National Oilwell Varco Inc., Houston, (NYSE: NOV) plans to acquire Grant Prideco Inc., Houston, (NYSE: GRP) for approximately $7.4 billion in cash and debt. National Oilwell will pay $23.20 in cash and 0.4498 share per Grant Prideco share, a 22% premium based on closing prices as of Dec. 14. National Oilwell shareholders will own approximately 86% of the combined.