hi, you have not mentioned name of the contractor nor gas company. there is no gurantee for extension of contract. they might need your services only for a limited period of six months.

however, if the offer is very good and if you are seriously interested, you may take long leave or whatever leave available from your present employer and join them. if this contractor is extending your contract for long time, you may decide that time either to resign from your employer in your home country or not to continue with this contract in Qatar.