Challenges, payoffs on deep shelf

The Gulf of Mexico's deep shelf has operators extolling enthusiasms and facing down challenges, speakers said during the International Association of Drilling Contractors' Gulf of Mexico drilling conference in Houston on Dec. 9.

The Gulf of Mexico's deep shelf has operators extolling enthusiasms and facing down challenges, speakers said during the International Association of Drilling Contractors' Gulf of Mexico drilling conference in Houston on Dec. 9.

Jim Dodson, president of James K. Dodson Co., said his company has recently focused on trouble time - downtime - associated with drilling in water depths less than 600 ft. The company, which devised the mechanical risk index (MRI) to determine risk of various wellbores, found in its GoM shelf study that many incidents - roughly 77% - with deep gas and shallow gas wells are attributed to stuck pipe, cement squeeze, lost circulation, weather, and rig equipment failure

"As MRI rises, you get fewer ROP," he said.

Dodson said the impact of trouble time decreased ROP an average of 116 ft in shallow gas wells and an average decrease of 68 ft in deep gas wells.

Robert Meize, offshore division drilling manager at Anadarko Petroleum Corp., called the relatively unexplored deep shelf very exciting, despite the funds necessary to drill wells below 15,000 ft TD.

"As we get more information and more confidence ... we'll be able to keep pushing these holes deeper and deeper," he said.

Meize said it's important to plan cement volumes as well as run full-cycle well construction models to understand drilling and production loads.

In fact, he added, the company has altered its cementing philosophy to use less cement.

El Paso Production, a deep shelf veteran, has shown success with its South Timbalier block 189/204 find. That deep shelf field had flow rates of 380 MMcf/d and 26,000 b/d of condensate in 2002.

The field is "a really good testimony to what the potential of the deep shelf really is," said Reese Mitchell, worldwide drilling vice president at El Paso Production Co.

But going that deep poses a series of issues the operator must consider, he added. Drilling challenges include well design, pore pressure prediction, casing design and casing point selection, rig and mud system selection, well control, and areas for improvement, he said.

"There's no room to stumble on these types of wells," he said.

Casing design and casing point selection is "probably the most critical factor in success," he added.

William D. Grimes, staff chemical/corrosion engineer for EP Americas at Shell Exploration & Production Co., said the supermajor is vigilant in its efforts to avoid problems with hydrogen sulfide stress cracking. Shell uses the higher value of the JT Smith correlation and bottomhole gas sampling to predict high levels of hydrogen sulfide. He said this approach is the only option to reasonably estimate potential hydrogen sulfide available.

(12/9/03)

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