Giving Oil Rigs Legs



Imagine the engineering feat that would be required to move the Statue of Liberty even just a couple of yards.
While this might seem inconceivable, oil companies are doing something similar every day — they are moving drilling rigs that weigh more than Lady Liberty with nothing more than the push of a button. Modern “walking rigs,” as they are known, are onshore drilling rigs equipped with hydraulically powered legs or skidding systems. Weighing in at 500,000 lbs, Schramm’s T500XD, for example, is 11% heavier than the Statue of Liberty. Despite this, its platform is capable of lifting up and rotating 360 degrees, while the skidding system below walks to a new drilling spot.

Slow and Fast

Walking rigs are not called running or sprinting rigs for a reason — they move slowly. The T500XD, for example, moves at a rate of 30 feet per hour.
Neither can walking rigs walk very far: Patterson-UTI’s APEX WALKING rig can move up to 150 feet without the need to move primary equipment beside the rig itself.
One way to extend their range is by replacing conventional power cable festooning with newer cable spools such as IDS’ ReelRig. In fact, the need for greater lengths of cable is a key characteristic of walking rigs. Turtle & Hughes Texas offices work with walking rig engineers to help them meet their cabling requirements, making sure, for example, they use the type P marine cabling that meets the IEEE1580 standard for hazardous areas.
However, given that most onshore oil sites today employ pad drilling — where a number of horizontally-drilled wells are worked off a single pad, or collection of pads — the new drilling site may only be a few yards away.
So, despite their limited range, this makes walking rigs far quicker and more mobile than traditional drilling rigs, which can take weeks to dismantle and reassemble. Walking rigs can move to a new drilling site in a matter of hours.

Expensive but Efficient

Walking rigs are far more expensive than traditional onshore drilling rigs — they can be three times the price of the conventional rig. This, at first glance, makes it all the more surprising that the technology has come to prominence over the last few years during a period of depressed oil prices.
However, in an environment where oil prices remained consistently below $60 per barrel, oil companies have focused on becoming more efficient to make the most of the fewer dollars that they are receiving for their product.
Most of all, oil companies hate it when the oil stops flowing, and walking rigs cut the downtime when switching between wells to a minimum.
Similarly, they reduce the number of workers required for moving the rig, with the bulk of the work carried out by one operative sitting in the walking rig’s control room.
Walking rigs also cut the number of workers needed during operations. Schramm’s T500XD is equipped with a fully automated, hands-free pipe handling system, where drill pipe connections are made and broken automatically, rather than by oil rig workers using traditional hands-on methods. This improves both safety and efficiency (Schramm claims its walking rig requires 40% fewer workers than traditional rigs) and can save up to $1 million per 10-well pad. Carrizo Oil & Gas reportedly saved $15 million in eight months with a walking rig.

Recovery Rigs

Walking rigs have made slow and steady progress during the long period of depressed oil prices, and their march across the market looks set to continue.
Despite predicting that the onshore drilling market would in 2017 enter a period of growth after years of decline, Douglas Westwood’s World Land Drilling Rig Market Forecast 2016-2020 warns that neither the capable fleet size nor the number of operational rigs or rigs drilling is expected to reach 2014 levels by 2020.
Efficiency is likely to remain a watchword, with technology playing a central role.
Digital innovations and developments such as the Internet of Things (IoT) in particular must be embraced if the oil & gas industry is to thrive in coming years.
Covered in hundreds of sensors monitoring a myriad of processes, and relaying all of the data via satellite or Wi-Fi to central operations centers, walking rigs are well-equipped to be in lockstep with this digital revolution.
This modern technology on walking rigs is powered by a plethora of AC drives. More numerous but smaller and more compact than the large DC drives seen on older rigs, these AC drives make walking rigs far more electrically complicated than their predecessors, and Turtle & Hughes is on hand to help its clients navigate these intricacies, sourcing the equipment that works best together.

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