RESUMO
Clean fracturing fluid has the characteristics of being environmentally friendly and causing little damage to reservoirs. Meanwhile, its backflow gel-breaking fluids (GBFs) can be reutilized as an oil displacement agent. This paper systematically evaluates the feasibility and EOR mechanism of a GBF based on a polymer surfactant as an oil displacement system for reutilization. A rotating interfacial tensiometer and contact angle measuring instrument were used to evaluate the performance of reducing the oil-water interfacial tension (IFT) and to change the rock wettability, respectively. Additionally, a homogeneous apparatus was used to prepare emulsions to evaluate GBF's emulsifying properties. Finally, core flooding experiments were used to evaluate the EOR effect of GBFs, and the influence rules and main controlling effects of various properties on the EOR were clarified. As the concentration of GBFs increases, the IFT first decreases to the lowest of 0.37 mN/m at 0.20 wt% and then increases and the contact angle of the rock wall decreases from 129° and stabilizes at 42°. Meanwhile, the emulsion droplet size gradually decreases and stabilizes with increases in GBF concentration, and the smallest particle size occurs when the concentration is 0.12-0.15 wt%. The limited adsorption area of the oil-water interface and the long molecular chain are the main reasons that limit the continued IFT reduction and emulsion stability. The oil displacement experiment shows that the concentration of GBF solution to obtain the best EOR effect is 0.15 wt%. At this concentration, the IFT reduction and the emulsification performance are not optimal. This shows that the IFT reduction performance, reservoir wettability change performance, and emulsification performance jointly determine the EOR effect of GBFs. In contrast, the emulsifying performance of GBFs is the main controlling factor for the EOR. Finally, the optimal application concentration of GBFs is 0.15-0.20 wt%, and the optimal injection volume is 0.5 PV.
RESUMO
Objective: The purpose of the research was to explore the possible risk factors for the development of hypocomplementemia (HC) in rheumatoid arthritis (RA) patients by analyzing their clinical and laboratory features. Methods: This retrospective research contained 501 RA patients, divided into RA patients with HC (n=78) and RA patients without HC (n=423). Demographic characteristics and laboratory test results of RA patients were collected and analyzed, such as age, sex, anti-mutated citrullinated vimentin antibody (Anti-MCV), serum complements (C3, C4), immunoglobulins (IgA, IgG, IgM), hemoglobin (Hb), platelets (PLT) and erythrocyte sedimentation rate (ESR), etc. Spearman correlation was served as assessing the correlations of the levels of serum C3 and C4 with each index. Receiver operating characteristic (ROC) curves were served as assessing the diagnostic efficacy of each index for RA patients with HC. Furthermore, risk factors for the occurrence of HC in RA patients were analyzed by employing binary logistic regression of single and multiple factors. Results: Compared RA patients with HC to without HC, the former were older and had a longer disease duration with increased levels of Anti-MCV, IgM and DAS28 and lower levels of Hb, PLT and ESR; Spearman correlation analysis verified the level of serum Anti-MCV was a negative correlation with C3 (r=-0.156); the area under the ROC curve (AUC) of PLT in diagnosing RA patients with HC was the largest at 0.65 (95% CI: 0.60-0.69); binary logistic regression analysis indicated that advanced age (>66 years), long disease duration (>62 months), high DAS28 value (>6.13), the levels of Anti-MCV>107.68IU/mL, IgM>1.54g/L, ESR≤69.00mm/h, Hb≤99.00g/L and PLT≤305.00×109/L were probable risk factors for the occurrence of HC in RA patients. Conclusion: Age and disease duration, DAS28, Anti-MCV, IgM, ESR, Hb, and PLT are closely related to the development of HC in RA patients. Timely monitoring of these indicators can help to evaluate disease activity of RA patients and further improve their prognosis.
