Drilling for answers

Casey McFann sits down with Dirk Montgomery, Director – Offshore Sales, MENA, National Oilwell Varco, to find out how drilling rigs come together

In the world of oil, drilling rigs are the essential tool of extraction. But what do we actually know about them? Dirk “The Driller” Montgomery explains the workings of today’s drilling rigs.

Dirk Montgomery, Director – Offshore Sales, MENA, National Oilwell Varco

Casey McFann: How does a drilling rig work?

Dirk Montgomery: In simple terms, the rig has five main components. They are the power system, mud system, rig structure, pressure control system and drill floor equipment. The power system supplies electrical power to the mud pumps, draw works, top drive, rotary table, shale shakers, mud agitators, blow out preventer controls and any other component on the rig that might require electrical power.

The rig is powered by generators that produce AC power. This power is then distributed to the various tools that require the power to operate in either a DC or an AC format. The mud pumps pump the mud from the mud tanks to the top drive, which is attached at the top to the travelling block and at the bottom to the drill pipe. The top drive rotates the drill pipe at a determined torque and rotations per minute (rpm) to cause the drill bit to penetrate the earth and form the well bore.

Has rig technology improved within the last few years?

Absolutely! Rigs have moved from being mainly powered by DC to being powered by AC. This typically gives the equipment more torque, power and longer lifetime of the motors as well as requires less maintenance on the motors. In addition, computerised tools driven by PLC’s (Programmable Logic Controllers) are being utilised on the rigs. Automation has been added to the pipe handling process via the use of iron roughnecks and automated pipe handling and pipe racking systems. This provides a safer work environment and requires fewer personnel on the drill floor, as there is less manual work being performed.

Add to this the new computerised drilling controls and control stations, and you have a safer, cleaner work environment for the rig personnel. The offshore marketplace has really embraced this type of technology and as is normally the case, the land marketplace is slowly but surely embracing it, as well.

What parts of the rig tend to go bad and need to be replaced most often?

This is subjective to the amount and type of preventative maintenance that is performed on the rig by the drill crew. A number of pieces of equipment require daily routine maintenance in order to keep operating efficiently. If this maintenance is not performed properly and/or routinely, any of this equipment will break down. Typically, the equipment with the most moving parts requires the most maintenance.

Where does the majority of rig equipment come from?

The majority of the rig equipment used to be manufactured in the United States. However, over the past 20 years many countries have begun manufacturing this equipment. National Oilwell Varco now has manufacturing facilities located in Mexico, Canada, Norway, Holland, United Arab Emirates, China and India, although the majority of our manufacturing is performed in the United States. Equipment is also being manufactured in Russia, Romania, Poland, Italy, Singapore and many other places that I can’t recall at this time. Suffice to say that the manufacture of rig equipment is a global effort.

Do rig operators need specialised training?

Yes. In addition to the “standard” training of learning how to operate a drilling rig, today’s rig crews require even more training in order to be able to operate and maintain the computerised equipment. Ironically, as the rig crews get younger, the computerisation training is required less due to their familiarity with computer games and equipment. In order to try to minimise this problem, National Oilwell Varco (NOV) has constructed and opened our first university in Houston, Texas, to train existing drilling crews on new equipment, new drilling personnel and new NOV field service personnel.

Is there a labour shortage or surplus regarding qualified personnel?

There is absolutely a shortage in today’s marketplace and this is expected to continue for some time. There are numerous new jack-up, semi-submersible and drillships being built at various shipyards around the world. Couple this with the large amount of land rigs being built and you have a serious labour shortage that has everyone in the oilfield scrambling to try and find personnel for their various requirements. It is not only the drilling companies that are seeing this shortage, but also the service companies.

VOCABULARY LESSON

Did you know it’s called a ‘drilling rig’, not an ‘oil rig’? Here are a few other terms you need to know:

DERRICK

The rig structure is commonly referred to as the derrick on offshore rigs and the mast on land rigs and then the substructure. The derrick or mast houses the top drive that is used in most of today’s modern rigs to provide drilling torque and rotations per minute (rpm) to the drill string as it rotates the drill bit in the well bore. In older rigs, this function is provided by the kelly and the rotary table, but it is much less efficient than the top drive. The substructure is the “base” of the rig and houses the rotary table, draw works, drill pipe tongs, driller’s control cabin (or station) mud manifold and numerous control panels.

DRAW WORKS

The draw works is essentially a hoisting device and operates like a block and tackle in conjunction with the crown block of the derrick and the travelling block that is suspended from the derrick with wire rope. The top drive is typically attached to the travelling block and the draw works will lower the travelling block/top drive as the drill pipe turns in the well bore, or it will hoist the travelling block/top drive in the event that a new connection needs to be made, or if the drill pipe needs to be removed from the well bore in order to change out the drill bit.

MUD PUMPS

The mud pumps provide pressurised mud to the top drive that then travels down through the drill pipe, out the drill bit through “jets” and then back up the hole and returns to the mud pits after being cleaned by the shale shakers. From the mud pits, the mud then re-circulates back down the well again via the mud pumps and returns back to the mud pits. The mud is used to cool the bit, clean debris from the well and to help offset any gas that might try to escape from the well bore. Depending on the formation that is being drilled in and the amount of gas that might be expected to be encountered, the mud will be “weighted up” by adding particulate matter to it.

BLOW OUT PREVENTER

The blow out preventer is located underneath the substructure and is used to close off the well bore to keep it from blowing out should gas under pressure be encountered. This is also where the weighted mud is typically utilised to help prevent the blow out. The choke and kill system, which is also a part of the pressure control system, is used to slowly bleed off or stabilise the well bore pressure so that a blow out does not occur. During this same procedure, the mud pumps are pumping the weighted mud into the well at a pre-determined rate to keep the gas pressure stabilised. This process is known as “pumping bottoms up” and is a somewhat delicate process. If it is not performed properly, a blow out could occur which could cause major damage to the rig and/or the well bore.

www.log.ae