Mariner Energy, Inc. reports a natural gas discovery on its "Apia" prospect in the Deepwater Gulf of Mexico located on Garden Banks Block 73. The test well, which is located in approximately 700 feet of water, was drilled to a total vertical depth of approximately 4,500 feet and encountered 102 net feet of gas pay in a single productive interval. Initial production is expected in the second quarter of 2000 from a single subsea well tied back to a host platform. Mariner owns a 100% working interest in Garden Banks Block 73, and is the operator of the block. This latest success at Garden Banks Block 73 is Mariner's second exploratory success in two attempts in 1999 and gives Mariner six exploratory successes out of ten wells drilled in the Deepwater Gulf since becoming an independent Company in mid-1996.