Waterflood performance, amount

This paper presents a new recovery technique for improving waterflood performance in a fractured sandstone reservoir. The presence of fractures leads to very early water breakthrough and makes it difficult to drain the matrix of the fractured reservoir. Consequently, these fractured reservoirs are left with considerable amounts of unproduced oil. An effective technique for plugging the fractures and simultaneous treatment of the matrix to produce oil will lead to great improvement in oil recovery from fractured reservoirs. One such technique is presentee in this paper. 

During caustic waterflooding the alkali can be consumed by the dissolution of clays and is lost in this way. The amount lost depends on the kinetics of the particular reaction. Several studies have been performed with kaolinite, using quartz as a yardstick, because the kinetic data are documented in the literature. The initial reaction rate has been found pH independent in the pH range of 11 to 13 [517]. The kinetics of silica dissolution could be quantitatively described in terms of pH, salinity, ion-exchange properties, temperature, and contact time [1549]. 

Polymer injection initiated at advanced stages of waterflood. Two polymer-floods were performed in partly oil depleted sandpacks. The sequence of operations was as follows. Upon completing the brine permeability measurements, a sufficient amount of oil (20 PVI) was pumped through the sandpack. After saturation with oil, a regular brineflood was performed, applying a 6 ft/day frontal advance rate. Thereafter, the sandpacks were resaturated with oil. 

The propoxy ethoxy sulfonate used by Taugbpl et al. [14] also showed an IFT value close to 10 mN/m towards n-heptane in seawater. Figure 7. Thus, the present PO-EO-surfactant systems are able to lower the IFT between water and oil by a factor of more than three magnitudes in a Type II( —) phase behavior. The corresponding increase in the capillary number suggests that a significant amount of waterflooded residual oil will be recovered by a chemical flood performed in the two-phase region. 

Pilot flood performance to date and the anticipated recovery of 350 bbl/acre-ft indicate both improved rate and amount of recovery when compared with conventional waterfloods exhibiting similar reservoir parameters. Fig. 9 compares the Vernon polymer flood performance with that of a number of conventional Squirrel water-floods in eastern Kansas." The wide range of brine flood recoveries is attributed in part to variations in oil viscosity with the better cumulatives obtained from lower oil viscosity reservoirs. Although other reservoir parameters may also differ, comparison of acre-foot recovery as a function of acre-foot injection clearly demonstrates greater recovery efficiency from the polymer flood. 

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