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To evaluate the effect of stratified water injection accurately during different development stages, a Lorenz-curve model was constructed upon a modified four-parameter Sarabia-Lorenz-curve model with water injectivity test data over years, and the relationship between accumulative perforated sandstone thickness and injected water volume of single wells was described by the model. Three evaluation indexes, dimensionless water injectivity intensity, vertical sweep efficiency and water-injection non-balanced degree, and their calculation were presented. Dimensionless water injectivity intensity is used to evaluate the distribution and balanced degree of water injectivity intensity, vertical sweep efficiency is the proportion of oil layers that produce oil, and water-injection non-balanced degree illustrates the overall water-injection balanced condition, then the model is solved by particle swarm optimization algorithm. Thirty-eight stratified water injection wells were evaluated in the Daqing Xingshugang oilfield. And the factors influencing the effect of water injection in single wells were studied considering segments construction, water allocation projects and reservoir physical properties. Finally, technological limits of stratified water injection were proposed under extreme high water-cut and recovery. Key words: stratified water injection, Lorenz-curve model, dimensionless water injectivity intensity, water-injection non-balanced degree, vertical sweep efficiency, technological limits of layering

Developing cost-effective and simple analysis tools is of vital importance for practical applications in bioanalysis. In this work, a new disposable electrochemical cell sensor with low cost and simple fabrication was proposed to study the electrochemical behavior of leukemia K562 cells and the effect of anticancer drugs on cell viability. The analytical device was integrated by using ITO glass as the substrate of working electrodes and paper as the electrolytic cell. The cyclic voltammetry of the K562 cells at the disposable electrode exhibited an irreversible anodic peak and the peak current is proportional to the cell number. This anodic peak is attributed to the oxidation of guanine in cells involving two protons per transfer of two electrons. For the drug sensitivity tests, arsenic trioxide and cyclophosphamide were added to cell culture media. As a result, the electrochemical responses of the K562 cells decreased significantly. The cytotoxicity curves and results obtained corresponded well with the results of CCK-8 assays. In comparison to conventional methods, the proposed method is simple, rapid and inexpensive. More importantly, the developed sensor is supposed to be a single-use disposable device and electrodes were prepared "as new" for each experiment. We think that such disposable electrodes with these characteristics are suitable for experimental study with cancer cells or other types of pathogens for disease diagnosis, drug selection and on-site monitoring.