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Technology opens the door to deep gas

The greatest challenge facing the future of Bass Strait gas is the size of the remaining discovered undeveloped fields.

“We have a vast suite of advanced technology to assist us in evaluating and developing resources,” explained New Reservoir & Developments Supervisor Mike Gilbert.

“However, due to the small size of the fields some of this technology is precluded because of the cost.

“For example, with complex fields the design of the development concept is critical because choosing the wrong kit could have significant implications for our ability to maximise recovery of the gas.

“With a large field we would typically drill two or more delineation wells to assist with the development design. But with small fields it is difficult to justify the cost of additional appraisal drilling prior to development.”

This is where ExxonMobil’s extensive knowledge and experience in the Gippsland Basin becomes critical. The story becomes even more challenging as the company plans developments for deeper, more complex fields.

“Most of our major gas fields are in the top of the Latrobe (TOL) formation, like Marlin, Barracouta and Snapper. These are large reservoirs with clean, porous marginal marine sands,” said Mike. “Think of the clean beach sand you see on today’s surf beaches such as Gippsland’s Ninety Mile Beach.

“These fields flow extremely well, they tend to be rich in valuable liquids, and require minimal wells per unit of gas to produce. The deeper fields we are now working on consist of tighter, dirtier reservoir sands. More like the in-land rivers, lakes and estuaries of Gippsland many millions of years ago.

“They are highly compartmentalised, consisting of layer upon layer of vertically stacked reservoirs – many up to 40 individual sands ranging from 0.5 metres to 10 metres deep. They are extensively faulted and sometimes with the presence of volcanic intrusives, which break them up even further.

“Again the number of wells, well location and down-hole completion design are critical to our success.”

A Bass Strait developments taskforce is applying a suite of the latest technological advances to assist with their task.

“We have reprocessed seismic data captured back in 2001–2002 using new advanced technology,” said Mike. “This gives us a clearer picture of these deep reservoirs.

“We have used the latest 3D geological modelling and simulation to help us with project planning and reserves production forecasting.

“With reservoirs adjacent to our producing fields, we have also used time-lapse seismic modelling to better understand the movement of hydrocarbons over the years.”

The taskforce is studying options for applying the latest in drilling and engineering technology such as smart down-hole completions, cased-hole logging techniques, high grade steels, remotely operated wellheads, and advanced mathematical modelling to better understand pipeline flow assurance and drilling.

Photo — ExxonMobil assembled a team of international experts to study future development options for Bass Strait. With technology advancing exponentially in every aspect of field development, the idea was to bring the very latest in the world’s expertise together in one room.

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