(Reuters) – Private equity firm Apax Partners and technology investment firm JMI Equity agreed to pay about $1 billion cash for software group Paradigm, whose technology helps oil and gas companies analyze drilling prospects.

Apax and JMI said on Monday they agreed to buy Paradigm Ltd which has been owned by U.S. investment group Fox Paine for the last 10 years.

Fox Paine bought the business in 2002 for around $100 million, taking the small U.S.-listed company private. The private equity firm invested another $65 million in Paradigm in 2010.

Paradigm, which competes with companies like Halliburton and Schlumberger, helps engineers to make drilling and production decisions by analyzing seismic data and producing complex three dimensional models.

The company has been for sale for more than 6 months, and has been in negotiations with Apax and JMI for more than a month, according to a source familiar with the matter. It previously considered going public, filing with U.S. regulators to begin the process in 2006.

The deal will allow Apax to tap into Paradigm’s large customer base across the United States, Europe and Asia, including Cairn Energy, Gazprom and Total, as they continue to drill and explore for resources in more challenging locations.

One of Europe’s largest private equity groups with operations around the world, Apax has had extensive experience in the software and IT sectors, investing some $1.7 billion of equity in companies including anti-virus developer Sophos and Autonomy.

Bank of America Merrill Lynch and Simmons & Co advised Apax, with UBS and Royal Bank of Canada providing debt financing. Jefferies advised Paradigm.