altagas ltd said tuesday that it is considering offering hybrid subordinated debt securities to repurchase its series k preferred shares the calgarybased energy infrastructure company didnt reveal any details as to the size of the potential offering but said it would be used to redeem or repurchase outstanding cumulative redeemable fiveyear rate reset preferred shares series k the company cautioned that there is no certainty that it will complete the offering nor in the timing or the terms