ADVANCED TECHNOLOGY

Seismic-while-drilling next step beyond resistivity, acoustics

Leonard LeBlanc
Houston

Halliburton's recently developed Scout Sonic LWD tool investigates a larger radius of the formation around the borehole than standard resistivity measurement.

Logging-while-drilling operations and acoustic sensing tools provide substantial information about formation structure, boundaries, and character immediately surrounding the borehole, but very little beyond five meters radial distance. Unfortunately, conventional surface seismic resolution, even 3D seismic, often cannot compensate for the lack of stratigraphic information adequately, especially on deep or subsalt wells.

Oil and gas companies have long pushed for a tool that better defines the formations at some distance from the borehole, without having to pull the drillstring to undertake well-to-well vertical seismic profiling or check shots to the surface. Two joint projects are underway currently to create technologies around seismic systems:

• Agip and Western Atlas are involved in the development of equipment and procedures using drillstring and bit noise sources with surface monitoring. Much of the project is confidential and no results have been announced.
• IKU (Norway) and Read Well Services are investigating both downhole sourcing and receiving processes, with complementary equipment on the seabed, for both drillpipe and coiled tubing. Also, development is underway on receivers that can handle strong vibrations and high temperatures downhole.

IKU has already developed a drillbit noise tracking system (Contrac) that provides a continuous borehole profile in three dimensions with drillbit position placed in a seismic map. The tool is accurate to five meters for every 2,000 meters vertical depth, regardless of measured distance.

Also, Halliburton has developed a full wave acoustic tool (Scout Sonic) to add to its LWD measurement systems. The acoustic instrument provides a profile of the formation at distances beyond that of conventional resistivity measurement (two-three meters radial distance).

Castable, weldable boron carbide can replace metals

A new material - more like metal than ceramic - could begin replacing metals on critical lightweight uses where strength and workability is needed. The material is boralyn - a boron carbide metal matrix composite - manufactured by Alyn Corporation of Costa Mesa, California. The material is already being used on vessel masts, propellers, anchors, archery arrows, skis, bicycle frames, and golf clubs. Boralyn is stiffer and lighter than aluminum, harder than steel, fracture resistant, and more predictable than carbon fiber or ceramic composites. The material is available in castable ingots and in extruded forms, and can be welded with metal welding equipment. Raw materials for boralyn - chiefly boron and carbon - are widely available.

Hydrates investigation underway in areas West of Scotland

Fearing that drilling off Western Scotland could disturb massive layers of sub-seafloor gas hydrates and create problems for shipping on the surface, the British Geological Society has been asked to investigate the existence of hydrates.

If released to the surface, gas hydrates can gasify and expand, displacing denser water volumes. The effect would be to substantially lessen the buoyancy of surface vessels above the rising gas. While that hazard seems real in theory, historically, no such events have been recorded.

At the same time, it is possible that a vessel could sink very quickly through a massive gas release, leaving no record behind. This has long been suspected as a cause of ship disappearances in the Western Atlantic north of the Bahamas Islands. In fact, the theory has been extended to airplanes flying overhead, which could lose power after the engines ingested large quantities of rising methane. That theory has not been proven either.

In any case, the Western Frontiers Association and the UK Health and Safety Executive would like to know, and to be able to inform drillers if such layers exist.

NKK develops laser welding for line pipe

NKK Corporation of Japan has developed a 25-kw laser welding system that can weld 10 mm line pipe at a rate of 10 meters/minute. The company is already using the process in orders involving carbon steel, alloy steel, and stainless steel line pipe with outside diameters up to 24 in.

Laser welding permits stable high speed welding without the production of X-rays, unlike electron beam welding.

The laser's energy may substitute for such fusion welding processes as tungsten inert gas and plasma welding, which produce high quality welds at low production rates. Laser welding produces finely distributed oxides, which keep heat-affected zones from deteriorating, a problem in fusion welding.

Long distance subsea electrical power transmission sought

Petrobras and Siemens (Germany) are jointly developing a method of transmitting electrical power in deepwater over long distances sufficient to power submerged centrifugal pumps. With this equipment, the Brazilian oil company will be able to produce many deepwater fields subsea from facilities located in shallower water.

In theory, the system would work as follows: Equipment aboard a shallow water platform would generate power, then run it through a frequency inverter and a transformer. After transiting distances of as much as 35 km, another transformer would convert the current at the wellhead, and send it to the pump. A system at the seabed transformer would circulate oil within to compensate for the external pressure.

Deployment of the first test system is scheduled for December of this year. The Carabepa-3 platform will generate the power.

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