you can do something like this:
$args = array(
'posts_per_page' => 1000,
'post_type' => 'post'
);
$the_query = new WP_Query( $args );
if ( $the_query->have_posts() ) {
while ( $the_query->have_posts() ) {
$the_query->the_post();
$casa_id = $post->ID;
update_post_meta($post->ID, 'casa_id', $casa_id);
}
}