Waterflooding cyclic

Cyclic waterfloods were run in sequence and are indicated by a test number (T ) and flood number (F ). Stages of injection that involved changes in brine composition are indicated as a, b, and c. The cyclic waterflood was to make cyclic use of the same core to run several repeated floods, and before each flood, Swi was reestablished and aging with oil was repeated. From Figure 3.4, we can see the following ... 

The observed increase in waterflood recovery indicated that rock surface wettability might be changed as a result of cyclic waterflooding—from Flood 1 (TlFl) to Flood 3 (T1F3). 

FIGURE 3.4 Effects of changes in injection brine composition on the recovery of CS crude oil during cyclic waterflooding of a CS core (a) cyclic waterflooding of CS sandstone, and (b) pH of effluent brine and pressure drop. Source Tang and Morrow (1999). 

Steam is injected into a reservoir to reduce oil viscosity and make it flow more easily. This technique is used in reservoirs containing high viscosity crudes where conventional methods only yield very low recoveries. Steam can be injected in a cyclic process in which the same well is used for injection and production, and the steam is allowed to soak prior to back production (sometimes known as Huff and Puff). Alternatively steam is injected to create a steam flood, sweeping oil from injectors to producers much as in a conventional waterflood. In such cases it is still found beneficial to increase the residence (or relaxation) time of the steam to heat treat a greater volume of reservoir. 

TFSA molecules have been extensively and successfully used as steam additives in cyclic steam operations(27-32). Recently, results of a TFSA-waterflood which was conducted in West Texas were reported(33). The purpose of the work described in this paper was to further evaluate the feasibility of recovering incremental oil in a mature waterflood by injection of surfactants which change the wettability of reservoir rock surfaces. In this paper, we present the results of laboratory studies with Thin Film Spreading Agents and the results of a carefully conducted TFSA-waterflood pilot in the Torrance Field located in the Los Angeles Basin of California. 

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