Group slates gas gathering pipeline systems off Alabama

How DIGS is Expanding [31018 bytes]

Dauphin Island Gathering Partners (DIGP), Houston, is embarking on a series of pipeline projects in the Gulf of Mexico to serve gas projects off Alabama.

DIGP aims to extend and expand Dauphin Island Gathering System (DIGS) to meet immediate needs of producers bringing new wells on line in the gulf's Viosca Knoll and eastern Main Pass federal planning areas.

DIGP is a general partnership of units of MCN Corp., Detroit; PanEnergy Corp., Houston; and Offshore Energy Development Corp. (OEDC), The Woodlands, Tex.

Project overview

DIGS work is to occur in two phases. First phase work includes installation of 60 miles of 24 in. subsea pipeline by March 1997.

In phase two, DIGP plans to construct a 15 mile, 24 in. pipeline loop from a point on the existing DIGS system in Alabama state waters north of Dauphin Island to the system's onshore terminus near Mobile.

The pipeline loop by late 1997 will boost DIGS capacity 450-550 MMcfd to more than 900 MMcfd.

The DIGS extensions and pipeline loop will provide a new gathering outlet in Viosca Knoll and Main Pass East Addition areas at a time when gas well deliverability in the region is expected to exceed the gathering system's existing capacity of 376-400 MMcfd.

The DIGS expansion also will provide the first northern outlet for gas from the East Central gulf to premium East Coast markets. Producers will be able to direct gas from DIGS into the interstate pipeline systems of Florida Gas Transmission Co., Transcontinental Gas Pipe Line Corp., or Koch Gateway Pipeline Co. through onshore interconnects in Alabama.

More project details

DIGS gathers gas from production facilities in the Mobile planning area through a system consisting of 8-20 in. lines.

Larger diameter lines are needed in the extensions because of the longer distances and higher deliverabilities of wells to be tied in. DIGP will operate the new DIGS facilities as a separate, higher pressure system and has designed components to meet the higher specifications.

Gas to be gathered by the expanded system from Viosca Knoll and eastern Main Pass is richer in liquids content than volumes handled by existing facilities. DIGP plans to transport the new supplies with liquids entrained.

DIGP in phase one plans to lay 45 miles of 24 in. subsea pipeline south from the existing DIGS to a point near Viosca Knoll Block 384.

From there, a separate partnership of Mobile Bay Gathering Co. unit of MCN Investment Corp. and Dauphin Island Gathering Co. unit of OEDC plans to lay a 15 mile, 24 in. pipeline segment to the edge of the Outer Continental Shelf near the boundary of Main Pass East Addition Blocks 224 and 225.

The MCN-OEDC units then will lay one 24 in. lateral eastward to Main Pass East Addition Block 223 and another southwest to Main Pass East Addition Block 261.

DIGP, meantime, expects to complete two smaller DIGS extensions by November 1996. Partners are planning a 3 mile, 12 in. extension from Viosca Knoll Block 80 to an Enron Oil & Gas Co. platform to be installed later this year on Viosca Knoll Block 124.

The group plans to lay 8 miles of 12 in. line from Viosca Knoll Block 31 to an aggregation point at an OEDC Exploration & Production LP platform on Viosca Knoll Block 121.

Both 12 in. extensions will be able to handle as much as 100 MMcfd of gas, but initial volumes will be much less.

To handle the larger volumes of gas and natural gas liquids gathered by extended facilities, DIGP also plans to construct a new gas processing plant near DIGS' system terminus. The plant's first processing train is to be operational by early 1998.