In 2016, the company divested or wrote-off all oil and gas assets to focus on the growth of its core minerals business.
Late last month, it sold its 30% share in VES for net proceeds of US$4.3 million.
"We are pleased to finalise the sale of our last remaining oil and gas asset and provide a return to our valued shareholders," Imdex managing director Bernie Ridgeway said.
"Imdex has a strong balance sheet with a healthy net cash position. This enables us to continue to invest in our leading technologies and drive future growth."
All the VES sale proceeds, together with an additional A$1.4 million funded from existing cashflow, will be paid to Imdex's shareholders as a special fully franked dividend of 2c per share on November 1.
In late August, the company declared a final dividend of 1.4c after posting a full-year profit of $27.6 million.
Imdex shares rose 7.2% this morning to $1.485, just shy of the 52-week high of $1.495 reached last month.