assign 2 $args to one wp_query

array_merge does not work the way you expect/need it to, but honestly I am not sure why you are making this so complicated. All you need is:

$args = array(
  's'         => 'keyword1 keyword2',
  'orders'    => 'DESC',
  'showposts' => 60
);
// var_dump($args); // debug
$query = new WP_Query($args);
var_dump($query->request); // debug

The built is search parser will break the s string on the spaces and construct a functional query for the terms.