DUBAI, Sept 20 (Reuters) - Saudi oil and gas driller ADES Holding said on Wednesday it has set the final price for its initial public offering (IPO), implying a valuation of 15.242 billion riyals for the Saudi sovereign wealth fund-backed firm.

Reuters reported last week that the IPO was expected to be priced at 13.50 riyals a share, the top-end of a previously announced range.

ADES confirmed the pricing for the IPO, saying it drew nearly $76.5 billion in orders from institutional investors.

The firm is expected to raise about $1.22 billion from the sale of more than 338.7 million existing and new shares or about 30% of its issued share capital post-capital increase.

Reuters reported in November that the planned IPO could fetch more than $1 billion, citing sources close to the matter.

Institutional book-building has closed. Retail subscription runs from Sept. 26-28. Final share allocations are expected no later than Oct. 4. No date has yet been set for shares to begin trading.

ADES is the second company to seek a flotation on the Saudi Exchange since the summer after domestic auto rental company Lumi priced its IPO at the top of its range earlier this month.

Headquartered in the eastern Saudi city of Khobar, ADES operates a fleet of offshore and onshore rigs across the Middle East, North Africa and India. Its clients include state oil giant Saudi Aramco, Kuwait Oil Company and North Oil Company in Qatar.

SNB Capital is the lead manager. The bank and EFG Hermes, Goldman Sachs and JPMorgan are acting as financial advisers and global coordinators. The four banks are also bookrunners and underwriters, joined by GIB Capital, HSBC, Al Rajhi Capital and Saudi Fransi Capital.

Arab National Bank, Alrajhi Bank and Saudi National Bank are the receiving agents and Lazard is independent adviser to ADES. ($1 = 3.7508 riyals) (Reporting by Yousef Saba; Editing by Sonia Cheema)