reservoirs with different fracture scales, this study conducted CO2 huff-n-puff nuclear magnetic resonance (NMR) and microscopic visualization experiments, focusing on how varying fracture apertures and densities affect the efficiency of the CO2 huff-n-puff. The results show that in scenarios with a single fracture, larger fracture apertures significantly boost oil mobilization within the fracture and the surrounding matrix. For instance, increasing the aperture from 20 μm to 70 μm improved the recovery factor by 9.20%. In environments with multiple fractures, greater fracture density enhances reservoir connectivity, and increases the CO2 sweep area, and the complex fracture model shows a 4.26% increase in matrix utilization compared to the simple fracture model. Notably, the improvement in recovery due to multi-scale fractures is most significant during the first two huff-and-puff cycles, with diminishing returns in subsequent cycles. Overall, increasing both fracture size and density effectively enhances crude oil mobilization in tight reservoirs. These findings provide valuable insights into improving the recovery efficiency of CO2 huff-and-puff techniques in tight oil reservoirs.

A Study on the Influence of Natural Fractures in Tight Sandstone Reservoirs on Hydraulic Fracture Propagation Behavior and Post-Fracture Productivity

Tight sandstone gas reservoirs are rich in reserves and are an important part of unconventional oil and gas resources. However, natural fractures’ impact on hydraulic fracture propagation behavior and network formation mechanisms remain unclear. Exploring how to optimize fracturing parameters to maximize post-fracturing productivity requires further investigation. Therefore, this study focused on the characteristics of tight sandstone gas reservoirs and established a three-dimensional numerical simulation model for hydraulic fracture propagation and post-fracturing productivity using production history matching to validate the reliability of the model. Based on this model, this study investigated the influence mechanisms of natural fracture angles, density, and lengths on hydraulic fracture propagation behavior and network formation. The spatial distribution of hydraulic fracture widths in three dimensions is also explored. When natural fracture angles are lower, a greater number of natural fractures are activated, leading to more developed secondary hydraulic fractures and the formation of complex fracture networks. Hydraulic fractures tend to penetrate directly through high-angle natural fractures. Single-well cumulative gas production increases initially with increasing natural fracture angles, then decreases, but increases with higher natural fracture density and length. Optimal fracturing in areas with longer natural fractures, lower angles, and higher density distribution enhances single-well productivity effectively.

Péclet‐Number‐Dependent Longitudinal Dispersion in Discrete Fracture Networks

AbstractDispersion in fractured media impacts many environmental and geomechanical practices. It is mainly controlled by the structure of fracture networks and the Péclet number , but predicting it remains challenging. In this study, numerous three‐dimensional stochastic discrete fracture networks (DFNs) were generated, where the density, size, and orientation vary significantly. The aperture and conductivity are proportional to the size, following power‐laws. Through flow and transport simulation, we evaluated the longitudinal dispersion coefficients . We found that, as density increases, the tortuosity decreases and the first passage time distributions approximate bell‐shaped curves more closely, which suggests, but does not fully guarantee, that an asymptotic dispersion regime may emerge for denser DFNs, as solute particles traverse more fractures and the macroscopic inter‐fracture mixing is more homogeneous. We then determined the values for DFNs in which the time evolution of the variance of particle displacements becomes linear and hence asymptotic. The results show that both and fracture density affect , but the former has a much stronger influence than the latter. A new Péclet number was recalculated for all DFNs, where the characteristic length scale accounts for the influence of large fractures. Dimensionless values show a unique power‐law relationship with high values. Furthermore, when advection dominates, the dimensionless can be described by a universal finite‐size scaling function depending on fracture density and domain sizes. The findings of this study enhance the understanding of transport in fracture networks and imply the potential for predicting in a broad range of scenarios using statistics on fracture parameters obtainable at the field scale.

Impact of natural fractures on hydraulic fracture propagation in Denver-Julesburg Basin: Insights from a decade of research

The Denver-Julesburg (DJ) Basin is a key region for unconventional oil and gas extraction, particularly from the Niobrara and Codell formations. This study synthesizes findings from a decade of research conducted in three different geographic areas of the basin as part of the industry consortium Reservoir Characterization Project at Colorado School of Mines. The research explores how natural fractures affect hydraulic fracture propagation, leveraging geophysical data sets including 3D seismic imaging, image logs, microseismic monitoring, and crosswell distributed strain sensing. Key observations reveal significant variations in hydraulic fracture orientations and propagation speeds between the Niobrara and Codell formations, which are the main targets for horizontal drilling and stimulation. High natural fracture densities and orientations notably influence the propagation of hydraulic fractures in the Niobrara Formation, deviating them from the regional maximum horizontal stress (SHmax) directions, while hydraulic fractures in Codell consistently align with SHmax where lower natural fracture densities are observed. The study also highlights the critical role of stress anisotropy and zipper fracturing sequences in dictating hydraulic fracture behavior. Additionally, a marked negative correlation between natural fracture density and hydraulic fracture propagation speed underlines the fracture network complexity added by natural fractures. These findings advocate for a comprehensive natural fracture characterization and tailored fracturing strategies to optimize well placement and completions. The implications for DJ Basin development from this study are profound, suggesting that understanding local geomechanics and fracture networks can significantly enhance hydrocarbon recovery. Future work should focus on more precise assessments of hydraulic fracture interactions with natural fracture systems to refine operational strategies further.

Analysis on Correlation Model Between Fracture Network Complexity and Gas-Well Production: A Case in the Y214 Block of Changning, China

The fracture network of the Y214 block in the Changning area of China is complex, and there are significant differences in the productivity of different shale gas wells. However, traditional machine learning models have problems such as missing key parameters, poor fitting effects and low prediction accuracy, which make it difficult to effectively evaluate the impact of crack network complexity on productivity. Therefore, the Pearson correlation coefficient was used to analyze the correlation between evaluation parameters, such as mineral content, horizontal stress difference, natural fractures and gas production. Combined with the improved particle swarm optimization (IPSO) algorithm and support vector machine (SVM) algorithm, a fracture network index (FNI) model was proposed to effectively evaluate the complexity of fracture networks, and the model was verified by comparing it with the performance evaluation results from the other two traditional models. Finally, the correlation between the fracture network index and the actual average daily gas production of different fracturing sections was calculated and analyzed. The results showed that the density of natural fractures was the key factor in controlling gas production (the Pearson correlation coefficient was 0.39), and the correlation between other factors was weak. In the process of fitting the actual data, the coefficient of determination, R², of the IPSO-SVM-FNI model training set increased by 8% and 24% compared with the two traditional models, and the fitting effect was greatly improved. In the prediction process based on actual data, the R² of the IPSO-SVM-FNI model test set was improved by 22% and 20% compared with the two traditional models, and the prediction accuracy was also significantly improved. The fracture index was concentrated, and its main distribution range was in the range of [0.2, 0.8]. The fracturing section with a higher FNI showed higher average daily gas production, and there was a significant positive correlation between fracture network complexity and gas production. Indeed, the research results provide some ideas and references for the evaluation of fracturing effects in shale reservoirs.

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

The Cane Creek reservoir within the Paradox Basin in southeast Utah 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 analyze a previous hydraulic stimulation of the State 16-2 LN-CC 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: spatial correlations of various well logs to identify regions favorable for retaining hydrocarbons within natural fractures, analysis of pressure-time data from the hydraulic fracturing stages during well stimulation to assess the complexity of the fracture networks, and 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 LN-CC stimulation and yield specific recommendations. The most important recommendation is to stimulate regions with geomechanically stable fractures due to their ability to retain hydrocarbons. Restimulation, if needed, may be more effective if completed after significant depletion due to poroelastic stress changes. Although the direction of maximum horizontal stress is a critical factor, it might be less crucial if restimulation is conducted after considerable reservoir depletion.