Use of Fluorochemical Surfactants in Nonaqueous Stimulation Fluids

Abstract

This paper discusses a fluorochemical surfactant that is surface-active in hydrocarbon liquids such as kerosene and xylene and can function as an effective foaming agent for these liquids. A new apparatus for evaluating foaming capability in the laboratory is described, and data for hydrocarbon liquids foamed with this surfactant using this apparatus are presented. Field tests are described. Introduction Various types of foamed aqueous stimulation fluids have found considerable use in the oil field, but in many instances water can damage a formation, and foamed hydrocarbon liquids would be preferable. In addition, there are cases where foaming of hydrocarbon solvents would make them more efficient and where condensate removal by foaming would be desirable.A fluorochemical foaming agent has been developed which is capable of foaming nonpolar hydrocarbon liquids such as kerosene, xylene, and condensate for a variety of oilfield applications. This fluorochemical, identified as FC-C in this article, is a mixture of nonionic fluorochemical surfactants belonging to the chemical class of fluorinated alkyl esters. Other fluorinated alkyl esters were less effective in foaming nonpolar hydrocarbon liquids, but some showed greater surface tension reduction in hydrocarbons and some foamed alcohols. Laboratory foaming data on FC-C, and three field tests illustrating various applications of this foamer, are discussed. Laboratory Experiments To study the foam-generating capabilities of this fluorochemical surfactant, a foam generator was constructed; the apparatus and experimental procedure for its use are discussed in detail in Ref. 4. This equipment and procedure appear to provide a valuable and reproducible method for determining the foaming characteristics of liquids.Using this apparatus, the procedure to test foam consists of placing a liquid in a suitable vessel so it can be subjected to a constant pressure of 150 psi (1 MPa), passing the liquid through an aspirating inline generator, and collecting the foam in a tared graduated cylinder for measurement of foam quality and half-life. Foam quality is defined as percent by volume of gas phase in the foam, and half-life is defined as the time required for one-half of the liquid in the foam to drain from the foam, regardless of whether the foam actually breaks or simply drains.Using this procedure, hydrocarbon liquids were foamed using FC-C, and foam data are summarized in Table 1. For comparison, this table includes equivalent data for an aqueous foam generated by this same procedure, using a well-known aqueous foamer (Adofoam BF-1(TM) from Nalco Chemical Co.). It is evident that under these conditions, FC-C at 0.1% (solids) foams kerosene and diesel oil about as effectively as the aqueous foamer foams water at 0.5% (solids). It also produces good foam in xylene and fairly good foam in 55 degrees API gravity (0.75-g/cm3) condensate but does not foam hexane. JPT P. 1695＾