Flooding miscible

Most CO2 miscible EOR projects are located in the west Texas Permian Basin where as much as two-thirds of the oil remains after waterflooding. An incremental (10%) recovery is typical for Permian Basin CO2 floods, which could correspond to as much as 0.5 x 10 (3-4 x 10 bbl) (23). 

Surfactants for Mobility Control. Water, which can have a mobihty up to 10 times that of oil, has been used to decrease the mobihty of gases and supercritical CO2 (mobihty on the order of 50 times that of oil) used in miscible flooding. Gas oil mobihty ratios, Af, can be calculated by the following (22) ... 

The choice of a specific CO2 removal system depends on the overall ammonia plant design and process integration. Important considerations include CO2 sHp required, CO2 partial pressure in the synthesis gas, presence or lack of sulfur, process energy demands, investment cost, availabiUty of solvent, and CO2 recovery requirements. Carbon dioxide is normally recovered for use in the manufacture of urea, in the carbonated beverage industry, or for enhanced oil recovery by miscible flooding. 

The three classes of EOR technologies that have been studied extensively are thermal recovery, miscible flooding, and chemical flooding. For each of these methods, the following two basic problems must be overcome if we are to recover a significant part of the remaining oil. 

Another EOR approach to reducing the viscosity of oil in the reservoir is ntiscible flooding— the injection of fluids that mix with the oil under reservoir conditions. Such fluids include carbon dioxide, light hydrocarbons, and ititrogen. Supply and cost of carbon dioxide are often more favorable than for other injectants. Extensive research and field testing have established the techiucal viability of miscible flooding, and a nnmber of commercial carbon dioxide miscible flooding projects are in operation. 

Enhanced oil-recovery processes include chemical and gas floods, steam, combustion, and electric heating. Gas floods, including immiscible and miscible processes, are usually defined by injected fluids (carbon dioxide, flue gas, nitrogen, or hydrocarbon). Steam projects involve cyclic steam (huff and puff) or steam drive. Combustion technologies can be subdivided into those that autoignite and those that require a heat source at injectors [521]. 

Micellar flooding is a promising tertiary oil-recovery method, perhaps the only method that has been shown to be successful in the field for depleted light oil reservoirs. As a tertiary recovery method, the micellar flooding process has desirable features of several chemical methods (e.g., miscible-type displacement) and is less susceptible to some of the drawbacks of chemical methods, such as adsorption. It has been shown that a suitable preflush can considerably curtail the surfactant loss to the rock matrix. In addition, the use of multiple micellar solutions, selected on the basis of phase behavior, can increase oil recovery with respect to the amount of surfactant, in comparison with a single solution. Laboratory tests showed that oil recovery-to-slug volume ratios as high as 15 can be achieved [439]. 

Despite its relatively high mobility, water has been used to decrease the mobility of even higher mobility gases and supercritical CO used in miscible flooding (361). While water mobility can be up to ten times that of oil, the mobility of gases can be 50 times that of oil (362). The following formula is used to calculate gas oil mobility ratios (363) ... 

Miscible-Flood Enhanced Oil Recovery, ACS Symposium Series No. 373, American Chemical Society, Washington, D.C., 1988. 

Surface Behavior. Most extraction processes deal with several phases. At the boundaries between these phases, an interface exists which can be populated with or depopulated of polymer. Situations in which the polymer should accumulate at the surface of one phase are 1. the flocculation of clays and fines or 2. the formation of foams, while situations in which the polymer should depopulate the surface of the phase boundary are 3 minimizing adsorption in mineral acid leaching or 4. minimizing surface tension with surfactants in oil recovery by miscible flooding.,... 

Petroleum recovery typically deals with conjugate fluid phases, that is, with two or more fluids that are in thermodynamic equilibrium. Conjugate phases are also encountered when amphiphiles fe.g.. surfactants or alcohols) are used in enhanced oil recovery, whether the amphiphiles are added to lower interfacial tensions, or to create dispersions to improve mobility control in miscible flooding 11.21. 

In an earlier study calorimetry achieved this objective for the compositional boundaries between two and three phases (2). Such boundaries are encountered both in "middle-phase microemulsion systems" of low tension flooding, and as the "gas, oil, and water" of multi-contact miscible EOR systems (LZ). The three-phase problem presents by far the most severe experimental and interpretational difficulties. Hence, the earlier results have encouraged us to continue the development of calorimetry for the measurement of phase compositions and excess enthalpies of conjugate phases in amphiphilic EOR systems. 

DiAndreth, J. R. Paulaitis, M. E. In Surfactant-Based Mobility Control Progress in Miscible-Flood Enhanced Oil Recovery Smith, Duane H., Ed. ACS Symposium Series No. 373 American Chemical Society Washington, D.C., 1988 ch. 4. 

The efficiency of a micellar slug to recover tertiary oil is largely dependent on its ability to remain a single phase during the flooding process so that the oil may be displaced "miscibly" and hence, completely. However,... 

Miscible water-alternating-gas (WAG) process. Injection alternates between gas (usually natural gas or C02) and water the miscible gas and oil form one phase. The WAG cycles improve sweep efficiency by increasing viscosity of the combined flood front (Figure 12). 

Mischmetal, 5 677-678, 681 Miscibility diagrams, 22 302 Miscible flooding, 12 23 Miscible liquids, blending of, 16 687-691, 705, 712-713... 

Cosolvent flooding is an experimental method for removing DNAPLs trapped below the water table. It involves injecting a highly concentrated aqueous mixture of solvents, such as alcohols, a chemical that is miscible with either phase in the aquifer. This process has the tendency to increase or enhance DNAPL (or LNAPL) solubility greatly, and to reduce the NAPL-water interfacial tension. Depending upon the phase behavior between the cosolvent and NAPL, a cosolvent flood can be developed to emphasize either enhanced dissolution (i.e., use of methane flooding for the dissolution of TCE) or NAPL mobilization. 

Miscible Recovery. Oil and water do not mix and they do not flow with equal facility through a porous rock. Over the years, many miscible flood processes have been tested, the most successful of which have been (1) hydrocarbon misdble recovery (2) carbon dioxide miscible flooding and (3) chemically enhanced recovery. 

Immiscible carbon dioxide displacement injection of carbon dioxide into an oil reservoir to effect oil displacement under conditions in which miscibility with reservoir oil is not obtained see Carbon dioxide augmented water-flooding. 

Lunn, S. R. D. Kueper, B. H. Risk Reduction during Chemical Flooding Preconditioning DNAPL Density In Situ Prior to Recovery by Miscible Displacement, Environ. Sci. Technol, 1999, 33, 1703-1708. 

Schramm, L.L. Mannhardt, K. Novosad, J.J. Selection of Oil-Tolerant Foams for Hydrocarbon Miscible Gas Flooding in Proceedings, 14th. International Workshop and Symposium,... 

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