Study on imbibition during the CO2 enhanced oil recovery in fractured tight sandstone reservoirs

CO2 enhanced oil recovery (CO2-EOR) is a key technology for improving the oil recovery of fractured tight reservoirs, and imbibition has been recognized as an important mechanism for oil recovery in low-permeability reservoirs. To clarify the imbibition role and influencing factors during the CO2-EOR process in fractured tight oil reservoirs and also improve the EOR mechanism, a high-temperature and high-pressure CO2 imbibition experiment was performed based on the nuclear magnetic resonance technology. The results show that high pressure and high permeability are beneficial to imbibition efficiency. The salinity of the imbibition fluid is not very sensitive to the imbibition recovery. In addition, the CO2 increases the imbibition speed and can also significantly improve the production rate and oil recovery. It is beneficial to increase the CO2 concentration to shorten the imbibition equilibrium time and enhance oil recovery. According to the results of the nuclear magnetic resonance study, although the nanopore can provide a greater imbibition force, the oil flow resistance is also larger, but CO2 can reduce the flow resistance of oil and be conducive to oil production in smaller pores. The inclusion of imbibition into the research category of CO2-EOR mechanism will be more in line with field practice and more scientific in fractured tight reservoirs, thus providing theoretical support for the development and improvement of the CO2-EOR technology.Document Type: Original articleCited as: Wang, Y., Shang, Q., Guo, J., Zhou, L. Study on imbibition during the CO2 enhanced oil recovery in fractured tight sandstone reservoirs. Capillarity, 2023, 7(3): 47-56. https://doi.org/10.46690/capi.2023.06.0

Seven broad absorption line quasars with excess broad band absorption near 2250 \AA

We report the discovery of excess broad band absorption near 2250 A (EBBA) in the spectra of seven broad absorption line (BAL) quasars. By comparing with the statistical results from the control quasar sample, the significance for the detections are all above the > 4{\sigma} level, with five above > 5{\sigma}. The detections have also been verified by several other independent methods. The EBBAs present broader and weaker bumps at smaller wavenumbers than the Milky Way, and similar to the Large Magellanic Cloud. The EBBA bump may be related to the 2175 A bump seen in the Local Group and may be a counterpart of the 2175 A bump under different conditions in the early Universe. Furthermore, five objects in this sample show low-ionization broad absorption lines (LoBALs), such as Mg II and Al III, in addition to the high-ionization broad absorption lines (HiBALs) of C IV and Si IV. The fraction of LoBALs in our sample, ~70%, is surprisingly high compared to that of general BAL quasars, ~10%. Although the origin of the bump is still not clear, the coexistence of both BALs and bumps and the significantly high fraction of LoBALs may indicate the bump carriers is closely related to the early evolution phase of quasars.Comment: 14 pages, 4 Tables, 9 figures, Submit to The Ap

Unprecedented generation of 3D heterostructures by mechanochemical disassembly and re-ordering of incommensurate metal chalcogenides

Three-dimensional heterostructures are usually created either by assembling two-dimensional building blocks into hierarchical architectures or using stepwise chemical processes that sequentially deposit individual monolayers. Both approaches suffer from a number of issues, including lack of suitable precursors, limited reproducibility, and poor scalability of the preparation protocols. Therefore, development of alternative methods that enable preparation of heterostructured materials is desired. We create heterostructures with incommensurate arrangements of well-defined building blocks using a synthetic approach that comprises mechanical disassembly and simultaneous reordering of layered transition-metal dichalcogenides, MX2, and non-layered monochalcogenides, REX, where M = Ta, Nb, RE = Sm, La, and X = S, Se. We show that the discovered solid-state processes are rooted in stochastic mechanochemical transformations directed by electronic interaction between chemically and structurally dissimilar solids toward atomic-scale ordering, and offer an alternative to conventional heterostructuring. Details of composition–structure–properties relationships in the studied materials are also highlighted

Combining PSR theory with distributional reinforcement learning

This work focuses on using Distributional Reinforcement Learning (DRL) in a partially observable environment that is modelled via Predictive State Representation Theory (PSR). We aim to integrate the benefits of DRL and PSR to obtain a model-based reinforcement learning method that is capable of providing complete (distributional) performance information about a policy using an observation-only environment model. PSR theory is one of the advanced techniques used to model a dynamical system on a partially observable environment. Unlike traditional partially observable Markov models, such as POMDP, which capture the uncertainty of the environment using belief states, PSR model describes the partially observable environment based on probabilities of executable and observable future events. Distributional Reinforcement Learning (DRL), proposed by MG Bellemare, is a learning paradigm that aims to improve learning by modelling the rewards as probability distributions instead of scalar expectations.Master of Engineerin

A Bi-level Globalization Strategy for Non-convex Consensus ADMM and ALADIN

In this paper, we formally analyze global convergence in the realm of distributed consensus optimization. Current solutions have explored such analysis, particularly focusing on consensus alternating direction method of multipliers (CADMM), including convex and non-convex cases. While such efforts on non-convexity offer elegant theory guaranteeing global convergence, they entail strong assumptions and complicated proof techniques that are increasingly pose challenges when adopted to real-world applications. To resolve such tension, we propose a novel bi-level globalization strategy that not only guarantees global convergence but also provides succinct proofs, all while requiring mild assumptions. We begin by adopting such a strategy to perform global convergence analysis for the non-convex cases in C-ADMM. Then, we employ our proposed strategy in consensus augmented Lagrangian based alternating direction inexact Newton method (C-ALADIN), a more recent and generalization of C-ADMM. Surprisingly, our analysis shows that C-ALADIN globally converges to local optimizer, complementary to the prior work on C-ALADIN, which had primarily focused on analyzing local convergence for non-convex cases

Diosgenin Exerts Antitumor Activity via Downregulation of Skp2 in Breast Cancer Cells

Background. Breast cancer is the common malignancy with high morbidity and mortality in women. S-phase kinase-associated protein 2 (Skp2) has been characterized to play an oncogenic role in the breast carcinogenesis and progression. Therefore, inactivation of Skp2 in breast cancer might be a novel approach for fighting breast malignancy. A natural compound diosgenin has been reported to exert anticancer activity in a variety of human cancers. However, the underlying mechanism has not been fully determined. Methods. In this study, we aim to explore whether diosgenin performed antitumor activity via inhibition of Skp2 in breast cancer cells using several methods including MTT, Transwell invasion assay, RT-PCR, western blotting, and transfection. Results. We found that diosgenin inhibited cell viability and stimulated apoptosis. Moreover, we found that diosgenin reduced cell invasion in breast cancer cells. Furthermore, diosgenin inhibited the expression of Skp2 in breast cancer cells. Notably, diosgenin reduced cell viability and motility and induced apoptosis via suppression of Skp2 in breast cancer cells. Conclusion. Our findings revealed that diosgenin could be a potential inhibitor of Skp2 for treating breast cancer

Bladder entrance of microplastic likely induces toxic effects in carnivorous macrophyteUtricularia aureaLour

The global distribution of microplastic (particle size < 5 mm) is of growing concern, especially in aquatic environments where it may cause adverse effects on resident organisms. To date, however, few studies have focused on the impacts of microplastic on aquatic plants. Here, we conducted a microcosm study to investigate the toxic effects of microplastic on the carnivorous aquatic macrophyteUtricularia aureaLour. Based on microscopic images and Raman spectrum analysis, we found that most polyvinyl chloride (PVC) particles were smaller than the valve ofU. aureabladders, thus allowing entrance into the plant, but this was not so for polyethylene (PE) particles. Furthermore, PVC (50 mg L-1) had significantly negative effects on growth and physiological parameters such as macrophyte length, chlorophyll content, and fluorescence, whereas, at the same concentration, PE had no such effects. Further analysis revealed that after bladder removal, the macrophytes did not respond to PVC particle toxicity. Thus, intake of microplastics (i.e., PVC) through bladders is likely responsible for inducing toxic effects to the growth and physiological parameters ofU. aurea