• Noble Affiliates Inc., Houston, subsidiary EDC Europe Ltd. and Shell U.K. Ltd. have exchanged North Sea assets. Shell acquired a 12.5% interest in Block 20/4b and cash for a 12.9% interest in Block 21/20a, which includes the Cook Field, which together produce about 55 million cu. ft. of gas per day. • Madison Oil Co., Calgary, plans to purchase BP subsidiary Arco Turkey Inc., which has a 19.6% working interest in the Cendere Field, in south-central Turkey, that produces approximately 2,600 bbl. of oil per day from 13 wells, 540 bbl. per day net to Arco. • Phillips, Bartlesville, Okla., subsidiary Phillips Australia WA-248 Co. Pty Ltd. plans to acquire Petroz for AU70 cents per share, or AU$158.4 million. Phillips Australia currently has a relevant interest in 19.73% of the issued capital of Petroz. • PanAfrican Energy Corp. Ltd., plans to purchase a 32.5% interest in the Etame Marin Permit offshore Gabon, operated by Vaalco Energy Inc. , Houston.