When flooding with viscous Polymers, due to the increase in viscosity and decrease in permeability (for polymers that absorb on the rock surface), the mobility ratio compared to water flooding becomes more favorable. Therefore the volumetric sweep efficiency increases and the recovery of the reservoir on a macro scale increases also. Most people think that polymer flooding does not increase the recovery at a micro scale. But numerous results in this work do not support this conclusion. From cores in the lab, the effect of flooding with viscous-elastic polymers on different types of residual oil after water flooding was studied. The different types of residual oil are:oil film on the rock surface;oil in "dead ends";oil in pores throats retained by capillary forces;oil un-swept in micro scale heterogeneous portions of the core. It could be seen that all types of micro-scale residual oil were reduced after flooding with viscous-elastic polymers. Due to the elastic nature of the polymer, the velocity distribution in the pores are quite different from Newtonian Fluids and the polymer could also exert a very strong "pulling effect" on different types of residual oil. The study pointed out that the relationship between Capillary Number and Recovery of cores for Newtonian Fluids does not apply to fluids with elastic properties. In the study, it was seen that the increase in micro scale recovery was related to the elastic properties of the polymer fluids. Different polymer fluids had quite different elastic properties. Some had practically no elasticity. Therefore, when selecting polymers for flooding, its elastic properties must be considered. The difference in incremental recovery can be more than 6% OOIP (original oil in place), which is substantial, it can make a polymer flood successful (both technically and economically) or not. The above conclusions can also be confirmed by pressure coring data and field results of large scale polymer (PAM) flooding in Daqing Oil Field, which is obtaining an incremental oil recovery of more than 13% OOIP. This magnitude of incremental oil recovery can not be explained by just an increase in volumetric sweep efficiency. The above conclusionscan explain why some polymer floods were successful or not;should be considered when selecting polymer floods and,should be able to increase the incremental oil of future polymer floods. The rheology of viscous-elastic fluids in porous media is very much different from fluids with no elasticity. Much work needs to be done in this field. Many conclusion obtained by studies on Newtonian Fluids need to be re-assessed when used on visco-elastic fluids. Introduction The relationship between Capillary Number and Recovery when flooding cores with Newtonian Fluids is well-established[1]. It is known that to obtain substantial increase in recovery at a micro scale in cores, the Capillary Number needs to be increased several thousand times, but the increase when flooding with polymers, compared to with water, usually is less than one hundred. Therefore, most people think that polymer flooding does not increase the recovery at a micro scale. However, in the lab, the recovery from natural and artificial consolidated cores were mostly 5~8% OOIP higher when polymer flooded than water flooded. The same results were obtained by flooding glass-etched cores. The end point (oil saturation when water cut reaches 100%) of relative permeability curves were 6~8% lower for polymer flooding than by water flooding. Pressure cores in polymer flooded portions of the reservoir showed residual oil saturation much lower than could be obtained by water flooding.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractResidual oil after water flooding appears in three types: oil drops, films and clusters. Work performed using Newtonian fluids shows that to mobilize the residual oil remaining after water flooding, the driving forces, on condition of oil-water IFT (interfacial tension) being constant, need to be increased by one thousand to ten thousand times over that of waterflooding before the capillary forces retaining the residual oil can be overcome [1] . Viscous forces cannot be increased by such a large magnitude in the field.Polyacrylamide (PAM) solutions have little effect on the oilwater IFT. However, results in the laboratory and field show that after flooding by polymer fluids, all types of microscopic scale residual oil in porous media are lowered [2] . The amount that is lowered is related to the elasticity of the fluids. Other conditions being the same, the higher the elasticity, the lower the residual oil saturation. The results of lab tests (including microscopic visualization cores) show that viscoelastic fluid flooding can lower the residual oil saturation in cores of different wettabilities. The main forces to mobilize the residual oil by viscoelastic fluids are not entirely the same as that of Newtonian fluids. It is not only a force perpendicular to the oil-water interface overcoming the restraining capillary force, but also a viscous dragging force parallel to the oil-water interface that mobilizes the residual oil.

A series of surface active sulfo-propane betaines and sulfo-butane betaines were synthesized with high yields by the reaction of an appropriate N,N-dimethyl alkylamine with an excess of 1,3-propane sultone and 1,4-butane sultone. The structures were characterized by 1 H-NMR spectroscopy and elemental analysis. The micellar properties of these compounds were determined by surface tension methods. Surface tension measurements also provide information about the dependence of the surface tension at the CMC (c cmc ), pC 20 (negative logarithm of the surfactant molar concentration C 20 required to reduce the surface tension by 20 mN/m), the surface excess (C max ) at air/solution interface, the minimum area per surfactant molecule at the air solution interface (A).

Pilot tests commenced from 1980s in Daqing Oilfield have proved that ASP flooding could improve the recovery rate by 20% based on water flooding, while scaling issue in producers was the only factor which made it hard to reach that objective. Investigation in site indicated that more than 70 percent producers had scaling issues, and scaling types and degree in ASP producers varied dramatically in different wells and different period. In the peak of scaling period, the averaged running life was only a couple of months. A project focused on the harness of scaling issue in ASP producers was implemented from 2002. In the first stage, the study aimed at getting the scaling principle in ASP producers. A series of monitoring and analysis on producing fluid's ion concentration were implemented in different ASP producers. The scale deposited on tubing in different depths were picked out and analyzed. The scaling mechanism of ASP producing liquids in artificial lift systems were created which presented the varying principle of scaling ions as well as the characteristics of scale in ASP producers. A set of scaling principle prediction plates was also created with a success ratio being above 90%. In the second stage, a series of anti-scaling artificial lift techniques were developed including new anti-scaling pump, chemical scale removers and scale inhibitors, and other matching techniques. The new anti-scaling techniques were put into application from several wells up to near 1,000 wells. The operating rate has been improved by 4.13 percent as well as the operating cost decreased by 72.77%. The technical breakthrough in anti-scaling artificial lift systems improved the operating life of ASP producers considerably. It applied solid foundation for ASP flooding to become a beneficial method for mature oilfield development in commercial scale.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractResidual oil after water flooding appears in three types: oil drops, films and clusters. Work performed using Newtonian fluids shows that to mobilize the residual oil remaining after water flooding, the driving forces, on condition of oil-water IFT (interfacial tension) being constant, need to be increased by one thousand to ten thousand times over that of waterflooding before the capillary forces retaining the residual oil can be overcome [1] . Viscous forces cannot be increased by such a large magnitude in the field.Polyacrylamide (PAM) solutions have little effect on the oilwater IFT. However, results in the laboratory and field show that after flooding by polymer fluids, all types of microscopic scale residual oil in porous media are lowered [2] . The amount that is lowered is related to the elasticity of the fluids. Other conditions being the same, the higher the elasticity, the lower the residual oil saturation. The results of lab tests (including microscopic visualization cores) show that viscoelastic fluid flooding can lower the residual oil saturation in cores of different wettabilities. The main forces to mobilize the residual oil by viscoelastic fluids are not entirely the same as that of Newtonian fluids. It is not only a force perpendicular to the oil-water interface overcoming the restraining capillary force, but also a viscous dragging force parallel to the oil-water interface that mobilizes the residual oil.