Total syntheses of multidrug resistant inhibitors (-)-acetylardeemin 2a, (-)-ardeemin 2b, and (-)-formylardeemin 3 have been achieved within 10 steps starting from bromopyrroloinoline 13. The key step involves direct alkylation of 13 with prenyl tributylstannane 11 to yield 12 via a silver-promoted asymmetric Friedel-Crafts reaction. Highly efficient installation of the isoprenyl group allowed excellent overall yield. Moreover, the substrate scope of the asymmetric Friedel-Crafts reaction of 13 was expanded to include a variety of arenes 14 to afford natural product-like library analogues 15.
Early in 1964, Pye and Sandiford established the fact that polymer flooding can result in greater oil recovery than the conventional water flooding. Many additional papers sustaining and extending this information have since appeared in the literature. In the past forty years, many field-scale polymer flooding projects have been put into production and lots of information has been available from which to draw conclusions regarding of lessons learnt and experiences gained on field-scale polymer-flooding. The purpose of this paper is to examine the ranges of some important parameters within which successful polymer flooding has been achieved and to present lessons learnt and best practices on polymer flooding, thus direct to design and further achieve a high-performance polymer-flooding project.
Introduction
Mechanisms of Polymer Flooding
In the reservoir, oil and water are immiscible fluids. As a result, neither one can completely displace the other in the subsurface condition. This is reflected by the non-zero irreducible water (Swir) and residual oil saturation (Sor) on an oil-water relative-permeability curve. In the lab, no matter how large volume of water has been injected into a core, the oil saturation will never be lower than Sor only by the conventional water flooding.
However, it has been known for many years that the efficiency of a water flooding can be greatly improved by lowering the water-oil mobility ratio in the system. Such a change may lead to better sweep efficiency and also to more efficient oil displacement in the swept zone. By adding of suitable polymer solutions to injected water, the water mobility can be reduced and oil recovery increased as shown in Figure 1.
During polymer flooding, a water-soluble polymer is added to the injected water in order to increase water viscosity. Depending on the type of polymer used, the effective permeability to water can be reduced in the swept zones to different degrees. It is believed that polymer flooding cannot reduce the Sor, but it is still an efficient way to reach the Sor more quickly or/and more economically.
According to Riley B. Needham[2], polymer solutions may lead to an increase in oil recovery over that from a conventional water flooding by three potential ways:through the effects of polymers on fractional flow,by decreasing the water/oil mobility ratio, andby diverting the injected water from zones that have been swept.
The above three effects can make the polymer flooding process more efficient.
Early pilot studies on polymer flooding can be traced back to 1944. Detling[3] (Shell Development Co.) obtained a U.S. patent covering the use of several additives for viscous water flooding. His objective was to increase the viscosity of the flooding water and then to improve water-oil mobility ratios. During the next two decades, many studies[4–13] have shown up like mushrooms and many patents have been granted covering specific water-soluble polymers or specific conditions of viscous water flooding in the world.
Four new α-pyrones (1-4) and eight known analogues (5-12) were identified from the secondary metabolites of Streptomyces sp. OUCMDZ-3436 derived from the marine green algae Enteromorpha prolifera. Seven new α-pyridones (14-20) were constructed by diversity-oriented synthesis, which has been an effective approach to expanding the chemical space of natural-product-like compounds. Compounds 16, 17, 19, and 20 were found to have inhibitory effect on the gene expression controlled by quorum sensing in Pseudomonas aeruginosa QSIS-lasI.
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