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Chevron's dual gradient drillship arrives in Gulf of Mexico

Chevron Corp. said the Pacific Santa Ana, a deepwater drillship built with the capacity to perform dual gradient drilling (DGD), has arrived in the Gulf of Mexico to work for Chevron under a 5-year contract with a subsidiary of Pacific Drilling SA.

Conventional deepwater drilling uses a single drilling fluid weight in the borehole, but DGD uses two weights of drilling fluid: one above the seabed and another below.

The two weights allow drillers to more closely match the pressures presented by nature and effectively eliminates water depth as a consideration in well design, Chevron said. DGD also allows drillers to more quickly detect and react to downhole pressure changes, enhancing deepwater drilling safety.

"Pacific Santa Ana will enable us to demonstrate dual gradient drilling, which has the potential to change the way deepwater wells are drilled," said George Kirkland, Chevron vice-chairman. "This new process builds on our record of technology leadership in deepwater."

The Pacific Santa Ana is Chevron's fifth drillship in the deepwater gulf. It is equipped with a DGD riser, a mud lift pump handling system, six mud pumps (three for drilling fluid and three for seawater), extensive fluid-management system enhancements, and more than 72,000 ft of DGD-related cables. After additional equipment is installed and tested, Pacific Santa Ana will be used for exploratory and development drilling in the deepwater gulf.


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