화학공학소재연구정보센터
Energy Sources, Vol.21, No.1-2, 191-213, 1999
A new method for screening surfactants for foam diversion applications
Foam diversion is a promising method for diverting acid to formations that would otherwise be bypassed Even though numerous surfactants are being used by the stimulation service companies, there is no reliable or easy-to-use method for screening them. A standard method is proposed in this article. The method is validated with laboratory diversion tests conducted under high-pressure conditions using Berea sandstone cores. Seven different prescreened surfactants were selected for testing the proposed method. Several screening methods have been proposed in the past including static tests and porous media tests. However they are neither dependable nor standard. Therefore, a new 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 ratio (L/A), liquid injection pressure ratio (P2/P1), and breakthrough time during the porous media tests, were used to select the surfactants that are most likely to help diversion. Based on the new surfactant screening criteria, the overall ranking (from best to worst) of the seven surfactants used in this article was as follows: S3 --> S8 --> S2 --> S6 --> S4 --> S1 --> S5 Among these seven surfactants, four surfactants were selected for further evaluation under high-pressure diversion conditions. Diversion tests were conducted using four different permeability contrast values. This was the first time a screening criterion was tested against diversion results that were performed under high pressure and low-permeability conditions. The ranking of the screening criterion held true for the diversion tests. In order to validate the proposed screening criterion further, foam diversion results were obtained in the presence of residual oil. It was found that the presence of residual oil changed the ranking in the high-pressure diversion case. In the presence of oil, the ranking of the diversion tests was exactly the same as that determined by the screening criterion. The screening method is, therefore, proposed as a standard for selecting surfactants for diversion purposes.