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Complex fracture technology is key to the successful development of unconventional oil and gas reservoirs, such as shale. Most current studies focus on how to improve the complexity of the fracture network. It is still unclear whether proppant can enter the branch fractures at all levels after the formation of complex fractures. The effects of construction displacement, proppant particle size, proppant density, fracturing fluid viscosity, sand ratio, and other factors on proppant migration in single fractures and complex fractures were studied using an experimental device independently developed by the laboratory. The results show that the lowest point height of the sandbank and the equilibrium height of the sandbank are directly proportional to the particle concentration and density, respectively, and inversely proportional to the displacement and fracturing fluid viscosity. The equilibrium time of the sandbank is inversely proportional to the displacement, particle concentration, and density, respectively, and proportional to the viscosity of the fracturing fluid. Under the same experimental conditions, the larger the branch angle, the smaller the height of the main/secondary fracture sandbank. In the design of the fracturing process, fracturing fluid with varying viscosities and proppant with different densities should be selected according to the formation conditions and fracturing targets. In the face of long fracture lengths, the combination of low-viscosity fracturing fluid with an appropriate viscosity and low-density proppant can meet the goal of placing proppant over long distances and effectively supporting fractures over extended lengths. Subsequently, high-density proppant or reduced construction displacement are adopted to usefully support fractures in the near-wellbore area. The results of this paper can provide theoretical support for proppant selection and fracturing program design. [ABSTRACT FROM AUTHOR]

Aims: Ankle fracture is one of the most common musculoskeletal injuries sustained in the UK. Many patients experience pain and physical impairment, with the consequences of the fracture and its management lasting for several months or even years. The broad aim of ankle fracture treatment is to maintain the alignment of the joint while the fracture heals, and to reduce the risks of problems, such as stiffness. More severe injuries to the ankle are routinely treated surgically. However, even with advances in surgery, there remains a risk of complications; for patients experiencing these, the associated loss of function and quality of life (Qol) is considerable. Non-surgical treatment is an alternative to surgery and involves applying a cast carefully shaped to the patient’s ankle to correct and maintain alignment of the joint with the key benefit being a reduction in the frequency of common complications of surgery. The main potential risk of non-surgical treatment is a loss of alignment with a consequent reduction in ankle function. This study aims to determine whether ankle function, four months after treatment, in patients with unstable ankle fractures treated with close contact casting is not worse than in those treated with surgical intervention, which is the current standard of care. Methods: This trial is a pragmatic, multicentre, randomized non-inferiority clinical trial with an embedded pilot, and with 12 months clinical follow-up and parallel economic analysis. A surveillance study using routinely collected data will be performed annually to five years post-treatment. Adult patients, aged 60 years and younger, with unstable ankle fractures will be identified in daily trauma meetings and fracture clinics and approached for recruitment prior to their treatment. Treatments will be performed in trauma units across the UK by a wide range of surgeons. Details of the surgical treatment, including how the operation is done, implant choice, and the recovery programme afterwards, will be at the discretion of the treating surgeon. The non-surgical treatment will be close-contact casting performed under anaesthetic, a technique which has gained in popularity since the publication of the Ankle Injury Management (AIM) trial. In all, 890 participants (445 per group) will be randomly allocated to surgical or non-surgical treatment. Data regarding ankle function, QoL, complications, and healthcare-related costs will be collected at eight weeks, four and 12 months, and then annually for five years following treatment. The primary outcome measure is patient-reported ankle function at four months from treatment. Anticipated impact: The 12-month results will be presented and published internationally. This is anticipated to be the only pragmatic trial reporting outcomes comparing surgical with non-surgical treatment in unstable ankle fractures in younger adults (aged 60 years and younger), and, as such, will inform the National Institute for Health and Care Excellence (NICE) ‘non-complex fracture’ recommendations at their scheduled update in 2024. A report of long-term outcomes at five years will be produced by January 2027. Cite this article: Bone Jt Open 2024;5(3):184–201.

Introduction: The therapeutic management of calcaneal fractures is currently a major source of controversy in the literature. There is no consensus on the need to treat these injuries conservatively or surgically, nor on the criteria for deciding one option or the other. Although the gold standard has classically been the open approach and osteosynthesis, there are currently minimally invasive techniques that also report good results. Our objective is to present our results and experience with the MBA® Orthofix external fixator in a series of cases of calcaneal fractures. Methods: We performed a retrospective observational study in our center, between the years 2019 and 2021, of Sanders types II–IV calcaneal fractures operated with MBA® Orthofix external fixator. We recorded a total of 38 patients, 42 fractures. We registered demographic information, intraoperative, postoperative, radiological and functional parameters, using the American Orthopedic Foot and Ankle Society (AOFAS), Manchester-Oxford Foot Questionnaire (MOXFQ), EQ-5D and VAS scales. Results: A total of 26 men and 12 women were included, and the median age was 38 years. Mean follow-up was 24,4 months (6, 8–40, 1). The average time to surgery was 7 days and partial loading was started at 2.5 weeks after external fixation, which was removed at 9.2 weeks. The average Böhler angle correction was 7, 4°, Gissane − 12,2°, length 2 mm and calcaneal width was reduced by 5 mm. We recorded two superficial infections, one peroneal entrapment and three subtalar arthrodesis due to post-traumatic osteoarthritis. The AOFAS obtained was 79.1 + / − 15.7 points, MOXFQ 20.1 + / − 16.1 points, EQ-5D 0.84 + / − 0.2 and VAS 3.3 + / − 1.9. Conclusion: The external fixator is an excellent surgical alternative for complex articular fractures of the calcaneus, obtaining clinical and radiological results comparable to other osteosynthesis techniques and significantly reducing soft tissue complications. [ABSTRACT FROM AUTHOR]

The proppant placement rule in complex fractures is relatively complex. At present, most of the research are based on numerical simulation methods, which are time-consuming and laborious. The numerical simulation method was used to study the influence of injection rate, fluid viscosity, sand ratio, particle size and density on the placement effect. And on this basis, the neural network prediction model of effective proppant support area in fractures was established by using neural network and experimental data. The results show that there are different reasonable ranges in these factors, and exceeding this range can lead to poor laying effect. The variation laws in different levels of cracks are different, and the proppant laying of the main and secondary joints are mutually affected. After the height of the sand embankment of the main joint before branching exceeds a certain height, the higher the sand embankment height, the smaller the sand embankment area of the secondary joint is,and the maximum sand embankment area of the main and secondary joints appear at different times. There is 3. 42% ~ 6. 46% error between the numerical calculation result and the model prediction result which is obtained from the prediction model of effective support area in cracks based on back propagation (BP) neural network. The area of sand dike formed after proppant migration in the fractures is predicted accurately and quickly. The research is of great significance to the fracturing development of unconventional resources. [ABSTRACT FROM AUTHOR]

Faced with difficulties stemming from the complex interactions between tight gas sand bodies and fractures, when describing and identifying reservoirs, a composite reservoir model was established. By setting the supply boundary to characterize the superposition characteristics of sand bodies, a mathematical model of unstable seepage in fractured vertical wells in tight sandstone gas reservoirs was developed, considering factors such as stress sensitivity, fracture density and fracture symmetry. The seepage law and pressure response characteristics of gas wells in tight sandstone discontinuous reservoirs with stress sensitivity, semi-permeable supply boundary and complex fracture topology were determined, and the reliability of the model was verified. The research results more accurately display the pressure characteristic of a vertical well in the superimposed sand body with complex fractures and provide a more comprehensive model for tight gas production dynamic analysis and well test data analysis, which can more accurately guide the dynamic inversion of reservoir and fracture parameters. [ABSTRACT FROM AUTHOR]

Abstract As an unconventional oil and gas resource, coalbed methane has become a key area of unconventional oil and gas exploration worldwide, and hydraulic fracturing is the critical technology for the efficient stimulation of coalbed methane. However, due to the strong heterogeneity of deep coal seam reservoirs and the development of natural cleat fractures, the fracture propagation path is quite complex and difficult to capture. In this study, we propose a hydraulic fracture propagation simulation method using the ABAQUS Software for natural cleat fracture networks and a fluid–solid fully coupled two‐dimensional finite element model with the global embedded cohesive zone model (CZM). CZM is established to simulate the propagation of hydraulic fractures in the heterogeneous combination of coal rock and mudstone. The accuracy of this model is verified by using Blanton's experiment criterion. Finally, the model is used to simulate the influence of cleat angle, cleat density, length ratio of coal rock and mudstone combination, and construction displacement on the propagation behavior of hydraulic fractures. This study aims to deepen the understanding of the mechanism of hydraulic fracture propagation in deep coal seams and provides guidance for deep coal seam fracturing and hydraulic fracturing design.

Background Proximal humeral fractures with increasing incidence are common over the past decades. Among them, the complicated and displaced ones, especially combined with the proximal third humeral shaft fractures, need to be treated surgically. Humeral intramedullary nail and locking plate are the most frequently used options. However, few studies address the application of nail‐plate combination for management. Case presentation A 49‐year‐old man struck by a car was referred to our emergency trauma center. The X‐ray and three‐dimensional computed tomography (CT) showed a complex proximal humeral fracture with proximal third shaft fracture. No evidence of other associated injuries and neurovascular symptom of the injured left upper limb was shown by physical examination. Nail‐plate fixation was performed to restore the anatomic integrity of proximal humerus. The injured arm was maintained in a broad arm sling for 14 days after surgery. The active as well as positive movements under the instruction were encouraged as long as the pain could be tolerated from postoperative day 2. One year after the surgery, the fracture was healed, and the patient regained normal shoulder motion. The good clinical outcomes were obtained by application of nail‐plate fixation to treat complex proximal third humeral shaft fractures. Thus, this surgical intervention could be performed as an alternative.

Complex fracture technology is key to the successful development of unconventional oil and gas reservoirs, such as shale. Most current studies focus on how to improve the complexity of the fracture network. It is still unclear whether proppant can enter the branch fractures at all levels after the formation of complex fractures. The effects of construction displacement, proppant particle size, proppant density, fracturing fluid viscosity, sand ratio, and other factors on proppant migration in single fractures and complex fractures were studied using an experimental device independently developed by the laboratory. The results show that the lowest point height of the sandbank and the equilibrium height of the sandbank are directly proportional to the particle concentration and density, respectively, and inversely proportional to the displacement and fracturing fluid viscosity. The equilibrium time of the sandbank is inversely proportional to the displacement, particle concentration, and density, respectively, and proportional to the viscosity of the fracturing fluid. Under the same experimental conditions, the larger the branch angle, the smaller the height of the main/secondary fracture sandbank. In the design of the fracturing process, fracturing fluid with varying viscosities and proppant with different densities should be selected according to the formation conditions and fracturing targets. In the face of long fracture lengths, the combination of low-viscosity fracturing fluid with an appropriate viscosity and low-density proppant can meet the goal of placing proppant over long distances and effectively supporting fractures over extended lengths. Subsequently, high-density proppant or reduced construction displacement are adopted to usefully support fractures in the near-wellbore area. The results of this paper can provide theoretical support for proppant selection and fracturing program design.

As an unconventional oil and gas resource, coalbed methane has become a key area of unconventional oil and gas exploration worldwide, and hydraulic fracturing is the critical technology for the efficient stimulation of coalbed methane. However, due to the strong heterogeneity of deep coal seam reservoirs and the development of natural cleat fractures, the fracture propagation path is quite complex and difficult to capture. In this study, we propose a hydraulic fracture propagation simulation method using the ABAQUS Software for natural cleat fracture networks and a fluid–solid fully coupled two‐dimensional finite element model with the global embedded cohesive zone model (CZM). CZM is established to simulate the propagation of hydraulic fractures in the heterogeneous combination of coal rock and mudstone. The accuracy of this model is verified by using Blanton's experiment criterion. Finally, the model is used to simulate the influence of cleat angle, cleat density, length ratio of coal rock and mudstone combination, and construction displacement on the propagation behavior of hydraulic fractures. This study aims to deepen the understanding of the mechanism of hydraulic fracture propagation in deep coal seams and provides guidance for deep coal seam fracturing and hydraulic fracturing design. [ABSTRACT FROM AUTHOR]

The placement of proppant within fractures is critical to the effectiveness of hydraulic fracturing. To elucidate the migration and placement patterns of proppant within multi-branched fractures during hydraulic fracturing, we conducted simulation experiments under both single-fracture and multi-branched-fracture conditions, varying injection rates and proppant sizes. The results of the research indicate that increasing the injection rate effectively increases the magnitude of vortex formation at the leading edge of sandbars and the drag forces acting on the proppant particles, resulting in increased particle migration distances. However, effective proppant packing near the wellbore entrance is not achieved at higher injection rates, leaving the fractures susceptible to closure under in situ stress, thereby reducing overall fracture conductivity. In addition, increasing the proppant size results in higher settling velocities and weakens the vortex's ability to entrain the proppant particles. This results in shorter proppant placement distances, and the proppant cannot effectively reach the distant branched fractures. In addition, the diversionary effect of the branched fractures gradually reduces the flow rate in the distant branches, resulting in poorer proppant placement efficiency. Based on these findings, we recommend an approach that initially increases injection rates while reducing proppant size to ensure proppant placement in distant wellbore fractures and branched fracture networks. Subsequently, larger proppants can be used to effectively fill fractures close to the wellbore. [ABSTRACT FROM AUTHOR]

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By tapping the potential of early flowback data resources, a post-fracturing evaluation method for shale oil horizontal wells based on flowback performance analysis was proposed. Considering the complex propped patterns of shale fractures, the effective fractures were divided into proppant-propped main fracture and liquid-propped secondary fracture. Based on the flowing-materialbalance equation, a mathematical model and iterative solution approach were established, and their applicability was verified by numerical simulation. Taking four multi-fractured horizontal wells in Jimusar shale reservoir as an example, the analysis flow of the new method was introduced in detail to reverse the effective fracture volume, fracture complexity and fracturing fluid efficiency. The calculation show that the fracture network formed after fracturing is mainly the liquid-propped secondary fractures, and only about 34% of the fracturing fluid contributed to the fracture conductivity during production. The fracturing fluid efficiency and flowback efficiency decreases by increasing fluid intensity. The results show that this method can fully utilize the flowback data to estimate effective fracture volume, fracture complexity and fracturing fluid efficiency. It is practical in post-fracturing evaluation. [ABSTRACT FROM AUTHOR]

Background: Proximal humeral fractures with increasing incidence are common over the past decades. Among them, the complicated and displaced ones, especially combined with the proximal third humeral shaft fractures, need to be treated surgically. Humeral intramedullary nail and locking plate are the most frequently used options. However, few studies address the application of nail‐plate combination for management. Case presentation: A 49‐year‐old man struck by a car was referred to our emergency trauma center. The X‐ray and three‐dimensional computed tomography (CT) showed a complex proximal humeral fracture with proximal third shaft fracture. No evidence of other associated injuries and neurovascular symptom of the injured left upper limb was shown by physical examination. Nail‐plate fixation was performed to restore the anatomic integrity of proximal humerus. The injured arm was maintained in a broad arm sling for 14 days after surgery. The active as well as positive movements under the instruction were encouraged as long as the pain could be tolerated from postoperative day 2. One year after the surgery, the fracture was healed, and the patient regained normal shoulder motion. The good clinical outcomes were obtained by application of nail‐plate fixation to treat complex proximal third humeral shaft fractures. Thus, this surgical intervention could be performed as an alternative. [ABSTRACT FROM AUTHOR]

The Xujiahe Formation in western Sichuan has complex geological characteristics, fractures and fractures, and is prone to collapse in drilling. In this paper, the in-situ stress field around the wellbore, pore pressure, internal pressure in the wellbore and additional stress field generated by fluid flow are taken into account, and combined with the mechanical strength of rock in the target block, the in-situ stress parameters are calculated, the collapse pressure model of fractured formation is established, and the formation pressure profile of the well area is obtained, so as to predict the safe drilling fluid density window. The results show that the accuracy of the in-situ stress model is high, and the maximum error is 1.3%, which meets the engineering requirements. In the target block, the collapse pressure of Section 5 of Xinsheng 101 well and Section 5 – Section 3 of Xin601 well is high, reaching 1.8 g/cm3, and the safe drilling fluid density is narrow. Therefore, the drilling fluid density should be carefully designed to ensure the stability of borehole wall and prevent the occurrence of borehole wall collapse caused by too low drilling fluid density. [ABSTRACT FROM AUTHOR]

Platform well fracturing is essential for the efficient development of unconventional oil and gas (UOG), and it has been widely applied in oilfields. Field practices have revealed that various fracturing methods result in different stimulation performances, but the mechanisms responsible for these differences are not completely understood. To explore the characteristics of the inter-well stress interference of various platform well fracturing methods, a numerical model was established for the systematic assessment of the stress field of simultaneous fracturing, zipper fracturing (ZF), modified zipper fracturing, and synergic fracturing (SF). Based on these analyses, balanced stress fracturing (BSF) has been proposed to significantly reduce the horizontal stress difference. This study indicates that the fracturing methods significantly impact the evolution of induced stress, and that ZF and SF can achieve a balanced stress field and the utilization of an inter-well reservoir through a reasonable fracture distribution mode and fracturing operation. Combined with the interlaced fracture distribution mode, interactive fracturing, and overall front parallel fracturing, BSF can improve the fracture network complexity (FNC) and reduce the risk of casing deformation. Moreover, BSF helps achieve higher production and a more uniform stress field in platform well fracturing. This study presents an effective measure to increase FNC and reduce the occurrence of casing deformation during UOG development.

Complex fracture network is easy to form after hydraulic fracturing in coalbed methane reservoir. In order to study the influencing factors of complex fracture conductivity, an improved proppant filling fracture conductivity tester was used to evaluate the effects of proppant particle size, sand concentration, coal elastic modulus, coal powder content and fracturing fluid type on complex fracture conductivity in coalbed methane reservoir. The results show that: under the same sand concentration, the conductivity of E-type fracture is significantly greater than that of T-type fracture and single fracture, that is, the more complex the fracture morphology is, the greater the conductivity is; the conductivity of ceramsite as proppant is significantly greater than that of coated sand and quartz sand; the higher the sand concentration is, the greater the elastic modulus of coal and rock is, the greater the conductivity of fracture is; coal powder and fracturing fluid have great influence on fracture conductivity. The higher the content of coal powder is, the higher the damage rate to fracture conductivity is. Guar gum fracturing fluid has the greatest damage to fracture conductivity, followed by clean fracturing fluid and active hydraulic fracturing fluid. In addition, the more complex the fracture morphology is, the more serious the damage degree of coal powder and fracturing fluid to fracture conductivity is.

Massive hydraulic fracturing (MHF) is currently the most effective technology used to create fracture networks with sufficient conductivity and maximize the stimulated reservoir volume (SRV) in tight oil and gas reservoirs. The newly initiated fracture networks during MHF usually exhibit complex fracture morphology and contain intersected fractures and fracture branches. The conductivity of these fractures plays a pivotal role in determining long-term productivity. Due to the complex geometry, it is difficult to accurately evaluate intersected fracture conductivity through traditional conductivity measurement methods and devices which are designed for a single primary fracture. Unlike previous studies where fracture conductivity was measured using two rock slabs under single-direction (vertical) loading, we establish a novel conductivity measurement apparatus that can mimic different fracture intersection scenarios under both vertical and transverse loading to facilitate the evaluation of intersected fracture conductivity. Based on this apparatus, a standard conductivity measurement framework for intersected fractures under biaxial compaction conditions is also proposed, and stable and reliable conductivity testing data are obtained. Sensitivity analyses are performed to find out the controlling factors of intersected fracture conductivity and the corresponding conductivity evolution law. Results indicate that the overall intersected fracture conductivity of intersected fractures can be divided into three stages, with closure pressure increasing, videlicet, the conductivity rapid reduction stage at low closure pressure, the conductivity slow reduction stage, and the conductivity stabilization stage. Higher proppant concentration results in higher conductivity. However, the conductivity differences among cases with different proppant concentration are relatively small at high closure pressure (conductivity stabilization stage). The more complex the fracture intersecting pattern is, the higher the conductivity would be. The experimental results can provide guidance for the design of proppant placement procedure for intersected fractures. [ABSTRACT FROM AUTHOR]

• Lack of rehabilitation is a huge issue for people with complex fractures following traumatic injury. • This scoping review found significant heterogeneity in the literature with multiple different intervention components. • Reporting of interventions is poor despite validated tools such as the TIDieR framework being available to researchers. • Development of future interventions needs to involve key stakeholders, principally the patient voice. Complex fractures are severe injuries that cause considerable disability, particularly in the working population. Effective rehabilitation is essential to achieve good outcomes, however, it is unclear what the best rehabilitation strategy is for adults with complex fractures, after their discharge from hospital. The aim of this scoping review was to identify and map the breadth of evidence available on this topic. A systematic search was completed on 24th July 2023 using a combination of subject and specialist databases. In addition, a secondary search assessed unpublished literature from trial registries. A citation search was completed on the selected studies. The template for intervention description and replication (TIDieR) checklist was used to extract consistent data on the interventions reported in the studies. The Joanna Briggs Institute methodology for scoping reviews was followed. 19,253 studies were identified from the search strategy of which 25 studies met the eligibility criteria. Most interventions were exercise-based and delivered by physiotherapists. Some studies compared manual therapy treatments to other forms of physiotherapy or a placebo, whilst others investigated psychosocial interventions, such as cognitive behavioural therapy, in comparison to usual care. Two studies took a multidisciplinary team approach, incorporating components such as exercise, functional activities and self-management strategies. The studies included were heterogenous in terms of population (fracture type, location and complexity), intervention content and therapeutic aims. However, commonalities were found with most interventions or comparators including range of movement, strengthening and task specific exercises; functional tasks; gait and balance training; and advice on return to activities as components. Value was attributed to components such as, a coordinated team approach, person-centred rehabilitation, supervised exercise and psychosocial support. There is a broad and varied approach to the rehabilitation of complex fractures. The studies differed in population and approach, with a wide range of injuries, interventions and modes of delivery reported. Fidelity was poorly described, with only a third of studies reporting adherence or acceptability. There was inconclusive evidence to inform clinical practice and further research is advised. Qualitative, expert consensus, and coproduction approaches are recommended methods to develop complex interventions and best practice guidance. [ABSTRACT FROM AUTHOR]

• Complex hydraulic fractures still can be created under high stress level. • The growth of the stress level tends to improve fracture complexity in same stress difference. • The alteration in vertical or horizontal maximum stress can significantly affect the morphology of hydraulic fractures. • The intersection with multiple closely spaced joints form stepped morphology features. Compared with shallow reservoirs of shale gas, the high stress and plasticity of shale reservoirs under deep conditions significantly impact the propagation of hydraulic fractures. The study investigates the characteristics of hydraulic fracture propagation in deep shale reservoirs by conducting true triaxial fracturing tests at different stress levels and combinations under circumstances close to the original in-situ stress of the target reservoir. Specifically, it includes comparative experiments under high and low-stress levels, variable stress combinations with equal stress differences, and experiments on the influence of maximum and minimum horizontal in-situ stress, respectively. Through a series of experimental studies, it has been shown that the fracture roughness is relatively low at high stress levels. Fractures can still generate complex and multiple fractures when subject to high-stress conditions. Amongst, natural fissures or weak surfaces still dominate the complex fracture morphology. In the case of a higher in-situ stress level with the same stress difference value brings about a more complex hydraulic fracture morphology as a result of a smaller stress-difference coefficient. The Intersection of hydraulic fractures with multiple parallel weak surfaces creates hydraulic fractures in stepped shape, which can cause drastic fluctuations in injection pressure. The research results provide a reference for on-site deep shale reservoir stimulation and optimization of a fracturing design. [ABSTRACT FROM AUTHOR]

Faced with difficulties stemming from the complex interactions between tight gas sand bodies and fractures, when describing and identifying reservoirs, a composite reservoir model was established. By setting the supply boundary to characterize the superposition characteristics of sand bodies, a mathematical model of unstable seepage in fractured vertical wells in tight sandstone gas reservoirs was developed, considering factors such as stress sensitivity, fracture density and fracture symmetry. The seepage law and pressure response characteristics of gas wells in tight sandstone discontinuous reservoirs with stress sensitivity, semi-permeable supply boundary and complex fracture topology were determined, and the reliability of the model was verified. The research results more accurately display the pressure characteristic of a vertical well in the superimposed sand body with complex fractures and provide a more comprehensive model for tight gas production dynamic analysis and well test data analysis, which can more accurately guide the dynamic inversion of reservoir and fracture parameters.

Currently, volume fracturing of horizontal wells is the main technology for shale oil development. A large amount of fracturing fluid is injected into the formation, but the flowback efficiency is very low. Besides, the impact of fluid retention on productivity is not fully clear. There is still a debate about fast-back or slow-back after fracturing, and the formulation of a reasonable cleanup scheme is lacking a theoretical basis. To illustrate the injected-fluid recovery and production performance of shale oil wells, an integrated workflow involving a complex fracture model and oil-water production simulation was presented, enabling a confident history match of flowback data. Then, the impacts of pumping rate, slick water ratio, cluster spacing, stage spacing and flowback rate were quantitatively analyzed. The results show that the pumping rate is negatively correlated with injected-fluid recovery, but positively correlated with oil production. A high ratio of slick water would induce a quite complex fracture configuration, resulting in a rather low flowback efficiency. Meanwhile, the overall conductivity of the fracture networks would also be reduced, as well as the productivity, which indicates that there is an optimal ratio for hybrid fracturing fluid. Due to the fracture interference, the design of stage or cluster spacing is not the smaller the better, and needs to be combined with the actual reservoir conditions. In addition, the short-term flowback efficiency and oil production increase with the flowback rate. However, considering the damage of pressure sensitivity to long-term production, a slow-back mode should be adopted for shale oil wells. The study results may provide support for the design of a fracturing scheme and the optimization of the flowback schedule for shale oil reservoirs. [ABSTRACT FROM AUTHOR]

This is a case of the rarest type of talus fracture in a 28-year-old male who presented with pain in his right ankle and foot following a road traffic accident. He was unable to bear weight or walk after the injury. Imaging studies indicated fractures in the head and neck of the talus, as well as the talar dome, with a fracture line extending into the subtalar joint. The patient underwent open reduction and internal fixation using mini fragment plating and Herbert screw fixation for the osteochondral fragment. Both the intraoperative and postoperative periods were without complications. The patient was placed in plaster of Paris (POP) slab immobilization for four weeks and was advised to avoid weight-bearing while using a walker for eight weeks, after which physiotherapy commenced. Follow-up assessments showed satisfactory fracture union, good range of motion in the ankle, an excellent American Orthopedic Foot and Ankle Society (AOFAS) score, an excellent 17-Italian Foot Function Index (FFI) score, and a good Hawkins score., Competing Interests: Human subjects: Consent was obtained or waived by all participants in this study. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work., (Copyright © 2024, S et al.)

Background Context: Upper cervical complex fractures are associated with high rates of neurological damage and mortality. The Dickman's classification is widely used in the diagnosis of upper cervical complex fractures. However, it falls short of covering the full spectrum of complex fractures. This limitation hinders effective diagnosis and treatment of these injuries., Purpose: To address the diagnostic gap in upper cervical complex fractures, the study introduces a novel classification system for these injuries, assessing its reliability and usability., Study Design: Proposal of a new classification system for upper cervical complex fractures., Patient Sample: The study comprised the clinical data of 242 patients with upper cervical complex fractures, including 32 patients treated at our hospital, along with an additional 210 cases from the literature., Outcome Measures: The inter-observer and intra-observer reliability (kappa coefficient, κ) of this classification system were investigated by 3 spine surgeons. The 3 researchers independently re-evaluated the upper cervical complex fracture classification system 3 months later., Methods: The proposed classification categorizes upper cervical complex fractures into 3 main types: Type I combines odontoid and Hangman's fractures into 2 subtypes; Type II merges C1 with odontoid/Hangman's fractures into 3 subtypes; and Type III encompasses a combination of C1, odontoid, and Hangman's fractures, divided into 2 subtypes. Meanwhile, a questionnaire was administered in 15 assessors to evaluate the system's ease of use and clinical applicability., Results: A total of 45 cases (18.6%) unclassifiable by Dickman's classification were successfully categorized using our system. The mean κ value of inter-observer reliability was 0.783, indicating substantial reliability. The mean κ value of intra-observer reliability was 0.862, indicating almost perfect reliability. Meanwhile, thirteen assessors (87.7%) stated that the classification system is easy to remember, easy to apply, and they expressed intentions to apply it in clinical practice in the future., Conclusions: This system not only offers high confidence and reproducibility but also serves as a precise guide for clinicians in formulating treatment plans. Future prospective applications are warranted to further evaluate this classification system., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Rock formations naturally contain intricate internal fractures due to various environmental factors. Such fractures result in significant weakening of the mechanical properties of the rock mass. As factures have different geometric features and fill material characteristics, it is difficult to replicate their complex behavior in the laboratory. This poses a serious limitation on the experimental investigation of the mechanical properties of fractured rocks. Sand powder 3D printing (3DP) can overcome the limitations of casting methods in preparing samples with complex fractures and thus is widely applied in soft rock mechanics experiments. This paper utilizes Computer Tomography (CT) scanning to obtain the probability distribution patterns of fractures in fractured rock samples. Additionally, it combines sand powder 3DP technology to generate soft rock-like samples with internal networks of filled fractures. Uniaxial compression experiments employing digital image correlation (DIC) and acoustic emission (AE) techniques are used to investigate the mechanical properties, deformation characteristics, and fracture evolution patterns of samples with different fracture densities. By increasing the fracture density, the peak strength of the soft rock-like samples exponentially decreases, and the deformation characteristics linearly decrease. Crack propagation paths mostly follow the prefabricated fracture trajectories and loading direction. An RA-AF analysis suggests that the failure mode of the soft rock-like samples transitions from diagonal shear failure to block-shaped shear failure with increasing fracture density. These research findings represent a novel sand powder 3DP approach for studying the complex mechanics of complex fractured rocks. • A novel method to generate rock analogs with filled internal fractures is proposed. • Internal fracture density has great effect on the mechanical properties of samples. • Effect of fracture density on failure patterns are investigated with DIC and AE. [ABSTRACT FROM AUTHOR]

Particle transport in a vertical nonplanar fracture is a typical but poorly understood element in hydraulic fracturing. Particle-fluid flow in a nonplanar fracture with a narrowing width is investigated experimentally by a laboratory-scale slot, and the relevant transport mechanisms are compared with that in the planar slot. The effects of fluid flow rate, particle density, particle size, and particle volume fraction on particle distribution are investigated. The results indicate that the narrowing width complicates the slurry flow and lowers the bed coverage area. The vortex flow appears at the contraction of the cross-section as the bed grows to a threshold height and resuspends more particles further into the slot. An irregular bed with a descending stepped surface is formed due to non-uniform placement. Smaller size sands injected at a high flow rate and a low particle volume fraction build up a smaller bed. Larger and denser particles would reverse the trend. A rational model expressed by four dimensionless numbers is developed by the linear regression method to predict the coverage percentage of the particle bed. The model and experimental results provide directions to quantitatively evaluate the particle transport and distribution in a nonplanar fracture. [Display omitted] • The particle transport in a nonplanar fracture with a narrowing width is investigated by the experiment. • The dimensionless parameters are used to describe the particle distribution in nonplanar fractures. • The irregular bed with a descending stepped surface is smaller than the regular bed in the planar slot. • A correlation is developed for predicting the coverage percentage of the particle bed. [ABSTRACT FROM AUTHOR]

Introduction: Complex acetabulum fractures are a challenge for orthopedic surgeons. An evaluation of the radiographic reduction and functional result of the patients with complex fracture of the acetabulum who underwent the combined Kocher- Langenbeck and Stoppa approach was carried out. Material and methods: Cross-sectional, descriptive, ambispective design. Patients with complex acetabulum fracture who underwent the combined Kocher-Langenbeck approach plus Stoppa between 2016 and 2020 were included. The clinical records were reviewed, and the quality of the radiographic reduction was evaluated according to Matta criteria. In addition, a functional evaluation was performed with the Merle d'Aubigne and Postel scale at least 12 months after the injury. Results: Of the 31 patients, the average time between the date of fractures and the surgical intervention was 13.7 days (3-38 days). In the radiographic evaluation according to Matta criteria, 21 anatomical patients (67.7%), 7 almost anatomical (22.5%), 3 imperfect (9.6%). Functional results according to the Merle d'Aubigne and Postel scale resulted in 8 (25.8%) with excellent results, 16 (51.6%) with good results, 5 (22.5%) moderate and 2 (16.1%) poor patients. There was a statistical correlation between the age of the patient and the functional result (p = 0.029), also between the body mass index and blood loss (p = 0.027). Conclusion: The combined Kocher-Langenbeck plus Stoppa approaches are a valid alternative in these lesions, mostly with anatomical and almost anatomical radiographic results according to the Matta radiographic scale, and with excellent and good functional results according to the Merle d'Aubigne and Postel scale. [ABSTRACT FROM AUTHOR]

Massive hydraulic fracturing (MHF) is currently the most effective technology used to create fracture networks with sufficient conductivity and maximize the stimulated reservoir volume (SRV) in tight oil and gas reservoirs. The newly initiated fracture networks during MHF usually exhibit complex fracture morphology and contain intersected fractures and fracture branches. The conductivity of these fractures plays a pivotal role in determining long-term productivity. Due to the complex geometry, it is difficult to accurately evaluate intersected fracture conductivity through traditional conductivity measurement methods and devices which are designed for a single primary fracture. Unlike previous studies where fracture conductivity was measured using two rock slabs under single-direction (vertical) loading, we establish a novel conductivity measurement apparatus that can mimic different fracture intersection scenarios under both vertical and transverse loading to facilitate the evaluation of intersected fracture conductivity. Based on this apparatus, a standard conductivity measurement framework for intersected fractures under biaxial compaction conditions is also proposed, and stable and reliable conductivity testing data are obtained. Sensitivity analyses are performed to find out the controlling factors of intersected fracture conductivity and the corresponding conductivity evolution law. Results indicate that the overall intersected fracture conductivity of intersected fractures can be divided into three stages, with closure pressure increasing, videlicet, the conductivity rapid reduction stage at low closure pressure, the conductivity slow reduction stage, and the conductivity stabilization stage. Higher proppant concentration results in higher conductivity. However, the conductivity differences among cases with different proppant concentration are relatively small at high closure pressure (conductivity stabilization stage). The more complex the fracture intersecting pattern is, the higher the conductivity would be. The experimental results can provide guidance for the design of proppant placement procedure for intersected fractures.

In complex proximal humeral fractures, bone resorption of the greater tuberosity is sometimes observed after open reduction and internal fixation (ORIF). However, this has not been well characterized, and risk factors for resorption are not completely understood. We aimed (1) to identify the risk factors associated with bone resorption of the greater tuberosity and (2) to quantify the geometric and bone density characteristics associated with bone resorption using 3-dimensional computed tomography models in complex proximal humeral fractures treated with ORIF. We identified a retrospective cohort of 136 patients who underwent ORIF of 3- or 4-part proximal humeral fractures; greater tuberosity resorption developed after ORIF in 30 of these patients. We collected demographic, fracture-related, and surgery-related characteristics and performed multivariable logistic regression analysis to identify factors independently associated with the development of greater tuberosity resorption. Furthermore, we identified 30 age- and sex-matched patients by use of propensity score matching to perform quantitative fragment-specific analysis using 3-dimensional computed tomography models. After the fragment of the greater tuberosity was identified, the number of fragments, the relative fragment volume to the humeral head, and the relative bone density to the coracoid process were calculated. Measurements were compared between matched case-control groups. We found that an unreduced greater tuberosity (odds ratio [OR], 10.9; P <.001), inadequate medial support at the calcar (OR, 15.0; P <.001), and the use of an intramedullary fibular strut (OR, 4.5; P =.018) were independently associated with a higher risk of bone resorption. Quantitative fragment-specific analysis showed that greater tuberosities with a larger number of fragments (5 ± 2 vs. 3 ± 2, P =.021), smaller fragments (9.9% ± 3.8% vs. 18.6% ± 4.7%, P <.001), and fragments with a lower bone density (66.4% ± 14.3% vs. 88.0% ± 18.4%, P =.001) had higher rates of resorption. An unreduced greater tuberosity or inadequate medial support increases the risk of greater tuberosity resorption, as do a larger number of fracture fragments, smaller fragments, and lower bone density. Additionally, fibular strut grafting is an independent risk factor for tuberosity resorption. Further study is needed, but alternatives to strut grafting such as femoral head allograft may warrant serious consideration. [ABSTRACT FROM AUTHOR]

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Copyright of Natural Gas Industry is the property of Natural Gas Industry Journal Agency and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Highlights • A multiscale framework based on phase field method and XFEM is proposed. • Complex crack growth in highly heterogeneous materials is performed by MPFM. • Local physics of the heterogeneities is captured through XFEM. • MPFM is computationally more efficient as compared to conventional PFM. • MPFM provides adaptively refined mesh for an efficient crack growth simulation. Abstract In the present work, the phase field method (PFM) is integrated with multiscale extended finite element method (MsXFEM) to simulate crack growth in highly heterogeneous materials i.e. matrix with periodically distributed voids and particles. To reduce total degrees of freedom, the entire domain is partitioned into two regions of distinct meshes: region of coarse mesh and region of fine mesh. The heterogeneous region away from the crack is discretized with coarse mesh using MsXFEM, on the other hand, the region near the crack is discretized with fine mesh using standard finite elements. To save the computational time, the region away from the crack is homogenized with the help of MsXFEM whereas, in the region of fine mesh near the crack, actual heterogeneities are modelled to incorporate the local physics of the material. To further reduce the computational effort, the phase field crack evolution equations are evaluated in the region of fine mesh only. The periodically distributed heterogeneities in the region of coarse and fine mesh are modelled using XFEM. The numerical simulations are performed by considering three different types of heterogeneities (voids, particles with a perfect interface, particles with a finite interface). The effectiveness of the proposed method is validated through various numerical experiments. [ABSTRACT FROM AUTHOR]

Abstract Tight fractured carbonate reservoirs are difficult to obtain industrial oil and gas flow through conventional stimulation methods. The traditional stimulation techniques such as hydraulic fracturing and acid fracturing do not perform well in such reservoirs due to poor formation properties. Therefore, a novel stimulation technique named hybrid volume stimulation (HVS) is put forward. This technique consists of three stages, which are pad fluid fracturing, large-scale acid fracturing and proppant injection. The core idea of this technique is to create a complex fracture system with c conductivity to get further control of the reserves. In this study, laboratory tests were performed on reservoir rock samples to evaluate the stimulation effect and feasibility of HVS. Effects of pad fluid fracturing on carbonate rocks with pre-existing natural fractures were investigated. Then, features of acid dissolution on tight matrix and natural fractures in different cementing degrees were revealed. Moreover, fracture conductivity provided by different propping types was measured and the equivalent conductivity of the fracture system was calculated. The results showed that the natural fractures were extended and the induced fractures were created after pad fluid injection. Gelled acid could dissolve the cement in the partially cemented fractures and connect the fractures into one system. The propped fractures could provide enough conductivity under both high and low closure stress, while the un-propped conductivity was very limited. The acid-etched fractures might provide enough conductivity under low closure stress, however, as the closure stress increasing, it reduced to the same order of magnitude as un-propped ones. The equivalent conductivity of the fracture system was 3–4 times higher than that of the double-wing fracture, verified the feasibility and effect of HVS technique in tight fractured carbonate formations. Highlights • Hybrid volume stimulation (HVS) technique was a new technique which combines advantages of both hydraulic fracturing and acid fracturing. • This study verified that HVS could create complex fractures system. • The fracture conductivities of different propping types in complex fracture systems were systematically evaluated. • Results showed equivalent conductivity of the fracture system created by HVS is 3–4 times higher than the bi-wing fracture. [ABSTRACT FROM AUTHOR]

Tendons connect muscle to bone and play an integral role in bone and joint alignment and loading. Tendons act as pulleys that provide anchorage of muscle forces for joint motion and stability, as well as for fracture reduction and realignment. Patients that experience complex fractures also have concomitant soft tissue injuries, such as tendon damage or rupture. Tendon injuries that occur at the time of bone fracture have long-term ramifications on musculoskeletal health, yet these injuries are often disregarded in clinical treatment and diagnosis for patients with bone fractures as well as in basic science approaches for understanding bone repair processes. Delayed assessment of soft tissue injuries during evaluation of trauma can lead to chronic pain, dysfunction, and delayed bone healing even following successful fracture repair, highlighting the importance of identifying and treating damaged tendons early. Treatment strategies for bone repair, such as mechanical stabilization and biological therapeutics, can impact tendon healing and function. Because poor tendon healing following complex fracture can significantly impact the function of tendon during bone fracture healing, a need exists to understand the healing process of complex fractures more broadly, beyond the healing of bone. In this review, we explored the mechanical and biological interaction of bone and tendon in the context of complex fracture, as well as the relevance and potential ramifications of tendon damage following bone fracture, which has particular impact on patients that experience complex fractures, such as from combat, automobile accidents, and other trauma. [ABSTRACT FROM AUTHOR]

In the experimental simulation of proppant transportation in the complex fractures of shale reservoirs, the influence of many factors such as partial fracture parameters are often ignored, which cannot fully reflect the proppant transportation in the real situation. The Euler model and turbulence model were performed to numerically investigate proppant transportation and placement using the computational fluid dynamics (CFD) method, and was verified with experimental results. The formation process of proppant banks in branched, staggered, and different types of combined fractures was analyzed. The effects of the position, width, included angle of the secondary fracture, and fracture structure type on proppant transportation and placement were discussed. The simulations indicate that the proppant bank formation in the primary fracture is considered to occur in four stages and different from three stages in the secondary fractures. The proppant bank located at the node between the primary and the secondary fractures possesses good continuity, and the propagation of the proppant bank in the secondary fracture is closely related to the proppant bank state at the node in the primary fracture. The equilibrium time of the proppant bank in the secondary fracture and the primary fracture is related to the position of the secondary fracture. The total placement rate and settlement volume of proppant in the symmetrical oblique fracture is the highest for the same oblique angles, and the proppant bank morphology in the orthogonal fracture has good symmetry, improving the reliability of the fracturing design and the post-fracturing evaluation in shale reservoirs. • The proppant migration in complex staggered fracture was simulated using CFD method. • The formation process of proppant banks for complex fractures was analyzed. • The effects of fracture parameters on proppant bank morphology were investigated. [ABSTRACT FROM AUTHOR]

• An new multi-medium and multi-mechanism model for CO2 Injection and Storage. • Model verification with numerical simulator. • Effects of geological and engineering parameters on the production curve and CO 2 storage factor are studied, and the main controlling factors are analyzed. Under the background of "dual-carbon", it is strategically significant to use shale gas reservoirs for CO 2 injection and storage. Injection of CO 2 into shale formations can improve natural gas recovery and achieve effective storage of CO 2. However, due to the complex characteristics of shale reservoirs, like complex fractures and a variety of flow mechanisms, few work has been done to comprehensively consider those complex characteristics for accurate reservoir simulation of CO 2 injection and storage. Therefore, to improve this situation, this paper establishes a fully coupled model of the matrix, natural fracture and hydraulic fracture, which considers multiple mechanisms, including adsorption/desorption, diffusion, stress sensitivity of fracture and stimulated reservoir volume (SRV). The embedded discrete fracture model (EDFM) is applied to describe the transfer flow between matrix-fracture, fracture-fracture and fracture-well. The finite volume and quasi-Newton iterative methods are used to solve the model. The model's reliability and practicability are verified by matching the production history of commercial software in shale gas reservoirs. The effects of various factors on the production curve and CO 2 storage characteristics are analyzed, including adsorption/desorption, diffusion, stress sensitivity, well production pressure, CO 2 injection rate, CO 2 injection opportunity and fracture parameters. The results show that the model is reliable and practical and can be used to study the dynamic performances of enhanced shale gas recovery and CO 2 storage. [ABSTRACT FROM AUTHOR]

In order to meet the needs of the new industry technology teaching and research work, engineering practice and innovation ability development, based on the technology concept of volume fracturing for the unconventional oil and gas reservoir, a large-scale virtual simulation experimental device of proppant transportation and placement in complex fractures was developed. This device creatively achieves the simulation of branch fractures with different tendency and inclination, the different roughness and loss rate of fracture walls, the different fracture width and the horizontal well fracturing, and broaden the fractures scale and the selection range of construction parameters. The device function and automation degree have been also effectively improved, so that the device can effectively he used to cany out the experimental simulation of proppant transportation and placement for various hydraulic fracturing technologies to guide the on-site fracturing. The device has further improved the experimental teaching and scientific research methods in the relevant technical fields, and provides a richer internship, training and practice links. It will help teachers and students to carry out scientific research and innovation, and also provide an effective platform for the exploration of the “Flipped Classroom with Scientific Research Assistance” teaching mode. [ABSTRACT FROM AUTHOR]

The present paper aims at modeling complex fracture phenomena where different damaging mechanisms are involved. For this purpose, the standard one-variable phase-field/gradient damage model, able to regularize Griffith’s isotropic brittle fracture problem, is extended to describe different degradation mechanisms through several distinct damage variables. Associating with each damage variable a different dissipated fracture energy, the coupling between all mechanisms is achieved through the degradation of the elastic stiffness. The framework is very general and can be tailored to many situations where different fracture mechanisms are present as well as to model anisotropic fracture phenomena. In this first work, after a general presentation of the model, the attention is focused on a specific paradigmatic case, namely the brittle fracture problem of a 2D homogeneous orthotropic medium with two different damaging mechanisms with respect to the two orthogonal directions. Illustrative numerical applications consider propagation in mode I and II as well as kinking of cracks as a result of a transition between the two fracture mechanisms. It is shown that the proposed model and numerical implementation compares well with theoretical and experimental results, allowing to reproduce specific features of crack propagation in anisotropic materials whereas standard models using one damage variable seem unable to do so. [ABSTRACT FROM AUTHOR]