Experimental Performance Evaluation and Optimization of a Weak Gel Deep-Profile Control System for Sandstone Reservoirs.

Globally, most oil fields use excessive water flooding to recover oil. By injection of water between wells, channels are created, which result in lower oil recovery. Water-plugging deep-profile control must be used to control the excessive water production from an oil reservoir. This laboratory study used sulfonated polyacrylamides with a molecular weight of 10.3-13.0 × 106 Da (FPAM) and polyethylenimine (PEI-600) to formulate a weak gel system to control excessive water production from deep formations. Using different FPAM and PEI-600 concentrations, the Sydansk bottle test approach was applied to evaluate the gelation time, strength, and stability of the weak gel. The weak gel concentration of 0.5 wt % FPAM and 0.4 wt % PEI-600 was confirmed for deep-profile control by this approach. The temperature and salt resistance of the selected weak gel system were evaluated using the same bottle test methodology. The gelation time depends on temperature: 5-7 days at <100 °C to 0.5 days >100 °C. Salinity >20,000 mg/L significantly affected the weak gel system's strength. By performing a viscometer test, the viscosity of the weak gel system at different times was evaluated, confirming the gelation time of the selected weak gel. Next, a microfluidic chip flooding test analyzed weak gel performance and plugging ability in porous media. This micromodel provided a visual analysis of the weak gel plug. Finally, a low- to medium-permeability sandstone core-flooding was conducted to determine the plugging rate of weak gel at the core scale, followed by an evaluation of the injection pressure, blocking effect, and oil recovery. According to the study, the selected weak gel has an extended gelation time with a significantly low viscosity, which affects its injectivity and can move from injection wells into deep formations. In the core-flooding test, the weak gel's blocking rate after 7 days of gelation time exceeded 90%.

Optimization and Performance Evaluation of a Foam Plugging Profile Control Well Selection System.

Most of the oilfields are currently experiencing intermediate to late stages of oil recovery by waterflooding. Channels were created between the wells by water injection and its effect on the oil recovery is less. The use of water plugging profile control is required to control excessive water production from an oil reservoir. First, the well selection for profile control using the fuzzy evaluation method (FEM) and improvement by random forest (RF) classification model is investigated. To identify wells for profile control operation, a fuzzy model with four factors is established; then, a machine learning RF algorithm was applied to create the factor weight with high accuracy decision-making. The data source consists of 18 injection wells, with 70% of the well data being utilized for training and 30% for model testing. Following the fitting of the model, the new factor weight is determined and decisions are made. As a consequence, FEM selects 7 out of 18 wells for profile control, and by using the factor weight developed by RF, 4 out of 18 wells are chosen. Then, the profile control is conducted through a foam system proposed by laboratory experiments. A computer molding group numerical simulation model is created to profile the wells being selected by both methods, FEM and RF. The impact of foam system plugging on daily oil production, water cut, and cumulative oil production of both methods are contrasted. According to the study, the reservoir performed better when four wells were chosen by the weighting system developed by RF as opposed to seven wells that were chosen using the FEM model during the effective period. The weighting model developed by RF accurately increased the profile control wells' decision-making skills.

Determinants of Bezafibrate-induced Improvements in LDL Cholesterol in Dyslipidemic Patients with Diabetes.

AIM: Our previous "J-BENEFIT (Japan BEzafibrate cliNical EFfectIveness and Tolerability)" study demonstrated that bezafibrate improves blood lipid profiles and glucose control in dyslipidemic patients with diabetes. However, bezafibrate did not significantly improve low-density lipoprotein cholesterol (LDL-C), although some patients showed decreases while others showed increases in the LDL-C levels. Therefore, a subgroup analysis of the J-BENEFIT study was conducted to identify factors influencing the bezafibrate-induced changes in the LDL-C levels. METHODS: Of the 3,316 patients in the J-BENEFIT study, 2,116 not treated with other lipid-lowering drugs were enrolled in the current study, and the effects of 24-week treatment with bezafibrate on the LDL-C levels were analyzed. A reduction in the LDL-C level of ≥ 25% occurred in 253 patients, and a logistic-regression analysis was used to identify factors associated with this improvement. RESULTS: Among the 2,116 overall patients, bezafibrate treatment significantly increased the LDL-C levels from 123.9±36.7 to 125.7±31.3 mg/dL. The subanalysis showed that the treatment responses varied according to the baseline LDL-C level, with significant decreases in the ≥ 160 and ≥ 140-＜160 mg/dL groups, no significant decrease in the ≥ 120-＜140 mg/dL group and a significant increase in the ＜120 mg/dL group. A multivariate logistic-regression analysis of the data for the patients with an LDL-C of ≥ 25% identified a female sex, the use of anti-hypertensive and hypoglycemic agents and a high baseline LDL-C level to be significant determinants of the LDL-C response to bezafibrate. CONCLUSIONS: Our results showed that treatment with bezafibrate improves the LDL-C levels and lipid profiles in dyslipidemic diabetic patients, especially women, subjects co-treated with anti-hypertensive or hypoglycemic agents and those with high baseline LDL-C levels.

Safety and efficacy of long-term combination therapy with bezafibrate and ezetimibe in patients with dyslipidemia in the prospective, observational J-COMPATIBLE study.

BACKGROUND: There are numerous reports describing the efficacy of fenofibrate in combination with ezetimibe for treating dyslipidemia. In contrast, a study combining bezafibrate and ezetimibe has not yet been conducted. In this study, we examined the safety, including the risk of gallstone formation, and the efficacy of long-term combination therapy with bezafibrate and ezetimibe for treating dyslipidemia. METHODS: Dyslipidemic patients treated with 400 mg/day bezafibrate in combination with 10 mg/day ezetimibe for the first time were eligible. We selected 157 institutions in Japan and conducted a 12-month prospective observational study, with patients enrolled on the day they started combination therapy. Safety of the combination was examined in terms of the type, onset, and severity of adverse drug reactions (ADRs). Efficacy was evaluated in terms of the changes in low-density lipoprotein-cholesterol (LDL-C), high-density lipoprotein-cholesterol (HDL-C), triglyceride (TG), and non-HDL cholesterol (non-HDL-C) levels from the start of combination therapy (baseline) to the last observation carried forward (LOCF). Lipid levels were assessed at 1, 3, 6, and 12 months after starting combination therapy. RESULTS: We enrolled 665 patients in this observational study. Safety was evaluated in 659, and ADRs occurred in 42 patients (6.4%). The most frequent ADRs were blood creatine phosphokinase increase (1.5%) and myalgia (0.8%). Asymptomatic gallstones were observed in four patients (0.6%). Effectiveness was evaluated in 622 patients. LDL-C, HDL-C, TG, and non-HDL-C levels improved significantly from baseline to LOCF by -17.4%, 8.8%, -40.5%, and -21.6%, respectively (all, p < 0.001). Lipid levels also improved from baseline to each evaluation time-point. CONCLUSIONS: Bezafibrate in combination with ezetimibe is safe and effective, and is potentially useful for comprehensive management of dyslipidemia.