Oklahoma City-based SandRidge Energy Inc. has filed its IPO of an undisclosed number of shares for an undisclosed price-per-share in a total deal valued at $690 million. SandRidge had canceled its previously planned IPO in May 2006 following Tom Ward's acquisition of 29 million shares at $17.25 each for a total $500 million. Ward was then named chairman and chief executive of the company.