Layer reservoirs

Bioturbation, due to the burrowing action of organisms, may connect sand layers otherwise separated by clay laminae, thus enhancing vertical permeability. On the other hand, bioturbation may homogenise a layered reservoir resulting in an unproducible sandy shale. 

If gas export or disposal is a problem gas re-injection into the reservoir may be an alternative, although this implies additional compression facilities. Gas production may be reduced using well intervention methods similar to those described for reducing water cut, though in this case up-dip wells would be isolated to cut back gas influx. Many of the options discussed under water treatment for multi-layered reservoirs apply equally well to the gas case. 

In a single-layered reservoir, an orifice is formed when the pressure mounts inside the reservoir owing to the expansion of the osmotic composition. In the multilayered reservoir, the water-soluble layer dissolves when the dosage form comes in contact with the release medium. The number of exit orifices depends on the required rate of release.20... 

Since antigen(s) and antibodies are located in different sites (layers, reservoirs) at the beginning of the experiment, in all cases one or both have to move so that they meet in the gel in concentrations and proportions suitable to give a visible precipitate. The cause of this movement may merely be the thermal molecular agitation which results in diffusion. Alternatively, one or two of the reagents may migrate as a result of an electric field (electrophoresis). In the latter case, diffusion, which cannot... 

When a layered reservoir has high permeabihty contrast in vertically different layers, polymer can be injected through separate layers to control the injection profile, as mentioned previously. Another method is alternate injection of polymers with different molecular weights (MW). As discussed in Section 5.4.4, high MW polymer can be used in a high-permeability reservoir, and low MW polymer must be used in a low-permeability reservoir. For the alternate injection, the layers are grouped into different permeability layers high, intermediate, and low. 

Vela, S., Peaceman, D.W., Sandvik, E.I., 1976. Evaluation of polymer flooding in a layered reservoir with crossflow, retention and degradation. SPEJ (April), 82-96. 

Backing layer Reservoir Membrane Adhesive layer Release liner... 

Dupuis, D., A. Rougier, R. Roguet, C. Lotte, and G. Kalopissis. 1984. In vivo relationship between horny layer reservoir effect and percutaneous absorption in human and rat. /. Invest. Dermatol. 82 353-358. 

Figure 8. Example of radial surfactant propagation in a layered reservoir.

As an example, some of the adsorption levels in Figure IS will be applied to the layered reservoir in Figure 8. The anionic DPES—AOS adsorbs at 0.11 mg/g on sandstone from 2.1% TDS reservoir brine. At this adsorption level, the surfactant can propagate 369 m in the upper, high-permeability layer. The betaine is comparable to the anionic surfactant in terms of gas mobility reduction. However, it adsorbs at 1.3 mg/g on sandstone from the same brine and would only propagate 109 m in the high-permeability layer. In a limestone, on the other hand, the betaine would travel 223 m compared to 20S m for the anionic surfactant. 

PERMEABILITY IN LAYERED RESERVOIRS FIELD EXAMPLES AND MODELS ON THE EFFECTS OF HYDROFRACTURE PROPAGATION... 

Brenner, S.L. Gudmundsson, A. 2001. Permeability development during hydrofracture propagation in layered reservoirs. Norges Ge-ologiske Unders0kelse Bulletin 439 pp. 71-77. 

Reservoir layer chemically similar to outer control layers Reservoir layer chemically dissimilar to outer control layers Matrix devices... 

FIG 5 DEPENDENCE OF POLYMER CROSSFLOW ON VERTICAL PERMEABILITY OF 2-LAYER RESERVOIR... 

The results presented here are for only a narrow range of cases However, experience shows that the same mechanisms apply across a wide range of geological structures and fluid properties, including three-dimensional layered reservoirs and partially adsorbing pol3rmers. 

CROSSFLOW OF OIL IN 2-LAYER RESERVOIRS OF DIFFERENT VERTICAL PERMEABILITY... 

VELA, S., PLACEMAN, D. W. and SANDVIK, E. I., "Evaluation of Polymer Flooding in a Layered Reservoir with Crossflow, Retention and Degradation", SPE 5102, 49th Ann. Fall Conf. of SPE, Houston, Texas, 6-9 Oct., 1974. 

Figure 8.13. The effects of local cooling in the two-layer reservoir model after 4 years of water injection, (a) AZ = 20 ft (b) AZ = 100 ft initial temperature 200°F, water injection temperature 70°F (for details see Clifford and Sorbie, 1985).

This section will examine in detail the mechanisms of incremental oil recovery in the polymer flooding of heterogeneous (layered) reservoirs. It is shown... 

This issue is discussed and illustrated using simulation results from a very simple two-layer reservoir with high- and low-permeability regions. This allows the illustration of the effects of a number of parameters on the basic fluid cross-flow mechanisms which occur. The dependence of cross-flow on features such as reservoir permeability contrast, vertical/horizontal permeability ratio (kjkx) and the relative thickness of the layers is examined. Although the cross-section is sufficiently simple to allow the performance of a wide range of sensitivities, it does capture the basic flow mechanisms very satisfactorily. This is shown later in results from much more realistic models which have been taken from real field systems. 

Figure 8.19. Simplified description of polymer cross-flow in a two-layer reservoir (a) schematic diagram and (b) corresponding pressure profiles with and without cross-flow (Clifford and Sorbie, 1985).

Figure 8.23. Timing of incremental oil production as a function of vertical permeability of a two-layer reservoir (Clifford and Sorbie, 1984).

Conclusions on polymer recovery mechanisms for a simple two layer reservoir... 

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