Polymer flooding tertiary

Malmberg, E.W. Smith, L. The Adsorption Losses of Surfactants in Tertiary Recovery Systems in Porous Media in Improved Oil Recovery by Surfactant and Polymer Flooding, Shah, D.O. Schechter, R.S. (Eds.), Academic Press New York, 1977, pp. 275-292. 

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. 

Sun, H.-Q., 2005. Formula selection and pilot test of a surfactant-polymer flooding. In Yan, C.-Z., Li, Y. (Eds.), Tertiary Oil Recovery Symposium. Petroleum Industry Press, pp. 116-122. 

Yang, P.-H., et al., 1992. Oil recovery mechanisms of alkaline/polymer flooding. Paper presented at the Second and Tertiary Recovery Symposium, Chengdu. 

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). 

Entrapment and mobilization mechanisms at low flow rates and low interfacial tension can also control the recovery obtained by tertiary methods. In micellar flooding, for example, high ratios of viscous to capillary forces arise at field flow rates when interfacial tensions are very low. Development of a continuous oil bank having significant mobility requires that discontinuous oil be mobilized to form a continuous bank which gathers more residual oil as it advances. Interfacial tensions may exist or develop between the micellar bank and the oil, or between the micellar fluid and the aqueous polymer bank used to push the micellar fluid. Entrapment of oil by the micellar bank, or of micellar fluid by the polymer bank would eventually cause the process to fail. 

Maximal oil recovery still occurred at 1.5% NaCl polymer solution. The interfacial tension between effluent oil and brine (or microemulsion) remains approximately the same (for both sand packs at a given salinity) as shown in Figure 3. The pressure drop history during tertiary flooding also shows nearly identical behavior for long and short sand packs. These observations indicate that the transport process in porous media is nearly the same for the 1.1 and 4 ft long sand packs and the conclusions drawn in section 1 should also be valid for oil displacement in 4 ft long sand packs. 

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. 

During the mid-1970 s, Conoco Inc. completed a successful tertiary recovery pilot flood in the Second Wall Creek sand of the Big Muddy field, located near Glenrock, WY. A sodium sulfonate surfactant was used to lower the interfacial tension between the crude oil and the reservoir brine, while a polysaccharide polymer was used to reduce the mobility of the injected fluids. 

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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