Rig sets pace for mobile drilling

About 75 invited visitors from drilling contractors, oil companies and equipment manufacturers were given a demonstration last week as the new rig dubbed LOC 250 was put through its pipe-handling paces at the company's Schiedam yard near Rotterdam.

The rig derives its name from the phrase "land and offshore containerised" along with its Tesco topdrive's capability of exerting a pull of up to 250 short tons on the drillpipe or casing string hanging off it. The company is already looking at moving up to 500 short tons.

The rig is completely self-erecting, needing just three trucks and no cranes for this task. Once final teething problems have been ironed out, the present prototype will undergo a test dismantle and 50-metre move in the yard.

In normal circumstances, Huisman claims that such a move will be possible in about 24 hours from the start of dismantling at one location to ready-to-drill at the next.

However, for this first exercise, "we'll be happy if we carry it out in a few days", said Leopold van den Assum, the company's project manager for the development.

Before the end of the year, the rig will be shipped to Texas for its first commercial operation, in the hands of development partner Fidelity E&P, drilling onshore for stranded gas. It has fully hands-off automated pipe handling, capable of dealing with both casing and drillpipe.

"The market is very conservative in applying new technology, so we first have to prove it in the oilfield." said van den Assum. If demand builds encouragingly "we think it could be feasible to build up to three rigs per year". Offshore applications would follow later.

One the rig's main marketing strengths is its transportability. "This is the first rig that can be broken down into pieces that are of standard ISO container size, accepted around the world for shipment by rail, truck or ship," said van den Assum. It divides into 17 packages, weighing from 25 to 36 tonnes.

This should give it an edge everywhere where transportation of heavy units is difficult, he said.

Conventional rig moves can involve elements weighing 100 tonnes, leading to complications with bridges unable to take these loads, and time-consuming paperwork associated with special permits needed for overweight and oversize movements. "Our rig has the advantage of a very small mobilisation cost."

Second, van den Assum pointed to the rig's fully integrated control system, covering all components from the various suppliers, where normally each of these might have its own individual system.

Another major feature of LOC 250 is that it is designed for both conventional drilling using drillpipe, and also for the emerging technique of casing while drilling, using the same automated pipe-handling processes.

Casing drilling is improving the economics of exploiting ever-smaller pockets of reserves, and the new rig from Huisman-Itrec has been evolved in a joint venture with Drillmar, a specialist in non-traditional drilling technologies.

Instead of using drillpipe to drive the drillbit, it is latched to the bottom joint of standard oilfield casing and this whole string is rotated.

Advocates of the technique claim that a casing-drilled well can be built in as little as half the time needed for the conventional approach, with all the cost savings this implies, and with far less risk to well integrity.

The LOC 250 is rated for 15,000 feet of seven-inch casing or 12,000 feet of 4-1/2 inch drillpipe.