Saudi Arabia is sure its 35,000-strong security force can protect the top oil exporter\'s installations against the rising threat of terrorist attack in the region, the former chief of Saudi intelligence services said on Monday. A wave of unrest rippling across the Arab world this year has uprooted governments and spread fertile ground for terrorist groups, Saudi Prince Turki al-Faisal said in a speech at the Royal Elcano Institute in Madrid. But Saudi remains confident the billions spent on protecting its biggest export earner makes its energy infrastructure \"immune\" from attack, even as governments from Tunisia and Egypt to neighbouring al-Qaeda base Yemen are upended all around it. \"With governance in Yemen, Libya, Tunis, Egypt, Syria and other nations in such tenuous states, the perfect conditions for terrorist cells to take root and conduct desperate, evil and anarchical acts are created,\" he said. \"However, while the general picture of Saudi Arabia\'s surroundings is predominated by this great turmoil, at the center of these many storms sits our Kingdom, which, I am glad to report, remains stable and secure.\" Saudi - which is thought to keep some \"redundancy\" in its oil export system as insurance against some facilities being disabled - started building an industrial security force in 2006 after a failed al Qaeda attack on the world\'s largest oil processing plant at Abqaiq. In 2009, around 85 percent of revenues were from oil and a surge in oil prices in 2011 should boost Saudi oil earnings to $300bn this year and average around $250bn per year for the next five years, Prince Turki said. Massive Saudi spending packages announced earlier this year have so far helped avoid widespread social discontent but have increased the kingdom\'s oil revenue needs, analysts say.