bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Investigation into Proppant Transport in a Tortuous Fracture During Supercritical CO2 Fracturing
Authors: Zheng Yong , Wang Haizhu , Liu Mingsheng , Tian Ganghua , Yang Bing 
Published: September 2022

ABSTRACT:
In this paper, laser topography scanning technology is used to extract the fracture morphology after supercritical CO2 fracturing to generate a tortuous fracture model. Then a supercritical CO2 slurry flow model is established based on CFD-DEM coupling method, and the proppant transport in the tortuous fracture is simulated. The flow and proppant transport characteristics of supercritical CO2 slurry in tortuous fractures were analyzed, and the effects of injection velocity, injection temperature and injection pressure on proppant transport and distribution in tortuous fractures were investigated. The results show that the flow of supercritical CO2 slurry in tortuous fractures forms curved dominant channels compared to planar fractures, and the formed proppant dune is not uniformly distributed within the fractures. Low injection velocity in tortuous fractures is more likely to cause sand plugging, and increasing the injection velocity can weaken the effect of fracture structure on proppant transport. Low injection temperature and high injection pressure facilitates the transport and distribution of proppant in tortuous fractures. The results of the study contribute to an in-depth understanding of the flow behavior of supercritical CO2 slurry in tortuous fractures.

1. INTRODUCTION
Unconventional oil and gas reservoirs are characterized by low reservoir porosity, poor fluid permeability and low natural production capacity, making it difficult to develop them on a large scale by conventional extraction methods. Thanks to the emergence and development of hydraulic fracturing technology, the process of commercial development of unconventional oil and gas, such as shale gas, has been greatly accelerated (Denney, 2010). However, with the wide application of hydraulic fracturing technology, it also faces a series of challenges such as water consumption, reservoir clay expansion, and groundwater contamination (Hyman et al., 2016; Liu, Jiang, Huang, and Sugimoto, 2018).
CO2 plays an important role in enhanced oil recovery (EOR) because of its good solubility and strong extraction ability in crude oil, which can significantly reduce crude oil viscosity, swell and increase capacity, and reduce interfacial tension by mixing phase with crude oil in multiple contacts(Hill, Li, and Wei, 2020; Li et al., 2017). When CO2 is injected into the reservoir, it changes to a supercritical state at the temperature and pressure conditions of the reservoir. Supercritical CO2 has shown great advantages as a fracturing fluid in eliminating reservoir damage, improving shale gas recovery and storing CO2 in the underground, and is a new waterless fracturing technology with broad application prospects(Middleton et al., 2015; Yang et al., 2021).
Stability Analysis of Shotcrete Lining for a Mine Shaft Using the Finite-Discrete Element Method
Authors: Naseri S. , Bahrani N. 
Published: September 2022

ABSTRACT:
This paper aims to provide insights into the effectiveness and failure mechanism of shotcrete lining in mine developments. For this purpose, a two-dimensional numerical program based on the Finite-Discrete Element Method (FDEM) was utilized to simulate an instrumented section of a 10-m diameter mine shaft at a depth of 1.2 km in an average quality rock mass. The shaft wall was supported by shotcrete and concrete liners installed at 3 m and 12 m behind the face, respectively. However, only shotcrete support was considered in the numerical simulations. The shotcrete liner was modelled as a material with a thickness of 50 mm and calibrated based on the mechanical properties of early-age fiber reinforced shotcrete obtained from available laboratory test results and empirical equations. The rock material near the modelled shaft was calibrated against the extensometer measurement data. It was found that the shotcrete liner fails due to bending caused by the shaft wall convergence and local rock mass bulking. Therefore, for the rock mass and in situ stress conditions representative of the mine shaft, it is concluded that the addition of a permanent support element, such as a concrete liner, is necessary for the long-term stability of the shaft.

1. INTRODUCTION
Underground mines aim to reach deep orebodies by enhancing the advance rate of access developments while maintaining safe workplaces. Underground lateral (drifts) and vertical (shafts) developments are excavated using two main methods: drill and blast and mechanized excavations. The application of mechanized excavation machinery leads to an increase in the overall performance and thus the net present value of the projects. While mechanized excavation is ideal for moderately strong to weak rock masses, the drill and blast method has been used in a wide range of rock mass conditions [1]. Although the mining industry has been investigating mechanized excavation as an alternative method in hard rocks, the conventional drill and blast excavation method is still the norm in modern-day developments in underground mines [2].
Conductivity Evaluation of Cross Propped Fractures in Shale Reservoirs
Authors: Ma L. , Lu C. , Guo J. C. , Li X. Y. , Luo Y. , Wang K. J. 
Published: September 2022

ABSTRACT:
Volume fracturing is a key technology for shale gas development. It connects hydraulic fractures and natural fractures to form a large-scale cross propped fracture network. The conductivity of cross propped fractures is the key to the effect of shale volume fracturing. Based on the Kozeny model, the conductivity of a single fracture is calculated, and the conductivity of the single fracture is corrected by experimental data, taking into account the effect of formation closure stress. Based on the similarity principle of hydropower, an evaluation model for the conductivity of cross propped fractures is proposed. On the basis of the numerical simulation results of proppant transportation, the factors affecting the conductivity of cross propped fractures are analyzed. The results show that the proppant falls at a low velocity into the narrow natural fracture, and then moves slowly forward in the form of a creep in the fracture, where it is transported for a short distance. For wide natural fractures, the proppant is suspended into the fracture at a greater velocity and transported over a longer distance, forming a "tall and long" proppant dune morphology. When the natural fracture width ratio increases, the proppant is placed more unevenly in the cross fractures, the seepage resistance of proppant dunes in hydraulic fractures gradually increases, the seepage resistance in natural fractures has no obvious change, the total seepage resistance of cross fracture is greater, and the conductivity of the fracture is smaller. The numerical calculation model is used to evaluate the conductivity of cross propped fractures, which provides theoretical guidance for the optimization of shale gas volume fracturing schemes.

1. INTRODUCTION
As a kind of clean energy, Chinese shale gas will break through 2 × 1012 m3 and 200 × 108 m3 respectively in proven geological reserves and total annual production in 2020. Increasing shale gas exploration and development under the "dual carbon" target is an important guarantee to ensure energy security and alleviate environmental problems (Long et al., 2021; Zhang et al., 2021). At present, the development of shale gas reservoirs at home and abroad usually adopts volume fracturing technology. Through the construction method of "fast injection velocity + large liquid volume + large sand volume", hydraulic fractures and natural fractures are connected, so as to realize the effective placement of proppant in the fractures, form large-scale cross propped fractures, and improves fluid seepage channels, thereby greatly increasing gas well productivity (Lu et al, 2019a; Lu et al., 2019b; Zhang, 2022).
Application of Geomechanical Modeling in the Study of Loss Mechanism of Fractured Formation—A Case Study from Bohai Bay, China
Authors: Cai Wenjun , Deng Jingen , Feng Yongcun , Wang Yangang , Ma Chenyun 
Published: September 2022

ABSTRACT:
Bohai A Oilfield is a fractured oil and gas field, and the lost circulation problems in the non-reservoir and the reservoir are severe during the drilling process. The vicious lost circulation problem in the A Oilfield is characterized by the suddenness of the lost circulation event, the uncertainty of the lost circulation layer, the large amount of mud loss, and the long plugging time. This type of lost circulation problem has seriously plagued the drilling speed-up work of the A Oilfield. To clarify the loss mechanism of the non-reservoir and the reservoir, this paper consults and analyzes all relevant data (geology, logging records, drilling fluid characteristics, drill cuttings test results, and so on) of the A Oilfield. Based on the well data and seismic data, a set of analysis methods for the loss mechanism of fractured formations are established by the geomechanical modeling method. This work establishes the spatial distribution of essential parameters such as the three-dimensional elastic modulus, the three-dimensional Poisson’s ratio, and the three-dimensional pore pressure of the A Oilfield. Based on the finite element method, the three-dimensional stress field model of the A Oilfield is calculated by constructing a heterogeneous-pore-elastoplastic model. And then, the lost circulation pressure of the reservoir and non-reservoir of Bohai A Oilfield is also calculated, respectively. The main lost circulation factors in the entire oilfield area are determined by the complex working conditions and the three-dimensional lost circulation pressure calculation results. The results show that the loss mechanism of the non-reservoir is insufficient pressure bearing capacity of the fracture zone. The loss mechanism of buried-hill reservoirs is a prominent, very narrow safe drilling window in the fracture area.

1. INTRODUCTION
The Bohai A Oilfield is about 55 kilometers away from Tanggu district in Tianjin, with an average water depth of 14m. According to the drilling data, the strata in this area developed from old to new in sequence: Paleozoic Formation (Pz), Shahejie Formation (E2s), Dongying Formation (E3d), Guantao Formation (N1g), Minghuazhen Formation (N1m). The reservoir of Bohai A Oilfield is the Pz Formation. The interpretation result of the geological horizon is shown in Fig. 1. There are many faults and fractures in this Oilfield. The geological conditions have brought significant challenges to drilling operations.
A Review of Tensile Strength Measurement in Rock with Laminations/Bedding and Its Implication on Rock Mechanical Properties and Fracture Pressure Gradient Estimation
Authors: Moronkeji D. A. , Wolfe C. A. 
Published: September 2022

ABSTRACT:
The tensile strength (TS) has been used extensively in estimating the unconfined compressive strength of a rock formation when the number of UCS measurements are limited. A well-known method of determining the TS of a rock sample is the Brazilian tensile strength (BTS) test. In horizontal rock samples with bedding planes (BP), lower horizontal tension at failure typically occurs in a BTS test when loading the sample parallel to bedding (PLTB) versus perpendicular to bedding (PDTB). This is because bedding activation failure mode dominates in PLTB versus typical central fracture failure mode in PDTB. Numerous studies have been done on BTS; however, this study is a review of the implication of the differences in BTS obtained between PLTB and PDTB loading to observe the effect of BP. In this review, we measured BTS tests and observed variation between PLTB and PDTB measurements. These differences have implications on the prediction of rock mechanical properties and fracture pressure gradient estimation. This study shows an overall good fit to a relationship existing to derive a useful correlation between PLTB and PDTB tensile strength measurements that can be used in unconventional shale resources when the amount of core samples is limited or restricted to horizontal rotary sidewall cores.

1. INTRODUCTION
The drilling and completion of underground wells requires a thorough knowledge of the fracture gradient. In general, during drilling operations the fracture gradient is taken to be the maximum equivalent circulation density a well can handle to avoid drilling fluid losses, while during completion operations the fracture gradient could be defined as the formation breakdown pressure or the fracture propagation pressure. The fracture gradient varies along the length of a given wellbore and is a function of the effective in-situ stresses, pre-existing fractures, the wellbore trajectory, and the tensile strength of the rock (Aadnøy, 1988). The wellbore trajectory can be obtained via a well survey and there are numerous techniques to estimate the effective in-situ stresses along the well path that will not be revisited here. High resolution image logs can be obtained and interpreted to quantify the pre-existing fracture density as well as the strike and dip of the fractures. The tensile strength, however, can only be obtained from direct or indirect tensile strength laboratory measurements.
Uncommon Sense
Authors: Leonard Craig 
Published: September 2022

An examination of Herbert Marcuse's political claim for the aesthetic dimension, focusing on defamiliarization as a means of developing radical sensibility.
In Uncommon Sense, Craig Leonard argues for the contemporary relevance of the aesthetic theory of Herbert Marcuse—an original member of the Frankfurt School and icon of the New Left—while also acknowledging his philosophical limits. His account reinvigorates Marcuse for contemporary readers, putting his aesthetic theory into dialogue with antiracist and anti-capitalist activism. Leonard emphasizes several key terms not previously analyzed within Marcuse's aesthetics, including defamiliarization, anti-art, and habit. In particular, he focuses on the centrality of defamiliarization—a subversion of common sense that can be a means to the development of what Marcuse refers to as “radical sensibility.”
Leonard brings forward Marcuse's claim that the aesthetic dimension is political because of its refusal to operate according to the repressive common sense that establishes and maintains relationships dictated by advanced capitalism. For Marcuse, defamiliarization is at the center of the aesthetic dimension, offering the direct means of stimulating its political potential. Leonard expands upon Marcuse's aesthetics by drawing on the work of Sylvia Wynter, going beyond Marcuse's predominantly European and patrilineal intellectual framework—while still retaining his aesthetic theory's fundamental characteristics—toward a human dimension requiring decolonial, feminist, antiracist, and counterpoetic perspectives.
The Dutch obstetric intervention study — variations in practice patterns
Authors: Heres M.H.B. , Pel M. , Elferink‐Stinkens P.M. , Van Hemel O.J.S. , Treffers P.E. 
Published: July 2002

AbstractObjective: To compare obstetric intervention rates between Dutch hospitals. Methods: A total of 28 934 hospital births under secondary care (specialist care for medium‐/high‐risk pregnancies) in 1990 were analyzed in a stratified, random sample of Dutch hospitals based on the records of the Dutch Netherlands perinatal database. Comparisons were made of the intervention rates between hospitals. Results: The intervention rates of the various hospitals differed widely. The most striking difference was in the cesarean section (CS) rate for non‐vertex first twins, with a range of 0–100% and a mean rate of 47.6%. On average a CS for a term breech was performed in 30.8% of cases and sedation or analgesics were administered in 16.2% of cases. The mean rate of episiotomy for a term breech was 71.5%, the lowest rate being 18.8%. Conclusion: Our results show relatively low intervention rates with considerable interhospital variation.
Influence of Baculovirus‐Host Cell Interactions on Complex N‐Linked Glycosylation of a Recombinant Human Protein
Authors: Joshi Lokesh , Davis Thomas R. , Mattu Taj S. , Rudd Pauline M. , Dwek Raymond A. , Shuler Michael L. , Wood H. Alan 
Published: July 2002

AbstractThe conditions required for mammalian‐type complex N‐linked glycosylation of human proteins produced in insect cells with the baculovirus expression vector system were investigated. Marked alterations to N‐linked glycosylation of human placental secreted alkaline phosphatase (SEAP) were observed with different baculovirus species, insect cell lines, and cell culture media. When a recombinant Autographa californica nucleopolyhedrovirus (AcMNPV) was used to produce SEAP in Trichoplusia ni (Tn‐4h) cells cultured in serum‐free medium, structural analyses indicated <1% hybrid and no complex oligosaccharides attached to SEAP, a typical result with the baculovirus expression vector system. However, when fetal bovine serum was added to the culture medium, 48 ± 4% of the oligosaccharides were hybrid or complex (but asialylated) glycans. When a recombinant T. ni nucleopolyhedrovirus (TnSNPV) was similarly used to express SEAP in Tn‐4h cells cultured in serum‐containing medium, only 24 ± 3% of the glycans contained terminal N‐acetylglucosamine and/or galactose residues. In contrast, SEAP produced in Sf9 cells grown in serum‐containing medium with AcMNPV contained <1% hybrid oligosaccharides and no complex oligosaccharides. The results illustrate that baculovirus type, host cell type, and the growth medium all have a strong influence on the glycosylation pathway in insect cells, resulting in significant alterations in structures and relative abundance of N‐linked glycoforms. Although the addition of sialic acid residues to the SEAP glycans was not detected, possible approaches to obtain sialylated glycans are discussed.
Stability of Lactate Dehydrogenase in Metal‐Catalyzed Oxidation Solutions Containing Chelated Metals
Authors: Madurawe Rapti D. , Lin Zhanglin , Dryden Phillip K. , Lumpkin Janice A. 
Published: July 2002

AbstractThe role of metal chelators in altering the reactivity of metal‐catalyzed oxidation solutions containing iron or copper, ascorbate, and hydrogen peroxide was evaluated by measuring the loss of enzymatic activity of lactate dehydrogenase (LDH) and the formation of hydroxyl radicals. The chelators used were iminodiacetic acid, nitrilotriacetic acid, ethylenediaminetetraacetic acid, bicinchoninic acid, dihydrobenzoic acid, desferroxalamine mesylate, and phytate. All of the chelators tested at a 10:1 chelator:metal ratio afforded some protection to LDH compared to the unchelated system. Selected chelators that afforded only partial protection to LDH were able to provide nearly complete protection at higher chelator:metal ratios. This protection is likely attributable to the chelators' ability to remove surface‐bound metals and, thereby, reduce “site‐specific” oxidation. Many metal−chelator pairs generated hydroxyl radicals. The rate and amount of hydroxyl radicals formed varied depending on the metal−chelator pair. Although large amounts of hydroxyl radicals did not always result in increased protein inactivation, the absence of radicals was required for complete protein protection. The chelator to metal ratio required to eliminate hydroxyl radical formation varied widely with the metal−chelator pair and was unusually high in some cases. The results suggest that metal−chelator pairs (of various ratios) can be screened for hydroxyl radical formation and that those which show no radical formation are expected to protect the protein. No definitive conclusions can be drawn concerning the stability of LDH in solutions capable of producing hydroxyl radicals as the rate and extent of hydroxyl radical formation was not correlated simply to LDH inactivation under the conditions studied.
A Novel Full‐Scale Flat Membrane Bioreactor Utilizing Porcine Hepatocytes: Cell Viability and Tissue‐Specific Functions
Authors: De Bartolo L. , Jarosch‐Von Schweder G. , Haverich A. , Bader A. 
Published: July 2002

AbstractWhen designing an extracorporeal hybrid liver support device, special attention should be paid to providing the architectural basis for reconstructing a proper cellular microenvironment that ensures highest and prolonged functional activity of the liver cells. The common goal is to achieve high cell density culture and to design the bioreactor for full‐scale primary liver cell cultures under adequate mass transfer conditions. An important aim of this study was to evaluate the biochemical performance of a flat membrane bioreactor that permits high‐density hepatocyte culture and simultaneously to culture cells under sufficient oxygenation availability conditions comparable to the in vivo‐like microenvironment. In such a bioreactor pig liver cells were cultured within an extracellular matrix between oxygen‐permeable flat‐sheet membranes. In this investigation we used a novel scaled‐up prototype consisting of up to 20 modules in a parallel mode. Each module was seeded with 2 × 108 cells. Microscopic examination of the hepatocytes revealed morphological characteristics as found in vivo. Cell concentration increased in the first days of culture, as indicated by DNA measurements. The performance of the bioreactor was monitored for 18 days in terms of albumin synthesis, urea synthesis, ammonia elimination, and diazepam metabolism. The ability of the hepatocytes to synthesize albumin and urea increased during the first days of culture. Higher rates of albumin synthesis were obtained at day 9 and remained at a value of 1.41 pg/h/cell until day 18 of culture. The rate of urea synthesis increased from 23 ng/h/cell to 28 ng/h/cell and then remained constant. Cells eliminated ammonia at a rate of about 56 pg/h/cell, which was constant over the experimental period. Hepatocytes in the bioreactor metabolized diazepam and generated three different metabolites: nordiazepam, temazepam, and oxazepam. The production of such metabolites was sustained until 18 days of culture. These results demonstrated that the scale‐up of the bioreactor was assessed, and it could be demonstrated that the device design aimed at the reconstruction of the liver‐specific tissue architecture supported the expression of liver‐specific functions of primary pig liver cells.
INFERIOR VENA CAVAL RESECTION WITH AUTOGENOUS PERITONEO‐FASCIAL PATCH GRAFT CAVAL REPAIR: A NEW TECHNIQUE
Authors: Chin P. T. , Gallagher P. J. , Stephen M. S. 
Published: July 2002

Background: In the course of oncological surgery, resection of the inferior vena cava (IVC) may be required to obtain an adequate resection margin and to offer the best opportunity of cure. The remaining defect in the IVC may be managed by: (i) primary repair which may lead to subsequent narrowing of the lumen, possibly leading to turbulent flow and thrombus formation; (ii) patch grafting of the defect, which may prevent narrowing. Several synthetic and biosynthetic materials are available as patch grafts and autologous pericardium has also been used. Methods: The harvesting and use of the autogenous peritoneo‐fascial (APF) graft as an alternative caval patch graft material in the management of defects in the caval wall is proposed. Autogenous peritoneo‐fascial caval patch graft repair in six patients was undertaken. Results: One patient with leiomyosarcoma secondaries in the liver eventually succumbed to the disease. The other five patients are clinically well with no evidence of IVC obstruction or venous aneurysms. Conclusion: Preliminary results show that this new technique of utilizing an APF patch graft for caval repair is clinically a suitable alternative to current biosynthetic and synthetic materials and may in fact be superior in many aspects.