- Reusable platforms consisting of concrete gravity bases with minimum framework or legs are seen as one solution to inexpensive field development in varying water depths. On the left is the Odfjell Drilling design (Kokstad, Norway) which uses a space frame. On the right is the Hollandsche Staalbouw Maatschappij design (Gouda, The Netherlands).
Subsea separation to be tested off Brazil in 1996
Petrobras will begin testing a twin-chamber subsea separation system using production from a live well in the Marimba Field beginning at the end of 1996. The system, based on a 1986 patent, is called Petroboost. The system is under construction.
Each of the two chambers is filled alternatively with produced fluids and gases. Compressed gas from a nearby platform is injected into the mixture, causing separation of the production into liquids and gases. The separate streams are then piped to the surface. Production from Marimba No. 1 will be piped a distance of 600 meters to the twin-chambered unit. The chambers will actually be cased boreholes drilled to a depth of 270 meters below the seabed.
Production will flow through a series of valves at the seabed into one of the two chambers. After one chamber is full, production is routed to the second. The injected gas acts as a piston to separate the lower pressure gas from the crude. Operation of the two chambers proceeds automatically.
Bruce Field experience with roller reamers yields recommendations
Extensive use of roller reamer tools on hard formations in the Bruce Field have yielded a set of recommendations on these tools. The recommendations were published recently in BP Downhole Talk Issue 44 and authored by Ken Gibson and Martin Varco.
Drilling in the Bruce Field, like others in this area of the North Sea, is characterized by abrasive formations, excessive stabilizer wear, and under gauge hole. Both drillstring and near-bit roller reamers were required. The recommendations are as follows:
- The reamer bearings should not be held by bolts without anti-backoff features. The ideal means is the split lock pin.
- Reamer bearing blocks should be flush with the tool surface and reinforced with tungsten carbide inserts.
- Upon failure, the rollers and bearings should remain a part of the body and not fall into the hole.
- The bottom shoulders of the reamer should be hard surfaced.
- In the event of bearing failure, the clearance between the tool body and roller should be sufficient to prevent damage to the tool body.
- The reamer tools can be slightly over-gauge rather than under-gauge.
- Bearings should be able to withstand severe vibration, string rotation at 200 rpm, and a total of one million revolutions.
- Oil base mud lubricated bearings and sealed bearings seem to wear at comparable rates.
- The reamers must be easy to redress. Redress kits should be available in quantity.
Pipe freeze plugs seal well for BOP installation
A wellhead production stream on a Norwegian platform was isolated by freeze plugs so that a blowout preventer could be installed. The well had to be sealed in order to repair a casing leak. The work was undertaken by Nowsco Aberdeen.
The BOP unit was required prior to the installation of a snubbing unit, which in turned allowed the placement of bridge plugs. The ice plug was developed by using nitrogen to cool a secondary medium, which was circulated inside a jacket around the pipe wall. The pipe freeze was conducted through 30-in. casing, cement, 20-in. casing, and the 13-1/2-in. tubing. Freeze gel was injected into the casing and annuli prior to the start of operations. The freeze plug formed in three days, and allowed the operation to take place without incident.
Two jackups support dual cycle generator for West Africa
- Waller Marine has designed a 160 MW power generation station for onshore electrical supply. The combined cycle gas turbines will be supported by two linked jackups, converted from drilling units.
The era of offshore gas-powered electrical generation is approaching rapidly. Waller Marine of Houston is equipping two jackups for Polar Energy that are destined to provide power for an area along the coast of West Africa.
The design calls for the conversion of two jackup drilling units and removal of drilling equipment. The jackups will support a 160 MW combined cycle generating facility. The jackups will be installed in shallow water near gas producing facilities.
The first jackup will be equipped with three GE LM 6000 turbine generating sets. The second jackup, which will be converted later, will be equipped with exhaust heat recovery boilers and a 40 MW steam turbine generator. Both units will be in place by mid-1996.
Technology conference begins; three more call for papers
The Fifth International Offshore and Polar Engineering Conference will get underway on June 11, 1995 in The Hague, The Netherlands. Calls for technical papers have been announced by three other groups - 1996 Offshore Technology Conference, 1996 Energy Week - Drilling and Production Economics, and the 1995 Louisiana Gulf Coast Oil Exposition (Lagcoe).
Attendees wishing information on the Netherlands conference should contact the organizing committee chairman: Prof. Jin Chung, Colorado School of Mines in Golden, Colorado (Tel: (01) 303-273-3573; Fax: (01) 303-420-3760).
Information on papers submission are available for the following: Offshore Technology Conference - Conference Programming, Richardson, Texas - (Tel: (01) 214-952-9494; Fax: (01) 214-952-9435); Energy Week Conference & Exhibition, Drilling and Production Economics, Houston (Tel: (01) 713 621-8833, Fax: (01) 713 963-6284; Louisiana Gulf Coast Oil Exposition, Jim Harrison, Lafayette, LA (Tel: (01) 3180295-6427; Fax: (01) 318-237-1030.
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