Sorting posts by custom field value in array

I have a custom field value that is an array and it has date as one of the values:

a:3:{s:4:"date";s:10:"03/06/2013";s:6:"target";d:1000;s:8:"currency";s:3:"USD";}

I'm trying to sort posts with this date but I'm having trouble doing it.

Here is my query:

   $args = array (
            'showposts' => -1,
            'post_type' => 'project',
            'orderby' => 'meta_value',
            'order' => 'ASC',
            'meta_query'  => array(
                       array(
                        'key' => 'date',
                        'value' => date('m/d/Y'),
                        'compare' => '>=',
                        'type' => 'DATETIME',
                        )
                    ),
            'cat' => $cat_id);
        $posts = get_posts( $args );