Enhanced Tertiary Oil Recovery

Displacement of oil in petroleum reservoirs by water or chemical flooding (five-spot pattern) 

Brine Formation water or water from sea, lakes, and rivers with variable saline conditions and concentrations (mg/L to g/L) 

Chemicals Primary surfactant (e.g., petroleum sulfonate) Co-surfactant/co-solvent (e.g., C3 to C5 alcohol) Polymer (e.g., xanthan) Alkaline agents (e.g., sodium carbonate) Bactericides (e.g., formaldehyde) Sacrificial adsorption agents 

Good solubility in the brine at surface and reservoir conditions 

Good thermal stability under reservoir conditions 

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One of the major focuses of the in situ use of surfactants is to accelerate the removal or degradation of free-phase products (DNAPL or oil globules) as variations of technologies used in the oil industry for enhanced tertiary oil recovery as described by Hill et al. (1973)- Such in situ remediation efforts often fail, however, primarily because of differences in the goals and expectations of the applications. For example, the enhanced oil recovery industry is often satisfied with > 30% enhanced removal whereas the remediation industry often strives for >99% removal in order to meet remedial guidelines. Unfortunately, removal of about 50% of the free product (i.e., DNAPL) at a PAH-contaminated site appears to represent the full extent of practical field expectations. 

Microemulsions are potentially exploitable in any situation where the mixing of oil and water is desired. The possibility of using them to enhance tertiary oil recovery has recently attracted a great deal of attention. 

In primary oil recovery from underground reservoirs, the capillary forces described by the Young and Young-Laplace equations are responsible for retaining much of the oil (residual oil) in parts of the pore structure in the rock or sand. It is these same forces that any secondary or enhanced (tertiary) oil-recovery-process strategies are intended to overcome [2,133,421,690,691]. In an oil-bearing reservoir the relative oil and water saturations depend upon the distribution of pore sizes in the rock. The capillary pressure in a pore is... 

Surfactant aggregates (microemulsions, micelles, monolayers, vesicles, and liquid crystals) are recently the subject of extensive basic and applied research, because of their inherently interesting chemistry, as well as their diverse technical applications in such fields as petroleum, agriculture, pharmaceuticals, and detergents. Some of the important systems which these aggregates may model are enzyme catalysis, membrane transport, and drug delivery. More practical uses for them are enhanced tertiary oil recovery, emulsion polymerization, and solubilization and detoxification of pesticides and other toxic organic chemicals. 

Applications in Oil and Gas Production. AMP is useful for removing CO2 from gaseous mixtures (23). It also has been utilized in tertiary oil recovery to enhance removal of petroleum from marginal wells (24). 

The possible strnctnres which can be formed by a mixtnre of hydrocarbon oil, surfactant and water is illnstrated below in Fignre 5.2. The variation and complexity of these strnctnres has led to mnch research on potential indnstrial applications from tertiary oil recovery to enhanced drng delivery systems. Many of the strnctnres can be predicted using models based on the optimal cnrvatnre of the interface, not nnlike that nsed to predict snrfactant aggregation. 

Multicomponent phase ecjuilibria involving three or more coexisting fluid phases is frequently encountered in liquefied natural gas processes (1), tertiary oil recovery by miscible gas displacement (2), and the use of surfactants in enhanced oil recovery (3). 

Enhanced Oil Recovery The third phase of crude-oil production, in which chemical, miscible fluid, or thermal methods are applied to restore production from a depleted reservoir. Also known as tertiary oil recovery. See also Primary Oil Recovery, Secondary Oil Recovery. 

We have recently reported (6, 7) that those surfactant formulations which yield good oil recovery exhibit both low interfacial tensions and low interfacial viscosities. Our experiments have shown that surfactant formulations which ensure low interfacial viscosity will promote the coalescence of oil droplets and thereby decrease the emulsion stability, thus enhancing the formation of a continuous oil bank. It has been demonstrated that the requirements for emulsion stability are the presence of an interfacial film of high viscosity and a film of considerable thickness. We have observed that the surfactant concentration which minimizes the interfacial tension may not simultaneously minimize the interfacial viscosity. Hence, our results indicate both interfacial tension and interfacial rheology must be considered in selecting surfactant formulations for tertiary oil recovery. 

Several alkaline chemicals have been employed for various aspects of enhanced oil recovery. Two of the most favorable alkaline chemicals tested and used in tertiary oil recovery are sodium orthosilicate and sodium hydroxide. Comparing their characteristics, both chemicals react with acids in crude oil to form surfactants, precipitate hardness ions and change rock surface wettability. One difference between the two chemicals is that the interfacial properties for sodium orthosilicate systems are less affected by hardness ions (13), hence slightly lower interfacial tensions would occur. Lower Interfacial tensions can aid in in-situ emulsion formation. 

S Vijayan, C Ramachandran, H Doshi, DO Shah. Porous media rheology of emulsions in tertiary oil recovery. S)un-posium of Surface Phenomena in Enhanced Oil Recovery. Third International Conference on Surface and Colloid Science, Stockholm, 1979, p 327. 

Ball, J.T., and Pitts, M.J. "Effect of Varying Polyacrylamide Molecular Weight on Tertiary Oil Recovery from Porous Media of Varying Permeability," paper SPE 12650 presented at the SPE/DOE 4th Symp. on Enhanced Oil Recovery, Tulsa, Oklahoma, April 1982. 

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