TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractWithin the past 40 years, profile modification has been widely used in China to control excess water production and improve waterflood sweep efficiency. As most reservoirs reach mature stage, single well treatment often becomes uneconomic. Therefore, profile modification treatments of multiple injectors based on reservoir scale have been applied to improve reservoir conformance. In this paper, a method is introduced to optimize the design of the treatment. The selection of the wells and target layers, as well as the chemical agent and injection parameters can be achieved by this method. The selection of candidate wells is based on fuzzy mathematics methods, considering well injectivity, reservoir heterogeneity and offset production well performance. The chemical agent is selected from over 40 formula commonly used in China, according to its compatibility with reservoir characteristics and well injectivity. The volume of treatment is optimized by running numerical simulations. This optimization method has been widely used in many oilfields in China. In most cases, production analysis after treatment shows that the waterflood efficiency is improved, and that the model predictions match well with the actual production data. As an example, a detailed analysis of the treatment performed in the Long 11 fault-block reservoir in Qing Long Tai oilfield is given in the paper.
Thioredoxins are oxidoreductases that help to maintain redox homeostasis in plants under abiotic stress. In this study, a new thioredoxin gene, SikTrxh, was cloned from Saussurea involucrata (Kar. & Kir.), a perennial herb that grows in the high alpine mountains of Central Asia. Bioinformatics analysis shows that the full-length cDNA of SikTrxh consisted of 565 bp with a 354-bp open reading frame and encoded a 117 amino acid protein. Using quantitative reverse transcription (RT) PCR, we found that the expression of the SikTrxh gene was induced by salt, cold, and drought stresses, suggesting that this protein played a significant role in plant defense. Subcellular localization confirmed that the protein was localized to the mitochondria. A vector carrying SikTrxh was inserted into tobacco, and successfully modified plants were identified by RT-PCR. Physiological indicators and antioxidant enzyme activities were measured under low temperature, and salt and drought stresses. Our results show that malondialdehyde content and relative electrolyte leakage increased in both wild-type and SikTrxh-overexpressing transgenic plants; however, these increases were significantly higher in the wild-type plants than in the transgenic plants. We also found that photosystem II photoinhibition was lower in the transgenic plants than in the wild-type plants, and that activities of reactive oxygen species-scavenging enzymes were higher in the transgenic plants than in the wild-type plants. We conclude that SikTrxh can reduce toxic effects of reactive oxygen species to protect the plasma membrane, thereby increasing plant resistance to abiotic stresses.
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