Abstract: Water-insoluble polyoxyalkylene graft copolymers are effective anti-foam agents for reducing foaming in crude oil/gas separators. The copolymers are of formula: ##STR1## wherein R is an ethylene, propylene or butene group or a mixture thereof;R' is a hydrocarbyl group containing 1 to 8 carbon atoms;R" is a hydroxyl group, an alkoxy group or an alkyl group containing 1 to 8 carbon atoms;(a) is a number in the range 100 to 250;(b) is a number in the range 1 to 6;(c) is a number in the range 1 to 10; and(d) is a number in the range 10 to 100.They are particularly useful in breaking microgas dispersions and foams resulting from crude oils with a high gas to oil ratio.

Abstract: A method for determining the stability of live foam comprises a sample pressurizing vessel connected to a sample injection chamber leading to a sample cell linked to a reference cell maintained at constant pressure. The link between the sample cell and the reference cell comprises a link fitted with a valve for initially equalizing the pressure between the two and subsequently isolating them. A differential pressure transducer is provided for determining the subsequent change in pressure of the sample with reference to the reference cell as the foam collapses.

Abstract: Polysiloxanes of specified molecular weight and molecular weight distribution are effective anti-foam agents for reducing foaming in crude oil/gas separators. They are particularly useful in breaking microgas dispersions.The polysiloxanes, preferably polydimethyl siloxane, contain not more than 10% by weight of components of molecular weight 50,000 and lower, at least 15% by weight of components of molecular weight 200,000 and higher and not more than 6% by weight of components of molecular weight 370,000 and higher, molecular weights being expressed as polystyrene equivalent molecular weights.

Abstract: Polysiloxanes of specified molecular weight and molecular weight distribution are effective anti-foam agents for reducing foaming in crude oil/gas separators. They are particularly useful in breaking microgas dispersions.The polysiloxanes, preferably polydimethyl siloxane, contain not more than 10% by weight of components of molecular weight 50,000 and lower, at least 15% by weight of components of molecular weight 200,000 and higher and not more than 6% by weight of components of molecular weight 370,000 and higher, molecular weights being expressed as polystyrene equivalent molecular weights.