Polymer flooding secondary

The state of the art in chemical oil recovery has been reviewed [1732]. More than two thirds of the original oil remains unrecovered in an oil reservoir after primary and secondary recovery methods have been exhausted. Many chemically based oil-recovery methods have been proposed and tested in the laboratory and field. Indeed, chemical oil-recovery methods offer a real challenge in view of their success in the laboratory and lack of success in the field. The problem lies in the inadequacy of laboratory experiments and the limited knowledge of reservoir characteristics. Field test performances of polymer, alkaline, and micellar flooding methods have been examined for nearly 50 field tests. The oil-recovery performance of micellar floods is the highest, followed by polymer floods. Alkaline floods have been largely unsuccessful. The reasons underlying success or failure are examined in the literature [1732]. 

Sherborne et al. (1967) observed a 15% redaction in residnal oil satnration in a HPAM flood. Wreath (1989) did not observe rednction in residnal oil satnration in tertiary polymer flooding in Berea and Antolini sandstones. Wreath (1989) did not observe rednction in residnal oil satnration in one Berea core even in secondary polymer flood mode, bnt did observe rednction in one Antolini core that was a heterogeneons and eolian sandstone. For more discnssion about kj curves in polymer flooding, see Section 5.4.5. 

There are many faults whose cUstribution is complex in Daqing Oilfield SW-II (Wei Jide, 2001 j.The basic well pattern is put into development by Une well pattern in 1964. In 1990, primary infill wells pattern uses two sets of layer system to develop S and PII poor oil layers. Secondary infill wells pattern is used to adjust S and PII thin and poor oil layers and untabulated reservoir in 1998. In 2000, as P15-1-61—7 oil layers and PI 1-4 oil layers have differences in geologic feature, the polymer flooding is only put into development in PII—4 oil layers. So far, there are only some wells of line well pattern is under production in PI5-F61—7 oil layers. And the flood pattern of P I5-F61—7 oil layers is very incomplete. 

Tertiary recovery focuses on the exploitation of wells after primary (natural pressure of the well) and secondary recovery ( use of water and gas under pressure) have been accomplished. - Water-soluble pol nners are used in polymer flooding. The biopolymer - xanthan gum has proven to have high shear-stability and is insensitive to high electrolyte concentrations at high or low pH. 

When this pressure drops, it can be built-up again by water flooding. Unfortunately, after these primary and secondary processes, there still remains up to 70% of the oil adsorbed on the porous clays. Consequently, in recent years, there have been tremendous efforts made to develop tertiary oil recovery processes, namely carbon dioxide injection, steam flooding, surfactant flooding and the use of microemulsions. In this latter technique, illustrated in Fig. 1, the aim is to dissolve the oil into the microemulsion, then to displace this slug with a polymer solution, used for mobility control, and finally to recover the oil by water injection ( 1). 

Taylor and Flood could show that polystyrene-bound phenylselenic acid in the presence of TBHP can catalyze the oxidation of benzylic alcohols to ketones or aldehydes in a biphasic system (polymer-TBHP/alcohol in CCI4) in good yields (69-100%) (Scheme 117) °. No overoxidation of aldehydes to carboxylic acids was observed and unactivated allylic alcohols or aliphatic alcohols were unreactive under these conditions. In 1999, Berkessel and Sklorz presented a manganese-catalyzed method for the oxidation of primary and secondary alcohols to the corresponding carboxylic acids and ketones (Scheme 118). The authors employed the Mn-tmtacn complex (Mn/168a) in the presence of sodium ascorbate as very efficient cocatalyst and 30% H2O2 as oxidant to oxidize 1-butanol to butyric acid and 2-pentanol to 2-pentanone in yields of 90% and 97%, respectively. This catalytic system shows very good catalytic activity, as can be seen from the fact that for the oxidation of 2-pentanol as little as 0.03% of the catalyst is necessary to obtain the ketone in excellent yield. 

Solubility. Solubility in the primary process solvent is a mandatory criteria which is easily met in most extraction processes conducted in water. But, new applications such as polymeric viscosifiers for supercritical carbon dioxide flooding in enhanced oil recovery present enormous solubility problems for candidate polymers. If the polymer must remain soluble in secondary fluids encountered during the extraction process, then solubility requirements on the polymer will span large ranges of solvent pH, solvent-and-other-solute activity, and solvent polarity. 

Enhanced OO Recovery (EOR). This process refers to the recovery of oil that is left behind after primary and secondary recovery methods have either been exhausted or have become uneconomical. Enhanced oil recovery is the tertiary recovery phase in which surfectant-polymer (SP) flooding is used. SP flooding is similar to waterflooding, but the water is mixed with a surfactant-polymer compound. The surfactant literally cleans the oil off the rock and the polymer spreads the flow through more of the rock. An additional 15 to 25 percent of original oil in place (OOlP) can be recovered. Before this method is used, there is a great deal of evaluation and laboratory testing involved, but it has become a reliable and cost-effective method of oil recovery. 

Secondary recovery (water-flooding), and tertiary recovery using COj micellar fluids and polymers introduce some specific requirements. Inhibitors must have proper solubihty and wetting characteristics and be able to perform in the presence of the surfactants and polymers added to the flood. A surfactant component may be required in the inhibitor to maintain injection rates in produced water... 

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