CT Scanning Technology Research Articles

Effect of different types of stimulation fluids on fracture propagation behavior in naturally fractured carbonate rock through CT scan

Acid fracturing of carbonate rock starts with formation breakdown and fracture propagation caused by stimulation fluids. The effectiveness of acid fracturing largely depends on the behavior of fracture propagation. While fracture propagation of fractured carbonate rock is greatly influenced by natural fractures and fluid types. So far, some scholars have studied the influence of nonreactive fracturing fluid on fracture propagation, but the comparison of effect between nonreactive fracturing fluid and reactive fracturing fluid on fracture propagation is rarely noticed. In this paper, true tri-axial experiments on carbonate rock (200 mm × 200 mm × 200 mm) are presented; the experiment made a comparative study on the effect of nonreactive fracturing fluid (water, guar fracturing fluid) and reactive fracturing fluid (self-generated acid, gelled acid, VES acid) on fracture propagation in fractured carbonate rock. Besides, fracture morphology was revealed through CT scan and 3D reconstruction technology. In this way, influence of natural fractures and fluid types on hydraulic fracture propagation during acid fracturing was quantitatively analyzed. Results show that these two factors indeed exert great impact on fracture propagation behavior. As acid is more conducive to connection of natural fractures, hydraulic fractures induced by acid can propagate along natural fractures after initiating from natural fractures, and the process would not be restricted by maximum horizontal stress. As a result, a longitudinal fracture parallel to the wellbore is formed. Compared with self-generated acid and gelled acid, VES acid is more liable to connect natural fractures and form complex fracture network during acid fracturing. No matter reactive or nonreactive fracturing fluid is applied to conduct fracturing experiments, hydraulic fracture propagation in carbonate rock with few natural fractures would be restricted by maximum horizontal stress, and transverse fractures perpendicular to the wellbore would be formed after fracturing. In addition, breakdown pressure of rock samples is also affected by natural fractures and fluid types. To be specific, gelled acid decreases rock's breakdown pressure to the greatest extent when numerous natural fractures exist in the rock; the breakdown pressure caused by gelled acid is only 56.7% of which caused by water. However, the gelled acid has little contribution to decrease the breakdown pressure of the carbonate rock with few natural fractures. In a word, the experiment reveals effect of stimulation fluid types on hydraulic fracture propagation in fractured carbonate rock, which provides some guidance for acid-fracturing treatment in carbonate reservoir.

Application and development of CT scanning technology in coal sector

CT scanning technology has been widely used in the observation of coal microstructures because of its advantages of non-destructive and refined visualization. In this study, the post-processing methods (image processing, 3D reconstruction, numerical simulation, etc.) of CT scan images are introduced in detail, and the application of CT in the coal sector is systematically reviewed, mainly including: coal seam gas mining (coal structure, reservoir permeability etc.); mechanical properties of coal mass damage; coal seam water injection, coal mass permeability enhancement, coal washability, etc. The application of CT in various research fields has been relatively mature. The initial research is focused on the analysis of coal mass structure, and subsequently the fractal dimension is introduced and the in-depth study of coal mass seepage is involved. At the same time, CT scanning equipment is been constantly improving to be applied to a wider range of explorations. In the future, improved image processing or equipment can increase the research accuracy, and the field of coal structure and seepage under the multi-field coupling conditions such as pressure-temperature-seepage can be explored.

Meso-structure image pre-selection method for two-dimensional finite element modeling in beam bending simulation of asphalt mixture

Finite element (FE) simulation has been widely used in conjunction with the beam bending test (BBT) to analyze the cracking behavior of asphalt mixtures. Crack propagation is significantly affected by the internal structure of an asphalt mixture. Limitations on computational resources and the complex mesostructure of asphalt mixtures have resulted in two-dimensional (2D) FE simulations being more widely used than three-dimensional simulations. However, a single 2D FE model can only reflect the mesostructural characteristics of one specimen section, precluding comparison between the simulation and laboratory test results. In this paper, X-ray CT scanning technology was used to obtain a large number of internal mesostructure images of an asphalt mixture, and image-based modeling was used to construct 2D FE models for simulating beam bending tests. An analysis of the simulated crack morphologies and positions of the models was used to propose a prediction method for the crack position based on image processing technology, and a hypothesis that the crack positions were correlated with the simulation results was put forward. This hypothesis was verified by comparing the simulation and laboratory test results. Finally, the predicted crack position (CPRP) was used to propose an image preselection method from which 2D FE models were constructed to simulate of BBT for an asphalt mixture. This method considerably reduces the number of 2D FE models required and significantly improves the calculation efficiency while ensuring the accuracy of the BBT 2D simulations.

Research on Claw Motion Characteristics and Cavitation Bubbles of Snapping Shrimp.

Snapping shrimp produces a high-speed jet through the rapid closure of the snapper claw, which stimulates the formation of cavitation bubbles of various shapes. In order to explore the fast motion characteristics of snapper claw, the formation and change process of cavitation, and the physical principles underlying the biological phenomena, the equivalent model of snapper claw was constructed through CT scanning technology. A high-speed camera was used to capture the claw's motion characteristics, thereby simulating the production of cavitation bubbles by snapping shrimp. The results show that the rotation speeds of different species of snapping shrimps are different, as well as their motion characteristics. Cavitation is formed by the interaction of the pressure drop caused by the vortex at the nozzle with the inertia of the liquid inside the socket. Under the influence of the jet, the shapes of bubbles change from ring to cone, and eventually collapse into bubble clouds.

Highly Standardized Rotational Photography of the Torso.

Over the last several decades, medical imaging technologies have proven so anatomically insightful that they have all but taken over management in many clinical situations. MRI, CT, and PET scanning technologies employ stringently controlled rotational data-harvest protocols. By contrast, standardization of visible-light imaging of human anatomy has lagged dramatically. This article is the first to present a rigidly standardized rotational protocol to photographically record human anatomy and permit subsequent analysis with less than 2% image variance.

Current role of imaging in COVID-19 infection with recent recommendations of point of care ultrasound in the contagion: a narrative review.

Radiological studies have an important role in the diagnosis and follow up of many infectious diseases. With current pandemic of Coronavirus disease 2019 (COVID-19) though the molecular analysis with reverse transcriptase polymerase chain reaction (RT-PCR) remains the cornerstone of diagnosis, the critical role of chest imaging including CT scan and baseline X-ray became apparent early in the course due to concern for less than optimal sensitivity of PCR testing. Delay in molecular diagnosis due to a shortage of testing kits and laboratory personnel also makes imaging an important modality in early diagnosis for appropriate triage and isolation decisions. CT scan technology is widely available in developed parts of the world but in developing countries, CT scanner is not widely available especially in rural settings. CT imaging usually requires patient movement to the radiology department and the scanner is not easy to disinfect. Point of care ultrasound (POCUS) has been used for many years in the assessment of critically ill patients in emergency departments and intensive care units. It is rapidly gaining popularity across many specialties and part of many general medicine training programs across the United States. It can be learned rapidly and with experienced hands, POCUS can help identify disease patterns in the lung parenchyma, and during the current pandemic has been gaining special attention. In this article, we review the most prominent imaging findings on chest X-ray and CT scan in patients with COVID-19. We also focus on the background and evolution of POCUS with studies showing the promising role of this diagnostic modality in COVID-19 infection. In addition, we describe step by step guidance on the use and disinfection of the portable ultrasound machine.

Hydraulic and thermal fracturing techniques for successful stimulation in unconventional geothermal energy recovery

Unconventional or enhanced geothermal systems (EGSs) have been recently identified as potential geothermal resources which can be utilized to extract the heat trapped in the deep geological formations. However, due to the low formation porosity in these systems, an underground heat exchanger must be artificially created to enhance reservoir permeability. A number of reservoir stimulation techniques are adopted in EGSs to enhance their permeability, including hydraulic fracturing and thermal fracturing. The aim of the present work is to provide an in-depth understanding of these reservoir stimulation techniques based on our current laboratory experimental work. Recent literature on the topic has been comprehensively reviewed, and advanced laboratory tests have been conducted to understand hydraulic and thermal fracturing techniques under reservoir conditions. Experiments were conducted utilizing the high-temperature high-pressure rock tri-axial apparatus and quenching treatments were performed by injecting cold water into granite rocks heated to different temperatures. Flow-through experiments were also conducted on intact and fractured granite rocks and the results were compared to predict production enhancement upon stimulation. CT scanning technology was employed to determine micro-scale characteristics following stimulation. Experimental work revealed that the propagation paths and apertures of hydraulic and thermal fractures are controlled by the in-situ stress and temperature and the heterogeneity of the rock matrix. Although the induced fractures contributed substantial enhancement of reservoir permeability, they were sensitive to stress and temperature changes due to the larger effective stresses and thermally induced volumetric expansion.

Pore Structure Fractal Characterization and Permeability Simulation of Natural Gas Hydrate Reservoir Based on CT Images

The gas-water two-phase seepage process is complex during the depressurization process of natural gas hydrate in a clayey silt reservoir in the South China Sea, the transport mechanism of which has not been clarified as it is affected by the pore structure. In this study, we select six clayey silt samples formed after the dissociation of natural gas hydrate in the South China Sea, employing CT scanning technology to observe the pore structure of clayey silt porous media directly. The original CT scanning images are further processed to get the binarized images of the samples, which can be used for simulation of the porosity and absolute permeability. Based on the fractal geometry theory, pore structures of the samples are quantitatively characterized from the aspect of pore distribution, heterogeneity, and anisotropy (represented by three main fractal geometric parameters: fractal dimension, lacunarity, and succolarity, respectively). As a comparison, the binarized CT images of two conventional sandstone cores are simulated with the same parameters. The results show that the correlation between porosity and permeability of the hydrate samples is poor, while there is a strong correlation among the succolarity and the permeability. Fractal dimension (represents complexity) of clayey silt samples is higher compared with conventional sandstone cores. Lacunarity explains the difference in permeability among samples from the perspective of pore throat diameter and connectivity. Succolarity indicates the extent to which the fluid in the pore is permeable, which can be used to characterize the anisotropy of pore structures. Therefore, these three fractal parameters clarify the relationship between the microstructure and macroscopic physical properties of clayey silt porous media.

Improvement of shale gas reservoir based on plasma pulse shock and frequency resonance technology

A shale gas reservoir improvement equipment applied to shale gas stimulation was developed. The device mainly includes ground control system, energy storage charging system, resonance frequency detection system, discharge switch and discharge electrode. The shale gas reservoir is improved by plasma pulse shock and frequency resonance technology. The electron density distribution at different time of the switch was simulated, and the waveform of single discharge and repetitive pulse discharge of the electrode were measured. It is shown that the electron density distribution at different time is consistent with Townsend discharge and streamer theory. And the frequency range of discharge electrode is about 0–60 Hz, meanwhile the stable discharge time is about 1 h. Furthermore, the resonance excitation can significantly improve the crack percentage and volume of shale samples calculated from porosity curve which is obtained through CT-Scan technology, also the permeability reveals an increasing trend in different directions. The results indicate that the present research might have potential application in the field of shale gas reservoir.

Thermal Property Evaluation of Porous Asphalt Concrete Based on Heterogeneous Meso-Structure Finite Element Simulation

Porous asphalt concrete (PAC) can obviously improve vehicle driving safety on rainy days and reduce environmental noise. It has been widely used in China. The existence of a large number of interconnected voids in PAC makes a significant difference in heat transfer and temperature distribution from conventional dense-graded asphalt concretes (AC). In this paper, the internal structure images of three dense-graded asphalt mixtures and one PAC were obtained by X-ray CT scanning technology, and the internal meso-structure finite element simulation models of asphalt mixtures were established by using the mapped meshing method. The temperature variations of asphalt mixture specimens during laboratory cooling and heating processes were simulated in this study, and laboratory tests were carried out to verify the simulation accuracy. Due to the simulation results, it was found that the thermal characteristics of the PAC mixture were different from those of the dense-graded asphalt mixture due to the large interconnected air void content in the PAC mixture. The temperature field in the PAC mixture was more sensitive to ambient air temperature under laboratory conditions. Moreover, in PAC specimens, temperature distributed more unevenly than in dense-grade asphalt mixtures. Therefore, it is necessary to consider the internal meso-structure of porous asphalt mixtures while simulating the temperature field in PAC specimens or pavement structures.

Effects of morphology and internal voids of copper ribs on heat transfer performance in copper foam/paraffin composite phase change materials

Thermal-enhanced composite phase change materials have broad application prospects for heat transfer and heat storage. In this paper, the effects of porosity, pore size and internal voids of copper ribs on the thermal conductivity of the copper foam/paraffin composite phase change materials were measured and analyzed in combination with a Host Disk thermal conductivity meter and industrial CT scanning technology. It is found that effective thermal conductivity of the composites decreased with the increasing porosity, and the internal voids of copper ribs was an important factor affecting the thermal conductivity, which reduced the difference between the experimental and the theoretical data from 23.1% to 0.43%. Then, the internal heat storage rate and thermal homogeneity of the composites with different copper morphology were calculated by lumped parameter method, and the effects of porosity, pore size and copper morphology on the heat storage rate and thermal homogeneity of the composites were also analyzed. Results showed that triangular prism structure had better performance than other structures.

A Design and Fabrication Method for Wood-Inspired Composites by Micro X-Ray Computed Tomography and 3D Printing

Developments in 3D printing and CT scanning technologies have facilitated the imitation of natural wood structures. However, creating composites from the elementary features of anisotropic wood structures remains a new frontier. This paper aims to investigate the potential of constructing and 3D printing mechanically customizable composites by combining anisotropic elementary models reconstructed from the micro X-ray computed tomography (μ-CT) scanning of wood. In this study, an arbitrary region of interest selected from the μ-CT scanning of a sample of Manchurian walnut (Juglans mandshurica) was reconstructed into isosurfaces that constituted the 3D model of an elementary model. Elementary models were combined to form the wood-inspired composites in various arrangements. The surface and interior structures of the elementary model were found to be customizable through adjusting the image Threshold and Surface Quality Factors during 3D volume reconstruction. Compressional simulations and experiments performed on the elementary model (digital and 3D printed) revealed that its compressive behavior was wood-like and anisotropic. Numerical analysis established a preliminary link between the arrangements of elementary models and the compressive stiffness of respective composites, showing that it is possible to control the compressive behaviors of the composites through the design of specific elementary model arrangements.

Application of Virtual Anatomy Technology in Postmortem Examination of Medical Dispute Cases.

Objective To discuss the application value of CT scanning technology in cause of death determination of medical dispute cases. Methods From July 2017 to December 2018, postmortem CT imaging data of 12 medical dispute cases were collected. CT imaging diagnosis results and anatomy findings as well as differences between antemortem and postmortem CT diagnosis were compared. The advantages and disadvantages of CT routine tests of the cadavers in terms of the diagnosis of disease and damage were analyzed. Results The comparison between CT imaging diagnosis and anatomical findings showed that CT scans had advantages in the diagnosis of disease and damage with large differences in density changes, such as atelectasis, pneumonia, calcification, fracture and hemorrhage, etc. The comparison of CT diagnosis in antemortem and postmortem examination showed that the cadavers of medical dispute cases were well preserved and that postmortem CT scan was meaningful for the diagnosis of antemortem diseases. Conclusion Virtual anatomy technology has a relatively high application value in postmortem examination of medical dispute cases. It can provide effective information for the appraisers before the autopsy and can also provide a reference for cause of death analysis when the anatomy cannot be performed.

Analysis of Internal Structure of Cement‐Stabilized Macadam Based on Industrial CT Scanning

The composition and structure of cement‐stabilized macadam (CSM) is an important factor affecting its performance. Aiming at the typical suspension dense structure and skeleton dense structure, the static pressure and vibration methods were used to prepare the CSM samples. The three‐dimensional internal structure characteristics of CSM were analyzed and studied by industrial CT scanning technology. By using digital image and 3D reconstruction technology, the structural parameters such as the number of 3D voids, the gradation of voids, the distribution of voids along the height direction, and the coefficient of variation of the proportion of coarse aggregate area were obtained. The results show that more than 80% of the voids in CSM are less than 1 mm3, and the number of large voids of skeleton dense gradation is more than that of suspension dense gradation under the two compaction methods. The distribution of internal voids along the height of CSM specimens cannot be changed by the compaction mode, but the vibration method can reduce its void ratio. Under different compaction methods, the variation coefficient of the coarse aggregate area ratio of two kinds of CSM mixture generally has the same change trend, and the vibration method can make its inner structure more uniform.

Microscopic remaining oil distribution and quantitative analysis of polymer flooding based on CT scanning

To investigate the distribution characteristics of remaining oil after polymer flooding, the core samples of different stages of water flooding and polymer flooding were scanned and imaged based on CT scanning technology. The oil, water and rock were divided into three phases by image analysis method, and the corresponding digital cores were constructed. Through the qualitative and quantitative analysis of the two-dimensional image and three-dimensional structure at the same position, the quantitative characterization of the micro-residual oil distribution in different displacement stages is finally realized. The results show that, the polymer flooding can significantly improve the sweep efficiency, which can increase the oil recovery by 11.45% compared with water flooding. The remaining oil in the pore is mainly network and multiple, and mainly network distribution at the stage of water flooding. After adding polymer, the proportion of multiple remaining oil increases significantly and becomes the main occurrence state of remaining oil. Affected by Jamin effect, multiple residual oil in the pore is difficult to be recovered because it cannot pass through the throat. The radius of this part of remaining oil is usually 1.34-1.5 times that of the throat radius. Cited as : Wang, X., Yin, H., Zhao, X., Li, B., Yang, Y. Microscopic remaining oil distribution and quantitative analysis of polymer flooding based on CT scanning. Advances in Geo-Energy Research, 2019, 3(4): 448-456, doi:10.26804/ager.2019.04.10

Using CT-scanning technology to quantify damage of the stem-boring beetle, Aphanasium australe, a biocontrol agent of Hakea sericea in South Africa

ABSTRACTThe stem-boring beetle, Aphanasium australe was introduced into South Africa in 2001 for biocontrol of Hakea sericea. It has a two-year life cycle, the majority of which is spent within the basal stem and roots of its host plant. Damage assessments indicate that A. australe is capable of killing 7-10% of trees in a Hakea stand. However, how much internal damage, and number of insects that are required to cause significant damage or death of the plant, is not known. Here, we used a novel technique – X-ray micro computed tomography (microCT) – to quantify damage in dead and live trees. We also used the technique to assess whether microCT is feasible as a means to determine percentage emergence and survival of larvae/pupae within Hakea stumps. Results showed that the technique can be used successfully to quantify damage, and that felled live trees had significantly less damage than felled dead trees. The amount of internal damage was significantly influenced by the number of insects that emerged, and by the overall size of the trees. MicroCT was able to determine with 100% accuracy the survival of insects that were either inside stumps or had emerged at the time of scanning. A complex suite of factors are responsible for death or survival of trees once infested with the biocontrol agent, and percentage internal damage to trees is not the only factor that dictates whether or not a tree will succumb to the effects of the stem-borer.

CT Image Analysis of Gastrointestinal Tumors Based on Simple Linear Iterative Cluster Algorithm

Objective: Gastrointestinal cancer is a very common disease at present. The purpose of this experiment is to use CT scanning technology and Simple Linear Iterative Cluster (SLIC) algorithm to analyze and fuse the scanning results, to explore the imaging characteristics of gastrointestinal neuroendocrine tumors by CT scanning and its application value in gastrointestinal tumors. Methods: The medical records of 25 patients with gastrointestinal tumors were selected as samples and analyzed retrospectively. Texture information fusion of CT image based on SLIC algorithm. This algorithm can fuse the texture information in the image, and then propose more targeted treatment for gastrointestinal tumors in different periods. Results: It was found that the diameter of malignant gastrointestinal tumors was more than 5 cm, and most of them occurred in the intestinal tract and the edge. The specific manifestations are blurred or lobulated, uneven density, invasion of surrounding structures and combined transfer rate. Therefore, it can be concluded that there are significant differences in CT features between benign and malignant gastrointestinal tumors. CT examination is helpful to differentiate benign and malignant tumors. Conclusion: Based on CT imaging, it can be found that the main cause of gastric neurosecretory tumors is blood-rich lesions. Gastrointestinal cancer cells of different pathological grades have different CT imaging features. CT imaging has certain value for preliminary judgment of pathological grading of patients.

The microstructure and evaluation index of reclaimed asphalt pavement

A large amount of reclaimed asphalt pavements are produced every year, recycling and utilization of them as soon as possible can not only reduce the exploitation of natural aggregate resources and protect the natural ecological environment, but also help to solve the problem of reclaimed asphalt pavements. However, the complexity of structures and the lack of research on performance index have led to few successful applications about reclaimed asphalt pavements. In this paper the microstructure of reclaimed asphalt pavement was studied based on the X-ray CT scanning technology, by which the key factor in the evaluation of reclaimed asphalt pavement was found through analyzing the micrographs by VG Studio MAX image processing tool. The microstructure and evaluation index of reclaimed asphalt pavement provide a good foundation for application.

Effects of fiber orientation and content on the static and fatigue behavior of SFRC by using CT-Scan technology

The effects of the fiber orientation and content on the behavior of steel fiber-reinforced concrete (SFRC) under static and cyclic compressive loads are studied using the computed tomography (CT) technique, and the resistance mechanisms of the fibers are carefully observed. The results suggest that the intrinsic scatter in the fatigue life could be partially explained by the essential scatter in the fiber orientation and content. On the contrary, no relationship is observed between the intrinsic scatter in compressive strength and fiber orientation and content, which suggests that the compressive strength of the specimens is mainly due to their concrete matrix.

The process of 3D printed skull models for anatomy education

In general, the 3 D printed medical models are made based on virtual digital models obtained from machines such as the computed tomography scanner. However, due to the limited accuracy of CT scanning technology, which is usually 1 millimeter, there are differences between scanned results and the real structure. Besides, the collected data can hardly be printed directly because of some errors in the model. In this paper, we present a general and efficient procedure to process the digital skull data to make the printed structures meet the requirements of anatomy education, which combines the use of five 3 D manipulation tools and the procedure can be finished within 6 hours. Then the model is printed and compared with the cadaveric skull from frontal, left, right and anterior views respectively. The printed model can describe the correct structure and details of the skull clearly, which can be considered as a good alternative to the cadaveric skull. The manipulation procedure presented in this study is an easily available and cost-effective way to obtain a printed skull model from the original CT data, which has a considerable economic and social benefit for the medical education. The steps of the data processing can be performed easily. The cost for the 3 D printed model is also low. Outcomes of this study can be applied widely in processing skull data.