Drysdale's 36-hole score of 11-under 131 had him in the clubhouse a step ahead of Oliver Bekker and Michael Hey at the halfway point of the South Africa tournament.
Drysdale birdied the first two holes on the West Course at the Royal Johannesburg and Kensington Golf Course and turned in an unflappable round despite lightning that delayed play.
"I'm very pleased, especially after playing well Thursday ad just keeping it going," said Drysdale.
On Saturday Drysdale returns to the East Course where he shot a 65 on Thursday.
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