While not as major as its purchase of 24/7 a few weeks ago, WPP has added another online ad company to the fold. Through its marketing shop G2 Worldwide, itself a subsidiary of Grey, has bought independent digital agency Refinery, Adweek reports. Based in Hatboro, Pa., Refinery specializes in site design, search marketing and analytics. Its clients include Campbell’s, Merck and Merrill Lynch. It has 79 employees and generated $21.1 million in revenue last year. Refinery is expected to be integrated into G2 Interactive. Terms of the purchase were not disclosed.