After three more days of buying, Warren Buffett's Phillips 66 shopping spree is nearing a billion dollars for the year.

In a new filing, Buffett's Berkshire Hathaway reveals that on Monday, Tuesday and Wednesday of this week the company purchased another 1.7 million shares of the energy giant for almost $132 million.

Over 15 days of buying since Jan. 4, Berkshire has spent $964 million to add 12.5 million shares to its Phillips 66 stake.

The new purchases were made between $77.40 and $78.53. Average price paid overall for the January and February buys is $77.13.

At midday Thursday, PSX was up 1.8 percent to $80.56, giving Berkshire a very short-term profit on paper from the new shares of almost $43 million.

Berkshire's 74 million-share stake is now worth $5.9 billion and represents around 14 percent of the company's outstanding shares. (You can follow the market value of this stake, and Berkshire's other publicly disclosed holdings, with the Berkshire Hathaway Portfolio Tracker.)