see this answer - HTML form readonly SELECT tag/input
You should keep the select element disabled but also add another hidden input with the same name and value.
If you reenable your SELECT, you should copy it's value to the hidden input in an onchange event.
see this fiddle to demnstrate how to extract the selected value in a disabled select into a hidden field that will be submitted in the form.
<select disabled="disabled" id="sel_test">
<option value="1">One</option>
<option value="2">Two</option>
<option value="3">Three</option>
</select>
<input type="hidden" id="hdn_test" />
<div id="output"></div>
$(function(){
var select_val = $('#sel_test option:selected').val();
$('#hdn_test').val(select_val);
$('#output').text('Selected value is: ' + select_val);
});
hope that helps.