The company said it estimates the Jansz field, which extends from permit WA-18-R into the adjacent WA-267-P block, could approach 20 trillion cubic feet (TCF) of recoverable sales gas. ExxonMobil announced in March 2003 that appraisal drilling on the Jansz field in WA-18-R had indicated a field size in excess of 2,000 square kilometres with an interpreted 400 metre gross gas column.

The field is approximately 200 kilometres off Karratha, on the northwest coast of Western Australia. The well was drilled in 1,340 metres of water to a total depth of approximately 2,900 metres below sea level.

"ExxonMobil is encouraged by the results of the production test. The Jansz field represents around 40 percent of the undeveloped, discovered gas resources in the deepwater Carnarvon Basin." said Jon Thompson, President of ExxonMobil Exploration Company.

ExxonMobil holds a 50% equity interest, and is operator of the WA-18-R permit in which the Jansz-3 well was drilled, and a 25% equity interest in the adjacent WA-267-P block.

ChevronTexaco holds the remaining 50 percent equity interest in WA-18-R, while the remaining equity in the adjacent WA-267-P block is held by ChevronTexaco (50%, operator), Shell (12.5%) and BP (12%).

The well was drilled by the Glomar Jack Ryan which has now departed for Asian waters.