Polymer-Surfactant Interaction for Chemical Enhanced Oil Recovery in Carbonate Reservoirs

The objective of our research is to delineate surfactant-based EOR mechanisms of fractured carbonates and quantify potential incremental recovery. We create two-dimensional micromodels that are etched with representative pore networks including dual-porosity carbonate pore space.
Figure 1(a) shows a small volume from within carbonate pore space. Note the pore walls that make sharp 90° angles. Grains appear as islands and have various size. Micromodel surfaces are treated to obtain oil wetness.

At pore-scale, oil trapping and displacement is viewed using reflected light microscopy. Accordingly, this study provides the underpinnings for successful EOR in carbonate systems. From the images and data collected, we shall establish conceptual/numerical models for (i) oil recovery from fractured systems that have been pressure depleted and are subsequently subjected to chemical EOR, (ii) oil recovery from spontaneous and forced imbibition of water laden with alkali and surfactant, and (iii) incremental oil recovery from fractured carbonate systems where the oil saturation is waterflood residual.

                           (a)                                                                                 (b)

Figure 1. Micromodel details: (a) Scanning electron micrograph of carbonate micromodel pore space at 1000X; Grains appear as islands; (b) Whole micromodel indicating fluid distribution port on top and bottom of image and the red grid indicates areas of large porosity within the dual porosity pore structure.

Figure 2 presents representative results from a micromodel experiment and also illustrates the oil wetness of the micromodel surface. Note the scale bars indicating a length of 100 µm. Figure 2(a) shows a region of carbonate pore space where large and small porosity regions are adjacent. Oil is brown and the large pore in the center of Fig. 2(a) shows lightly shaded water penetrating and snapping off (disconnecting) in the large pore.  The grains are white. Figure 2(b) is an image at greater magnification after water has swept the pore space. This figure illustrates oil films coating grains (i.e., oil wetness) as well as the residual oil resulting from waterflood.

                   (a)                                                                         (b)

Principal Investigator: Professor Anthony Kovscek (Stanford), Prof. Abdullah Sultan (KFUPM)