Interactions between solutes in displacement solutions and oil bearing rocks.
Studies of adsorption of several surfactants from aqueous solution onto kaolin
have been made, such as might be employed in an enhanced oil recovery process.
Investigations of the surfactants were carned out with regard to pH, ionic
strength, temperature, the addition of short chain aliphatic alcohols, the addition
of sacrificial complexing agents and various ion-exchanged forms of kaolin. The
various forms of kaolin were synthesised to simulate the effect of clay contact
with sea water andior formation water.
To try and \lllderstand the surfactant solution more fully an attempt was made to
determine the number of bound Ca2+ ions and A13+ ions using an ion-selective
electrode and atomic adsorption spectroscopy teclUliques.
The results of the adsorption experiments show that monolayer coverage of the
kaolin takes place, and the minimum adsorption is favoured by the following
conditions: high pH, low ionic strength and elevated temperatures. The presence
of butan-l-ol and sodiwn citrate are also beneficial. In the presence of high ionic
strength solutions, the anionic surfactant may also be lost due to salt f011l1ation
with the metal ion present and hence be precipitated from solution.
In the absence of the short chain alcohols the adsorption isothe11l1s of the anionic
surfactants can be said! at low concentrations « 10-3 mol dm-3), to be due to
electrostatic interactions between the edge of the clay particles and the charged
surfactant. At higher concentrations the adsorption becomes limited due to the
formation of micelles. At concentrations> 10-2 mol dm-3 the surfactants appear
to desorb into solution. This is due to the resolubilisation of the adsorbed
surfactant-metal ion species by the excess micelles which exist at these surfactant
The detennination of bO\llld counter ions has been investigated and found to give
acceptable results comparable to those that would be expected, However, slight
reservations are made as to the total accuracy of the test method.
This study has been able to define the conditions which will allow various anionic
surfactants to be used in conjooction with other chemical species in enhanced oil
recovery processes for both land or sea based wells.