Abstract Ferrous iron (Fe2+) is one of the most common cations existing in oil and gas production water. Most Fe2+ ions come from dissolution of siderite in reservoir and corrosion of steel pipes. Compared to Ca2+ and Mg2+, Fe2+ has a higher complex stability constant with some common inhibitor function groups like phosphonate and carboxyl due to its transition metal structure. Therefore, understanding the influence of Fe2+ on inhibitors is important to enhance inhibition performance. Work still remain to be done to understand the effect of Fe2+ on scale inhibition, including a systematic study of the Fe2+ influence on phosphonate and polymeric scale inhibitors at different pH, values and molar ratios. Little research has been done at temperatures above room temperature, probably due to the difficulty of developing strictly anoxic test apparatus. In this study, a new anoxic laser apparatus is designed to test inhibitor performance. This newly designed apparatus features constant Argon gas headspace purging during an experiment to guarantee a strict maintenance of anoxic condition. This anoxic apparatus is based on laser detection method of nucleation induction time. It is easy to operate and enables experiments to be conducted at temperatures up to 200°F.
Abstract In the medium/high permeability sandstone reservoirs, long-term water flooding led to large pore channels formed in the reservoir, and the injected water quickly breaks into oil wells along the large pore channels, resulting in water cut increase rapidly and a significant reduction in water flooding efficiency. The traditional water shut-off by chemical or cement squeeze cannot reduce water cut for a long time and cannot increase oil production because they don't change the existing seepage characteristics of the reservoir. The seepage reconstruction is a combination of chemical water shut-off and fracturing technology. It involves innovation on intelligent water control materials and fracturing injection process. There are three plugging slugs, a strong plugging slug, a seepage reconstruction slug, and a tail plugging slug, should be filled into reservoir one by one. The strong plugging slug adopts inorganic polymer to shut-off the large pore by low speed injection. The seepage reconstruction slug is composed of 70-140 mesh quartz sand, 50-80um ceramist and intelligent water control materials with a ratio of 6:3:1, which is carried by low-concentration guar. The tail plugging slug is made of self-consolidated material to prevent sand returning from formation. The technology is used in G111-6 located in J oil field, which is successful in increasing oil production from 3.08bopd to 56.28bopd and reducing the water cut from 96.64% to 78%. The validity period was 492d, and the total oil production was 22624bbls. The technology of seepage reconstruction for water shut-off could effectively reduce the water cut and greatly increase the daily oil production. It effectively improves waterflood development efficiency of medium/high permeability sandstone reservoirs in high water cut stage. The innovation of this technology is the effective combination of fracturing technology and traditional chemical water shut off technology. The goals of water shut-off and oil increase are realized by innovative design of three plugging slugs. It provides a new approach for water shut-off in medium/high permeability sandstone reservoirs with high water cut.
Background: The independent prognostic factors for survival of patients with bone metastatic prostate cancer (PCa) remain controversial; Besides, a nomogram for application to multiple ethnicities has yet to be established. We aimed to build a generic nomogram to predict the prognosis of bone metastatic PCa.Methods: The independent prognostic factors for survival were identified, and the nomogram was further developed in a retrospective study of 1,556 patients with bone metastatic PCa registered in the Surveillance, Epidemiology and End Results (SEER) database. The discriminative ability of the nomogram was assessed by C-index (concordance index) and ROC (receiver operating characteristic) curve analysis, whereas its predictive accuracy was measured by calibration curve assessment. Furthermore, the model was externally validated using the data of 711 patients enrolled in the same database at different times.Results: Age ≥70 years, Gleason score ≥8, stage T4, stage N1, liver metastases, and Asian/Pacific ethnicity were identified as independent prognostic factors. The C-index of the nomogram for predicting cancer-specific survival (CSS) was 0.68 (95% confidence interval [CI]: 0.65-0.70), with areas under the receiver operating characteristic (ROC) curve (AUCs) for one, three, and five years of 0.70, 0.70, and 0.76, respectively. In the validation cohort, the C-index was 0.66 (95% CI: 0.62 to 0.69), with AUCs for one, three, and five years of 0.67, 0.66 and 0.71, respectively. The calibration curve presented a strong agreement between the nomogram-predicted and actual one-, three-, and five-year CSSs in both the primary and external validation cohorts.Conclusion: We established and validated the first nomogram applied to multiple races for predicting the one-, three-, and five-year CSSs of patients with bone metastatic PCa, which will further facilitate individualized clinical decision-making and will be useful for patient counseling.Funding: This study is supported by the Key Science and Technology Program of Shaanxi Province, PR China (grant number: 2016SF-162) and the Development Funds of Shaanxi Science and Technology Agency of China (grant number:2018SF/091).Declaration of Interest: There are no conflicts of interest.Ethical Approval: The present study conformed to the 1964 Helsinki Declaration and its later amendments and was performed under the ethical standards of the institutional and national research committees.
This minireview explores the unique properties and potential applications of bismuth oxychalcogenide nanosheets in chemical and biological sensing, and photodetection.
Calcite and barite are two of the most common scale minerals that occur in various geochemical and industrial processes. Their solubility predictions at extreme conditions (e.g., up to 250 °C and 1500 bar) in the presence of mixed electrolytes are hindered by the lack of experimental data and thermodynamic model. In this study, calcite solubility in the presence of high Na2SO4 (i.e., 0.0407 m Na2SO4) and barite solubility in a synthetic brine at up to 250 °C and 1500 bar were measured using our high-temperature high-pressure geothermal apparatus. Using this set of experimental data and other thermodynamic data from a thorough literature review, a comprehensive thermodynamic model was developed based on the Pitzer theory. In order to generate a set of Pitzer theory virial coefficients with reliable temperature and pressure dependencies which are applicable to a typical water system (i.e., Na-K-Mg-Ca-Ba-Sr-Cl-SO4-CO3-HCO3-CO2-H2O) that may occur in geochemical and industrial processes, we simultaneously fit all available mineral solubility, CO2 solubility, as well as solution density. With this model, calcite and barite solubilities can be accurately predicted under such extreme conditions in the presence of mixed electrolytes. Furthermore, the 95% confidence intervals of the estimation errors for solution density predictions are within 4 × 10–4 g/cm3. The relative errors of CO2 solubility prediction are within 0.75%. The estimation errors of the saturation index mean values for gypsum, anhydrite, and celestite are within ±0.1 and that for halite is within ±0.01, most of which are within experimental uncertainties.
Two-dimensional (2D) molybdenum ditelluride (MoTe2) is an interesting material for fundamental study and applications, due to its ability to exist in different polymorphs of 2H, 1T, and 1T', their phase change behavior, and unique electronic properties. Although much progress has been made in the growth of high-quality flakes and films of 2H and 1T'-MoTe2 phases, phase-selective growth of all three phases remains a huge challenge, due to the lack of enough information on their growth mechanism. Herein, we present a novel approach to growing films and geometrical-shaped few-layer flakes of 2D 2H-, 1T-, and 1T'-MoTe2 by atmospheric-pressure chemical vapor deposition (APCVD) and present a thorough understanding of the phase-selective growth mechanism by employing the concept of thermodynamics and chemical kinetics involved in the growth processes. Our approach involves optimization of growth parameters and understanding using thermodynamical software, HSC Chemistry. A lattice strain-mediated mechanism has been proposed to explain the phase selective growth of 2D MoTe2, and different chemical kinetics-guided strategies have been developed to grow MoTe2 flakes and films.
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