with q as (
  select
    to_date('25.07.2017 14:15:01', 'DD.MM.YYYY HH24:MI:SS') d1,
    to_date('28.07.2017 10:20:37', 'DD.MM.YYYY HH24:MI:SS') d2,
    9  h1,
    18 h2
  from dual
)
select
(
  case
    when d1 <= trunc(d1) + h1 / 24 then (h2 - h1) / 24
    when d1 >= trunc(d1) + h2 / 24 then 0
    else (trunc(d1) + h2 / 24) - d1
  end
  +
  case
    when d2 <= trunc(d2) + h1 / 24 then 0
    when d2 >= trunc(d2) + h2 / 24 then (h2 - h1) / 24
    else d2 - (trunc(d2) + h1 / 24)
  end
  +
  greatest(trunc(d2) - trunc(d1) - 1, 0) * (h2 - h1) / 24
) * 24 * 60 minutes
from q
;

MINUTES
----------
   1385.6

...............
  +
  (trunc(d2) - trunc(d1) - 1) * (h2 - h1) / 24
) * 24 * 60 minutes