A method of cooling a boil-off gas stream from a liquefied gas tank using a single mixed refrigerant comprising at least the step of heat exchanging the BOG stream with the SMR in a liquefaction heat exchanger system comprising a single liquefaction heat exchanger to provide a cooled BOG stream, wherein the SMR is provided in an SMR recirculating system and wherein the method comprises at least the steps of: (a) compressing the SMR using at least one oil-injected screw compressor to provide a post-compression SMR stream; (b) separating the post-compression SMR stream to provide an oil-based stream and a first SMR vapour stream containing some oil carryover; (c) passing the first SMR vapour stream into the liquefaction heat exchanger system to cool the first SMR vapour stream and provide a cooled first SMR vapour stream, wherein the temperature of the cooled first SMR vapour stream is above the solidification temperature of the oil; (d) withdrawing the cooled first SMR vapour stream from the liquefaction heat exchanger system; (e) separating the cooled first SMR vapour stream to provide a liquid-phase SMR stream and an oil-free SMR vapour stream; (f) passing the oil-free SMR vapour stream through the liquefaction heat exchanger system to provide a condensed SMR stream; (g) expanding the condensed SMR stream to provide an expanded lowest-temperature SMR stream to pass through the liquefaction heat exchanger system for heat exchange against the BOG stream to provide the cooled BOG stream; (h) expanding the liquid-phase SMR stream of step (e) to provide an expanded liquid-phase SMR stream having a temperature that is still above the solidification temperature of the oil, passing the expanded liquid-phase SMR stream into the liquefaction heat exchanger system; and (i) combining the expanded liquid-phase SMR stream with the expanded lowest-temperature SMR stream in the liquefaction heat exchanger system. (a) compressing the SMR using at least one oil-injected screw compressor to provide a post-compression SMR stream; (b) separating the post-compression SMR stream to provide an oil-based stream and a first SMR vapour stream containing some oil carryover; (c) passing the first SMR vapour stream into the liquefaction heat exchanger system to cool the first SMR vapour stream and provide a cooled first SMR vapour stream, wherein the temperature of the cooled first SMR vapour stream is above the solidification temperature of the oil; (d) withdrawing the cooled first SMR vapour stream from the liquefaction heat exchanger system; (e) separating the cooled first SMR vapour stream to provide a liquid-phase SMR stream and an oil-free SMR vapour stream; (f) passing the oil-free SMR vapour stream through the liquefaction heat exchanger system to provide a condensed SMR stream; (g) expanding the condensed SMR stream to provide an expanded lowest-temperature SMR stream to pass through the liquefaction heat exchanger system for heat exchange against the BOG stream to provide the cooled BOG stream; (h) expanding the liquid-phase SMR stream of step (e) to provide an expanded liquid-phase SMR stream having a temperature that is still above the solidification temperature of the oil, passing the expanded liquid-phase SMR stream into the liquefaction heat exchanger system; and (i) combining the expanded liquid-phase SMR stream with the expanded lowest-temperature SMR stream in the liquefaction heat exchanger system.