Mobility-controlled flood results

These results imply that since residual crude oil composition changes as it undergoes extraction by injected COj, the optimum COj mobility control agent may change during the course of the COj flood. 

Results of Immiscible Displacement Tests. The results of the tests show that immiscible carbon dioxide flooding followed by waterflooding is effective in increasing the oil recovered from a core. The oil recovered by a conventional waterflood was equal to about 30.4% of a pore volume, PV. Immiscible carbon dioxide flooding increased the recovery to a total of 50.5% PV. The addition of a mobility control agent increased the recovery further to 58.3% PV this amounts to 39% additional tertiary oil due to the effectiveness of the mobility control in the carbon dioxide immiscible process. 

The average oil produced in the two initial waterfloods was 305 cc. With an initial oil volume of 870 cc, the recovery in the initial waterflood phase is 35% of the original oil in place. The total oil produced in the case of the conventional carbon dioxide flood was 510 cc which is 58.1% of the initial oil. When mobility control was used the total oil recovered increased to 585 cc which represents 67.4% of the original oil. A summary of the results are shown in Table II. 

Fiori and Farouq Ali (73) proposed the emulsion flooding of heavy-oil reservoirs as a secondary recovery technique. This process is of interest for Saskatchewan heavy-oil reservoirs, where primary recovery is typically 2-8%. Water-flooding in these fields produces only an additional 2-5% of the original oil in place because of the highly viscous nature of the oil. In laboratory experiments, a water-in-oil emulsion of the produced oil is created by using a sodium hydroxide solution. The viscous emulsion formed is injected into the reservoir. Its high viscosity provides a more favorable mobility ratio and results in improved sweep of the reservoir. Important parameters include emulsion stability and control of emulsion viscosity. 

This chapter reports adsorption data for a number of surfactants suitable for mobility control foams in gas-flooding enhanced oil recovery. Surfactants suitable for foam-flooding in reservoirs containing high salinity and hardness brines are identified. The results of adsorption measurements performed with these surfactants are presented surfactant adsorption mechanisms are reviewed and the dependence of surfactant adsorption on temperature, brine salinity and hardness, surfactant type, rock type, wettability and the presence of an oil phase is discussed. The importance of surfactant adsorption to foam propagation in porous media is pointed out, and methods of minimizing surfactant adsorption are discussed. 

Emulsions are commonly produced at the wellhead during primary (natural pressure driven) and secondary (water-flood driven) oil production. For these processes the emulsification has not usually been attributed to formation in reservoirs, but rather to formation in, or at the face of, the wellbore itself [154]. However, at least in the case of heavy oil production, laboratory [162] and field [156,157] results suggest that W/O emulsions can be formed in the reservoir itself during water and steam-flooding. Macroemulsions, as opposed to microemulsions, can be injected or produced in situ in order to either for blocking and diverting [158,159], or for improved mobility control [160]. 

Polymers used for mobility control are non-Newtonian fluids, and thus, the polymer mobility in porous rock varies with frontal-advance rale, as illustrated in Fig. 5.95.By selecting polymer concen-tratian, it is usually possible to meet the design mobility. Data presented in Fig. 5.95 were obtained from laboratory tests on small reservoir core plugs. Polymer mobility tests should be conducted at the ROS expected for chemical flooding to include the effects of permeability reduction resulting from the chemical flood ROS. 

Performance of a pilot flood in eastern Kansas indicates improved recovery and accelerated production resulting from mobility ratio control obtained by adding a high molecular weight polymer to injected water. Ultimate pilot flood recovery of the 75-cp reservoir oil is anticipated to be 350 bbU acre-ft during the six-year flood life. Cumulative recovery to date totals 242 bbl/acre-ft after 30 months of injection. 

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous hydrophobic organic contaminants in the environment. They tend to be associated with particles and are widely transported by flooding and atmospheric pathways, resulting in elevated concentrations in sediments/soils. Coal and coal-derived particles in natural sediments/soils can act not only as strong sinks for the PAHs, but also as veiy important sources of PAHs in sediments/soils. The understanding of the mobility of these contaminants from the sediments/soils, especially the sequestration of PAHs by coal and coal-derived particles is very important, because they can control the transportation, bioavailability, degradation and hence the potential risk of these contaminants in the enviromnent. 

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