The deepest pipeline "hot tap" in the U.S. Gulf of Mexico, and possibly the world, was recently accomplished in 630 ft of seawater, according to Offshore Petroleum Divers Inc. (OPD) which carried out the dive.
The hot tap, in South Pass Block 50, connected a newly constructed BP Exploration 8-in. pipeline to an operational 10-in. oil pipeline for Chevron Pipeline Co.
Hot taps enable operators to attach an ancillary pipeline to an operational or "hot" pipeline.
The procedure avoids construction of additional pipelines to a production platform.
A team of four divers, working from the SAT Diver I--a purpose-built divine barge-drilled through the flow line (0.844 in. W.T.) to install a 10-in. x 8-in. mechanical hot-tap tool supplied by HydroTech Systems Inc., Houston. Total installation time was approximately 50 hr.
To avoid frequent decompression, the diving team lived in a pressurized saturation diving unit until the hot tap was completed.
Other recent hot tap installations by OPD include an 18 in. x 12 in. HydroTech clamp in 183 ft of water for Southern Natural Gas at West Delta Block 75 and a hyperbaric weld installation of a 20 in. x 16 in. HydroTech hot tap saddle in the Bay of Campeche in 250 ft for Corporacion de Construcciones de Campeche (CCC) under contract to Petroleos Mexicanos.
For this latter project, OPD divers in saturation working onboard CCC's lay-barge DLB 269 used a specially designed welding habitat.
The 400-ton spar unit, complete with hydraulic pipe-alignment devices, was used to accomplish the hyperbaric welding.
Copyright 1992 Oil & Gas Journal. All Rights Reserved.
