A new method is proposed for screening surfactants suitable for foam diversion purposes. Surfactant screening is an important task in the processes that involve the use of foam. Several screening methods have been developed, including static tests and porous media tests. However, they are neither dependable nor standard. Six different surfactants are tested in this study. These surfactants were selected among a foray of 'best-performing' surfactants supplied by six service- and chemical companies.

The new technique requires an inexpensive setup, a simple experimental procedure, and simple calculations. A new surfactant screening technique was developed in which optimum values of parameters such as ultimate liquid recovery, recovery at breakthrough, cumulative liquid produced to cumulative air produced (L/A) ratio, maximum blocking pressure, liquid mobility ratio (PZ/PI) and breakthrough time during the porous media tests, were used to select the surfactants that are most likely to help diversion.

A series of coreflood tests, both in a single core and a dual- /t-e, was conducted in order to compare the ranking that was obtained following the high-permeability porous media tests. The results are in excellent agreement. Also, bottle tests were conducted and it was demonstrated that the bottle test results do not match the results of high-pressure core flood tests. Some porous media tests were conducted in the presence of residual oil in the system. Results indicate that for screening of surfactants, it is not necessary to have oil in the system. This observation was supported by dual-core diversion tests conducted in the presence of oil. Similarly, there is no need to use acid during the screening process.

The proposed screening method can be applied in both foam acidization as well as enhanced oil recovery processes. The method uses porous media and standardizes the surfactant screening procedure.


Acidization is considered to be the most commonly used well stimulation technique. Acidization is used to remedy wellbore damage, caused by drilling fluids or simply to increase the permeability in the vicinity of the wellbore. Quite often, the formation is heterogeneous and the acidization becomes an inefficient method due to channeling through highpermeability zones. The problem is more complex when a carbonate formation is acidized. Because the whole matrix can react in the presence of acid, leading to the formation of worm holes, artificial heterogeneity is induced. The acid is spent in the zone of highest permeability, leaving the tighter formation (the one that needs the acidization the most) unaffected. The use of commingled acid (nitrogen and acid/surfactant) has been suggested in order to produce divert the acid to lowpermeability zones. However, the success of a foam/acid injection technique depends largely on the effectiveness of the surfactant used in the process. Each service company claiming to have the most effective surfactant, it is becoming increasingly difficult for the operating companies to decide on the type of surfactant to be used during a particular acidization operation.

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