By purchasing the 21 million shares at $75 a share, Occidental Petroleum completed the first stage of its $3-billion takeover of the natural gas pipeline operator. Occidental said 35.9 million of Midcon's 41.5 million shares were tendered under the offer. The 21 million shares were purchased on a pro-rata basis of 58.5% of those tendered. Under the second phase of the merger, Occidental will exchange 2.25 of its shares for each of Midcon's remaining shares. The stock swap has been valued at $69.75 per share.