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Aquitard consolidation in the Chalco Plain is the most recent of a series of major land subsidence problems near Mexico City caused by leaky‐aquifer pumping and involving a complex distribution of basalt flows within a lacustrine sequence. This study first conducted a ground magnetic survey combined with lithologic logs to map the extension of basalts. Then it assessed the evolution of ground surface elevations and updated hydraulic heads in the aquifer and aquitard in order to verify the accuracy of previous simulations and develop new predictions on land subsidence employing a one‐dimensional, nonlinear, groundwater flow‐consolidation model. Results show the presence of shallow basalts that extend from Sierra Santa Catarina into the Chalco Plain, causing a differential consolidation that controls both the distribution of large‐scale fractures in the aquitard and the shape of a new lake. Cumulative land subsidence in the center of the Chalco Plain reached 13 m in 2006, thus closely matching previous numerical estimations. Since 1985, the ground surface decline has continued at a rate of ∼0.40 m/yr, while the potentiometric surface decline in the aquifer proceeds at an average rate of approximately 1.5 m/yr, indicating that the flow system has not yet reached steady‐state conditions. Numerical predictions show that under current pumping rates, where the aquitard is 300 m, total land subsidence will reach approximately 19 m by the year 2020; while where the aquitard is 140 m thick, total land subsidence will reach approximately 12 m, and increase the risk of flooding and aquitard fracturing for nearby urban centers.

The coalbed methane (CBM) productivity is directly determined by the fracture permeability during hydraulic fracturing, which is regulated by the distribution of proppants. The proppant may be unevenly distributed in the fracture because of variables like the architecture of the fracture and the characteristics of the sand‐carrying fluid. This study used two types of random functions to produce different ununiform distributions of proppant clusters in large‐scale fractures, with the aim of investigating the effect of these distributions on the overall permeability of the fracture. A model of fluid‐structure coupling is proposed. The closure of large‐scale fractures under in‐situ stress is analyzed using solid mechanics and the penalty function; the CBM flowing in proppant clusters and the high‐speed channel between them is simulated using Darcy's law and the Navier–Stokes equation, respectively; and the overall permeability of fractures is computed using the fluid pressure drop throughout the fracture and the fluid flowing velocity in the fracture's outlet. Since most CBM flows along high‐speed channels between the proppant clusters, the simulated findings show that the overall permeability of fractures with an uneven distribution of proppant clusters is significantly higher than that of the proppant cluster itself. As CBM becomes more discretely distributed, the proportion of CBM flowing within the proppant cluster continuously drops. As the permeability of the proppant cluster increases, the volume ratio of proppant clusters decreases, and the distribution of proppant clusters becomes more discrete, the overall permeability of the fracture continuously increases. Overall permeability of fractures with uniform random distribution of proppant.

Lost circulation critically jeopardizes drilling safety and efficiency, and remains an unresolved challenge in oil and gas engineering. In this paper, by utilizing the self-developed dynamic plugging apparatus and synthetic cores containing large-scale fractures, experimental research on the circulation plugging of different materials was conducted. Based on the D90 rule and fracture mechanical aperture model, we analyze the location of plugging layer under dynamic plugging mechanism. By setting different parameters of fracture width and injection pressure, the laws of cyclic plugging time, pressure bearing capacity and plugging layers formation were investigated. The results show that the comprehensive analysis of particle size and fracture aperture provides an accurate judgment of the entrance-plugging phenomenon. The bridging of solid materials in the leakage channel is a gradual process, and the formation of a stable plug requires 2–3 plug-leakage cycles. The first and second cyclic plugging time was positively correlated with the fracture width. Different scales of fractures were successfully plugged with the bearing pressure greater than 6 MPa, but there were significant differences in the composition of the plugging layer. The experimental results can effectively prove that the utilized plugging agent is effective and provides an effective reference for dynamic plugging operation.

The variation of fractal dimension and entropy during a damage evolution process, especially approaching critical failure, has been recently investigated. A sudden drop of fractal dimension has been proposed as a quantitative indicator of damage localization or a likely precursor of an impending catastrophic failure. In this contribution, electromagnetic emissions recorded prior to significant earthquake are analysed to investigate whether they also present such sudden fractal dimension and entropy drops as the main catastrophic event is approaching. The pre-earthquake electromagnetic time series analysis results reveal a good agreement to the theoretically expected ones indicating that the critical fracture is approaching.

hailaer oilfield belongs to low permeability fault-block oilfield, some blocks effectively injection Wells after fracturing is still hard, lead to low formation pressure, the late refracturing effect is poor, single and average increased under 400 t oil and to explore effective fracturing technology in the low permeability elastic exploration area, hailaer oilfield since 2011, in fissured budate reservoir, according to the characteristics of the reservoir Large-scale clear water fracture network fracturing tests have been carried out, and better stimulation effect has been achieved. The tests have guiding significance for the effective development of low efficiency and difficult to recover reservoirs in Hailaer oilfield.

Fractures in reservoirs significantly affect reservoir flow properties in subsequent years, which means that fracture characteristics such as preferred orientation, crack density or fracture compliance, what filling is in the fractures and so on are of great importance for reservoir development. When fractures are vertical, aligned and their dimensions are small relative to the seismic wavelength, the medium can be considered to be an equivalent horizontal transverse isotropic (HTI) medium. However, geophysical data acquired over naturally fractured reservoirs often reveal the presence of multiple fracture sets. We investigate a case where there are two vertical sets of fractures having differing length scales. One fracture set has length scale that is much smaller than the seismic wavelength but the other has length scale that is similar to the seismic wavelength. We use synthetic data to investigate the ability to infer the properties of the small-scale fractures in the presence of the large-scale fracture set. We invert for the Thomsen-type anisotropic coefficients of the small-scale fracture set by using the difference of the P wave amplitudes at two azimuths, which makes the inversion convex. Then we investigate the influence of the presence of the large-scale fractures on our ability to infer the properties of the small-scale fracture set. Surprisingly, we find that we can reliably infer the fracture density of the small-scale fractures even in the presence of large-scale fractures having significant compliance values. Although the inversion results for Thomsen-type anisotropic coefficients of small-scale fractures for one model are not good enough to figure out whether it is gas-filled or fluid-filled, we can find a big change of Thomsen-type anisotropic coefficient between the models in which small-scale fractures are filled with gas and fluid.

Background Vertebral augmentation, such as vertebroplasty (VP) or kyphoplasty (KP), has been utilized for decades to treat OVCFs; however, the precise impact of this procedure on reducing mortality risk remains a topic of controversy. This study aimed to explore the potential protective effects of vertebral augmentation on mortality in patients with osteoporotic vertebral compression fractures (OVCFs) using a large-scale meta-analysis. Materials and methods Cochrane Library, Embase, MEDLINE, PubMed and Web of Science databases were employed for literature exploration until May 2023. The hazard ratios (HRs) and 95% confidence intervals (CIs) were utilized as a summary statistic via random-effect models. Statistical analysis was executed using Review Manager 5.3 software. Results After rigorous screening, a total of five studies with substantial sample sizes were included in the quantitative meta-analysis. The total number of participants included in the study was an 2,421,178, comprising of 42,934 cases of vertebral augmentation and 1,991,244 instances of non-operative management. The surgical intervention was found to be significantly associated with an 18% reduction in the risk of mortality (HR 0.82; 95% CI 0.78, 0.85). Subgroup analysis revealed a remarkable 71% reduction in mortality risk following surgical intervention during short-term follow-up (HR 0.29; 95% CI 0.26, 0.32). Furthermore, KP exhibited a superior and more credible decrease in the risk of mortality when compared to VP treatment. Conclusions Based on a comprehensive analysis of large samples, vertebral augmentation has been shown to significantly reduce the mortality risk associated with OVCFs, particularly in the early stages following fractures. Furthermore, it has been demonstrated that KP is more reliable and effective than VP in terms of mitigating mortality risk.

Using the natural limestone samples taken from the field with dimension of 500 mm×500 mm×1 000 mm, the D-D (dilatancy-diffusion) seismogeny pattern was modeled under the condition of water injection, which observes the time-space evolutionary features about the relative physics fields of the loaded samples from deformation, formation of microcracks to the occurrence of main rupture. The results of observed apparent resistivity show: 1 The process of the deformation from microcrack to main rupture on the loaded rock sample could be characterized by the precursory spatial-temporal changes in the observation of apparent resistivity; 2 The precursory temporal changes of observation in apparent resistivity could be divided into several stages, and its spatial distribution shows the difference in different parts of the rock sample; 3 Before the main rupture of the rock sample the obvious \"tendency anomaly\" and \"short-term anomaly\" were observed, and some of them could be likely considered as the \"impending earthquake\" anomaly precursor of apparent resistivity. The changes and distribution features of apparent resistivity show that they are intrinsically related to the dilatancy phenomenon of the loaded rock sample. Finally, this paper discusses the mechanism of resistivity change of loaded rock sample theoretically.[PUBLICATION ABSTRACT]

Hydraulic fracture propagation under natural fracture distributions has always been a hot topic in unconventional reservoir stimulation. In this work, the hydromechanical behavior controlled by rock fabric is understood and quantified via physical and numerical simulations. A unique large-scale (762 mm × 762 mm × 914 mm) hydraulic fracturing simulation experimental technology considering quantitative simulation of the cementation performance of natural fractures is established. Combined with the laboratory results, a planar, heterogeneous, multiscale hydraulic fracturing numerical model based on the cohesive zone method is developed and verified. The experimental and numerical results reveal three simple modes between hydraulic fracture and natural fracture, namely, natural fracture opening, shearing and crossing. In addition, some mixed modes of complex fracture exist. Compared with engineering factors, the interaction between natural fractures and hydraulic fractures is more obviously controlled by geological factors. A greater horizontal stress difference, angle between the maximum horizontal stress direction and natural fracture, tensile strength of natural fractures and pumping parameters are conducive to crossing natural fractures. On the basis of the simulation results, three field-scale diagrams of the interaction between natural fractures and hydraulic fractures are systematically established. The interaction results can be visualized in reference to most geological and engineering conditions. Considering the greater horizontal stress difference and natural underdevelopment, the single model of fracture propagation along the maximum direction is dominant in most tight or shale oil basins in China. The physical and numerical simulation technologies in this paper will help to optimize the volume stimulation design of unconventional reservoirs.HighlightsA unique large-scale hydraulic fracturing simulation experimental technology considering quantitative simulation of the cementation performance of natural fractures is establishedThree field-scale diagrams of the interaction between natural fracture and hydraulic fracture are established systematicallyRevealing the interaction mechanism between hydraulic fracture and natural fracture

Background The Affordable Care Act of 2010 advanced the economic model of bundled payments for total joint arthroplasty (TJA), in which hospitals will be financially responsible for readmissions, typically at 90 days after surgery. However, little is known about the financial burden of readmissions and what patient, clinical, and hospital factors drive readmission costs. Questions/purposes (1) What is the incidence, payer mix, and demographics of THA and TKA readmissions in the United States? (2) What patient, clinical, and hospital factors are associated with the cost of 30- and 90-day readmissions after primary THA and TKA? (3) Are there any differences in the economic burden of THA and TKA readmissions between payers? (4) What types of THA and TKA readmissions are most costly to the US hospital system? Methods The recently developed Nationwide Readmissions Database from the Healthcare Cost and Utilization Project (2006 hospitals from 21 states) was used to identify 719,394 primary TJAs and 62,493 90-day readmissions in the first 9 months of 2013 based on International Classification of Diseases, 9th Revision, Clinical Modification codes. We classified the reasons for readmissions as either procedure- or medical-related. Cost-to-charge ratios supplied with the Nationwide Readmissions Database were used to compute the individual per-patient cost of 90-day readmissions as a continuous variable in separate general linear models for THA and TKA. Payer, patient, clinical, and hospital factors were treated as covariates. We estimated the national burden of readmissions by payer and by the reason for readmission. Results The national rates of 30- and 90-day readmissions after THA were 4% (95% confidence interval [CI], 4.2%–4.5%) and 8% (95% CI, 7.5%–8.1%), respectively. The national rates of 30- and 90-day readmissions after primary TKA were 4% (95% CI, 3.8%–4.0%) and 7% (95% CI, 6.8%–7.2%), respectively. The five most important variables responsible for the cost of 90-day THA readmissions (in rank order, based on the Type III F-statistic, p < 0.001) were length of stay (LOS), all patient-refined diagnosis-related group (APR DRG) severity, type of readmission (that is, medical- versus procedure-related), hospital ownership, and age. Likewise, the five most important variables responsible for the cost of 90-day TKA readmissions were LOS, APR DRG severity, gender, hospital procedure volume, and hospital ownership. After adjusting for covariates, mean 90-day readmission costs reimbursed by private insurance were, on average, USD 1324 and USD 1372 greater than Medicare (p < 0.001) for THA and TKA, respectively. In the 90 days after TJA, two-thirds of the total annual readmission costs were covered by Medicare. In 90 days after THA, more readmissions were still associated with procedure-related complications, including infections, dislocations, and periprosthetic fractures, which in aggregate account for 59% (95% CI, 59.1%–59.6%) of the total readmission costs to the US healthcare system. For TKA, 49% of the total readmission cost (95% CI, 48.8%–49.6%) in 90 days for the United States was associated with procedure issues, most notably including infections. Conclusions Hospital readmissions up to 90 days after TJA represent a massive economic burden on the US healthcare system. Approximately half of the total annual economic burden for readmissions in the United States is medical and unrelated to the joint replacement procedure and half is related to procedural complications. Clinical Relevance This national study underscores LOS during readmission as a primary cost driver, suggesting that hospitals and doctors further optimize, to the extent possible, the clinical pathways for the hospitalization of readmitted patients. Because patients readmitted as a result of infection, dislocation, and periprosthetic fractures are the most costly types of readmissions, efforts to reduce the LOS for these types of readmissions will have the greatest impact on their economic burden. Additional clinical research is needed to determine the extent to which, if any, the LOS during readmissions can be reduced without sacrificing quality or access of care.