To the extent that the sacrificial agent complexes with polyvalent cations in {HEAD ~ the formation fluids}, there will be less polyvalent cations left for {TAIL ~ the surfactant} to interact with 
To the extent that the sacrificial agent complexes with polyvalent cations in { HEAD ~ the formation fluids } , there will be less polyvalent cations left for { TAIL ~ the surfactant } to interact with
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH