NEW YORK ( TheStreet) -- Warren Buffett's Berkshire Hathaway ( BRK.A) is expanding its underwriting of the oil and gas industry. In an agreement with Willis Group Holdings ( WSH), the insurers will provide coverage up to $250 million on new policies. "This additional capacity is excellent news. It provides substantial and easy access to AA+ rated paper to the market at a time when the need for additional capacity on a range of operating and construction risks has never been greater," Willis Group CEO Alistair Rivers said in a statement. Insurance rates have increased for oil since the BP ( BP), Deepwater Horizon disaster. --Written by Maria Woehr in New York. To contact the writer of this article, click here: Maria Woehr. To follow the writer on Twitter, go to http://twitter.com/newsgirlmw. To submit a news tip, send an email to: email@example.com.