Analysis of Hydraulic Fracture Propagation and Well Performance using Geomechanical Models and Fast Marching Method

Successful exploitation of unconventional resource plays relies on the massive hydraulic fractures which provide high conductive paths and large contact area between formation and wellbore. The pursuit of efficiency and cost savings drives the industry to implement the strategies that utilize more closely spaced hydraulic fractures, as well as multiple horizontal wells with reduced spacing, to maximize the production from unconventional reservoirs with ultra-low permeability. One rising challenge from this trend is to find the optimized spacing between fracture clusters, fracture stages, and fractured horizontal wells so that the potential fracture interference could be minimized. This interference could occur at different scales within lifecycle of exploration, from stress interference in completion stage to pressure interference in production stage. Thus, to systematically study these issues, both geomechanical model and reservoir model are required. In this dissertation, a finite element based geomechanical model and a fast marching based reservoir model are customized to address these emerging problems in unconventional reservoir development. First, we present a comprehensive study of various factors that affect the performance of refracturing operation, such as fracturing spacing, permeability, proppants and refracturing time, by using a cohesive zone finite element based model that can capture the effect of depletion on fracture propagation. The well performance are evaluated under two different refracturing designs: refracturing new or existing perforations. Based on the simulation results, their respective suitability have been concluded. Second, we integrate fracture propagation, reservoir flow and wellbore hydraulics to evaluate the stress shadow effect and efficiency of limited entry perforations during multiple simultaneous fracture propagation within a single fracture stage. Simulation results provide insights to the selection of operational parameters such as cluster spacing, number of clusters and perforations, which can be modified accordingly to deal with the fracture interference and thus promote the uniform stimulation in the formation. Last, to study the production interference between wells, on top of current fast marching based reservoir simulation workflow, we proposed an approach to extend its applicability from transient to boundary-dominated flow regime, as well as a new partition method to identify the respective drainage volume of individual well. This partition criterion utilizes asymptotic pressure solution and results in a good approximation to the conventional streamline tracing method. The supremacy of numerical efficiency has been further demonstrated with numerical experiments

Analysis of the “631” geological disaster early warning mode and case studies in Hunan Province

Rainfall is the primary trigger for geological disasters, yet accurately predicting the timing and distribution of rainfall remains challenging, contributing to the high false alarm rates of traditional short-term geological disaster early warning systems. Located in south-central China, Hunan Province experiences abundant rainfall and relatively fragile geological conditions, making it susceptible to frequent geological disasters. To address the escalating challenges of geological disaster prevention and control, a “631” progressive geological disaster meteorological risk early warning model has been constructed based on years of early warning work experience in Hunan Province. This early warning model is technically supported by the comprehensive geological disaster prevention and control information system of Hunan Province, and is based on accurate short-term rainfall forecasts and real-time precipitation. It establishes an early warning and response mechanism, issuing warning six hours in advance to forecast rainfall areas, three hours in advance for general warnings, one hour in advance for responses, and thirty minutes in advance for further response. Currently, this early warning model has been widely applied in geological disaster prevention and control efforts across the province, and greatly improving the efficiency and accuracy of early warnings. In early June 2022, Hunan Province encountered an unprecedented heavy rainfall event that exceeded historical records, and geological disasters occurred in clusters. Through the application of this early warning model, Hunan ranked first nationwide in the number of evacuees and avoidance measures implemented in 2022, demonstrating significant disaster prevention results

Event-based pedestrian detection using dynamic vision sensors

Pedestrian detection has attracted great research attention in video surveillance, traffic statistics, and especially in autonomous driving. To date, almost all pedestrian detection solutions are derived from conventional framed-based image sensors with limited reaction speed and high data redundancy. Dynamic vision sensor (DVS), which is inspired by biological retinas, efficiently captures the visual information with sparse, asynchronous events rather than dense, synchronous frames. It can eliminate redundant data transmission and avoid motion blur or data leakage in high-speed imaging applications. However, it is usually impractical to directly apply the event streams to conventional object detection algorithms. For this issue, we first propose a novel event-to-frame conversion method by integrating the inherent characteristics of events more efficiently. Moreover, we design an improved feature extraction network that can reuse intermediate features to further reduce the computational effort. We evaluate the performance of our proposed method on a custom dataset containing multiple real-world pedestrian scenes. The results indicate that our proposed method raised its pedestrian detection accuracy by about 5.6–10.8%, and its detection speed is nearly 20% faster than previously reported methods. Furthermore, it can achieve a processing speed of about 26 FPS and an AP of 87.43% when implanted on a single CPU so that it fully meets the requirement of real-time detection

Actual Application of a H 2

To evaluate the actual performance of the H2-based polyvinyl chloride hollow fiber membrane biofilm reactor (HF-MBfR), we used HF-MBfR to remove nitrate from the nitrate contaminated groundwater with the dissolved oxygen (~6.2 mg/L) in Zhangqiu city (Jinan, China). The reactor was operated over 135 days with the actual nitrate contaminated groundwater. The result showed that maximum of nitrate denitrification rate achieved was over 133.8 g NO3--N/m3d (1.18 g NO3--N/m2d) and the total nitrogen removal was more than 95.0% at the conditions of influent nitrate 50 mg/L, hydrogen pressure 0.05 MPa, and dissolved oxygen (DO) 6.2 mg/L, with the nitrate in effluent under the value limits of drinking water. The fluxes analysis showed that the electron-equivalent fluxes of nitrate, sulfate, and oxygen account for about 81.2%, 15.2%, and 3.6%, respectively, which indicated that nitrate reduction could consume more electrons than that of sulfate reduction and dissolved oxygen reduction. The nitrate reduction was not significantly influenced by sulfate reduction and the dissolved oxygen reduction. Based on the actual groundwater quality on site, the Langelier Saturation Index (LSI) was 0.4, and the membrane could be at the risk of surface scaling

Porous chitosan microspheres as microcarriers for 3D cell culture

The final publication is available at Elsevier via https://doi.org/10.1016/j.carbpol.2018.09.021 © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/Highly porous chitosan microspheres (CSM) were prepared through emulsion-based thermally induced phase separation (TIPS) without using toxic crosslinkers and chemical porogenic agents other than ice. The CSM had an average diameter of ∼150 μm with interconnected pores varying from 20∼50 μm in size. Due to their excellent biocompatibility and unique porous structure, high-performance hepatocyte culture in three-dimensional (3D) space was achieved using the CSM as microcarriers, as cell growth also took place within the internal pores of the CSM, besides their external surface, and multidirectional cell–cell interactions were observed. Enhanced cellular activity and functions were obtained with the CSM microcarriers as compared with 2D cell culture. It is believed that these CSM microcarriers provide a promising platform for 3D cell culture in vitro.National Natural Science Foundation of China General Program (Nos. 51803067, 21574050 and 21774039) China Postdoctoral Science Foundation (General Program, No. 2015M580640) Science and Technology Support Plan in Jiangsu Province, China (BE2014684) Independent innovation research funding of Huazhong University of Science and Technology (2014XJGH009

DiDang Tang Inhibits Endoplasmic Reticulum Stress-Mediated Apoptosis Induced by Oxygen Glucose Deprivation and Intracerebral Hemorrhage Through Blockade of the GRP78-IRE1/PERK Pathways

DiDang Tang (DDT), a Chinese traditional medicine formula, contains 4 Chinese traditional medicine substances, has been widely used to treat intracerebral hemorrhage (ICH) patients. However, the molecular mechanisms of DDT for protecting neurons from oxygen and glucose deprivation (OGD)-induced endoplasmic reticulum (ER) stress and apoptosis after ICH still remains elusive. In this study, high-performance liquid chromatography fingerprint analysis was performed to learn the features of the chemical compositions of DDT. OGD-induced ER stress, Ca2+ overload, and mitochondrial apoptosis were investigated in nerve growth factor -induced PC12, primary neuronal cells, and ICH rats to evaluate the protective effect of DDT. We found that DDT treatment protected neurons against OGD-induced damage and apoptosis by increasing cell viability and reducing the release of lactate dehydrogenase. DDT decreased OGD-induced Ca2+ overload and ER stress through the blockade of the glucose-regulated protein 78 (GRP78)- inositol-requiring protein 1α (IRE1)/ protein kinase RNA-like ER kinase (PERK) pathways and also inhibited apoptosis by decreasing mitochondrial damage. Moreover, we observed similar findings when we studied DDT for inhibition of ER stress in a rat model of ICH. In addition, our experiments further confirmed the neuroprotective potential of DDT against tunicamycin (TM)-induced neural damage. Our in vitro and in vivo results indicated that the neuroprotective effect of DDT against ER stress damage and apoptosis occurred mainly by blocking the GPR78-IRE1/PERK pathways. Taken together, it provides reliable experimental evidence and explains the molecular mechanism of DDT for the treatment of patients with ICH

Biodegradable double-network GelMA-ACNM hydrogel microneedles for transdermal drug delivery

As a minimally invasive drug delivery platform, microneedles (MNs) overcome many drawbacks of the conventional transdermal drug delivery systems, therefore are favorable in biomedical applications. Microneedles with a combined burst and sustained release profile and maintained therapeutic molecular bioactivity could further broaden its applications as therapeutics. Here, we developed a double-network microneedles (DN MNs) based on gelatin methacrylate and acellular neural matrix (GelMA-ACNM). ACNM could function as an early drug release matrix, whereas the addition of GelMA facilitates sustained drug release. In particular, the double-network microneedles comprising GelMA-ACNM hydrogel has distinctive biological features in maintaining drug activity to meet the needs of application in treating different diseases. In this study, we prepared the double-network microneedles and evaluated its morphology, mechanical properties, drug release properties and biocompatibility, which shows great potential for delivery of therapeutic molecules that needs different release profiles in transdermal treatment

The Automorphism Groups of Minimal Infinite Circulant Digraphs

AbstractAn infinite circulant digraph is a Cayley digraph of the cyclic group ofZof integers. Here we prove that the full automorphism group of any strongly connected infinite circulant digraph over minimal generating set is just the group of translations ofZ.We also present some related conjectures