Drilling zero discharge offshore Brazil in an environmentally sensitive area
Perry Morris - El Paso Oil & Gas
Keith Browning, Kevin Redfern - Halliburton
One key element of the El Paso Oil & Gas exploration program offshore Brazil during the recent drilling and completion of the Acai and Cacau exploration wells in the Camamu basin was to ensure compliance with a zero discharge policy. The wells were in a shallow 23 m (75.5 ft) water depth, near shore and 11 km (6.8 mi) from an extremely environmentally sensitive area. Brazilian authorities designated the coastal area as a future recreational development.
Equipment outlay
El Paso contracted Halliburton’s Baroid Surface Solutions services to provide equipment and personnel at the rig site to transport cuttings and drilling waste to a dedicated cuttings barge. To protect the delicate subsea reef environment and the nearby Camamu white sand beaches, El Paso installed booms completely surrounding the Todco 156 rig. The dedicated cuttings barge was moored outside the booms to allow access to the barge for dumping cuttings further out into deepwater. This configuration resulted in a greater distance than normal for cuttings transportation.
The distance from the rig to the barge, combined with distance needed to pump the cuttings across the rig’s main deck, down to sea level, across the water, and then up to the main deck storage tanks on the cuttings barge, meant that cuttings and waste had to be safely, efficiently, and reliably transported approximately 90 m (295 ft).
Drilling parameters
The wells were drilled with a KCl water-based mud (WBF) treated with a polymer for shale stabilization. The well design and drilling parameters dictated that the cuttings transportation system had to collect and transport the cuttings generated from all well intervals including the 26-in. and 17 ½-in. hole sections. In particular, these large hole diameter intervals were drilled at rates of penetration (ROP) reaching 60 ft/hr (~20 m/hr), consequently generating up to 20 cu m (125 bbl) of cuttings per hour.
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The Acai and Cacau exploration wells in the Camamu basin are in a shallow 23 m (75.5 ft) water depth near shore.
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The solids control system on the rig included the following:
- Three linear motion shakers
- One linear motion mud cleaner
- One 16/2 mud cleaner with 16 x 4-in. and 2 x 12-in. hydrocyclones
- One decanting centrifuge.
Equipment configuration
El Paso and Surface Solutions agreed on the equipment components and configuration after examining the drilling and operating parameters, plus the limited deck space on the rig. The final system was designed to transport cuttings efficiently and reliably while preserving as much rig deck space as possible.
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Click here to enlarge image
El Paso installed containment booms completely surrounding the Todco 156 rig, with a dedicated cuttings barge moored outside of the booms to dump cuttings further out into deepwater.
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Volume 68 Issue 7
July 2008
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