A system includes a well fluid diversion assembly configured to pump a volume of wellbore fluid from a first well to a second well of a single drilling or production platform or of different drilling or production platforms. The diversion assembly includes a first flexible tubing releasably connected to an outlet valve of a wellhead assembly of the first well and a second flexible tubing releasably connected to a wellhead assembly of the second well. The diversion assembly also includes a flowmeter and a sampling valve configured to selectively flow a portion of the volume to a fluid sampling port.