(Sharecast News) - BHP Billiton will begin returning the proceeds from the sale of its onshore US oil and gas assets immediately.The $10.4bn of funds would be returned via two channels, a $5.2bn off-market buy-back of stock, which was to commence immediately, and the remainder through a special dividend the date of which would be set once the share repurchases had concluded and be payable in January 2019, the company said in a statement.Melbourne, Australia-based BHP had already announced that the details of the form and timing for the distribution of any proceeds would be announced on Thursday.According to its chief, Ken Mackenzie: "We believe that the off-market buy-back and special dividend program announced today will return significant value to all our shareholders, allowing the entire BHP global shareholder base to participate, both directly and indirectly, in the shareholder return program."The above will bring the total amount of cash returned to shareholders over the past two years to $21.0bn.