Boston equity firm Advent International said it would buy oil industry software specialist P2 Energy Solutions Inc. of Denver for an undisclosed sum. Advent is buying the company from Vista Equity Partners and leaving its management team in place, The Wall Street Journal reported Monday. P2 Energy Solutions creates software that allows oil companies to monitor their business. Vista bought the company in 2008, the Journal said. After it was purchased, P2 began buying other oil-industry software specialists, including ISS Group Ltd, an Australian company it purchased for $43 million. In the fall of 2012, P2 refinanced debt and paid its owners $298 million in a dividend payment. In the year prior to the refinancing, sales were at $150 million, data from S&P Capital IQ LCD showed.