As air drilling becomes more specialized, both drilling contractors and system suppliers are working to customize their offerings
Air drilling is a fine art. Using compressed air or nitrogen to cool drill bits and lift cuttings from the wellbore often works faster than drilling with liquids. Flexibility of operations combined with reliability of equipment and operators is the key to meeting clients’ needs as industry activity continues to ramp up, says Don Wells, president of Air Drilling Associates, Inc.
The air drilling contracting company has headquarters in Farmington, New Mexico, and was founded in 2002 with an emphasis on oil and gas resource development in the western hemisphere and on geothermal drilling from its operations in Jakarta, Indonesia. The company also operates in Canada, Iceland, the Philippines, New Zealand and New Guinea.
Air Drilling Associates maintains a stock of 150 compressors and boosters in addition to ancillary equipment such as mist pumps and membrane nitrogen generators by National. The compressors are represented by two main vendors, Sullair Corporation and Atlas Copco and are largely powered by off-the-shelf diesel engines from Caterpillar Inc. and Cummins Inc. The compressors are helical screw models, which launch air at pressures ranging from 365 to 500 psi.
The reciprocating booster compressors (piston-type), are supplied by packaging manufacturers such as Gardner Denver/Joy with Cummins and Caterpillar engines again supplying power. The boosters take the air pressure to the next step in stages, often as high as 5,000 psi. Rotating head controls are from Washington and Elite Energy.
Air drilling techniques range from dry air (dust), mist, foam, aerated fluid and other underbalanced techniques for petroleum and geothermal projects. Other compressed-air critical functions include: aerated fluids drilling with air, natural gas, or nitrogen; coal bed methane cavitation; pipeline dewatering, evacuation, pressure testing and commissioning; and air, natural gas and nitrogen pressure testing of process facilities.
FAST AND EFFICIENT
“For us, a variable range of pressures and volumes available is one of the most important features in our equipment,” says Wells. “When companies specify air drilling, they’re doing it for one reason—to drill faster and more efficiently. We’re looking for controls that can give us anything from high volume at low pressure for typical air drilling, to low volume at high pressure to meet the needs of our clients.”
The highest pressures are reserved for such operations as parasite string injection drilling in the shale plays in the Piceance Basin in Colorado. The process is an alternative to conventional drill string injection and involves running small-diameter tubing on the outside of the intermediate casing to a pre-determined depth, where it is ported into the wellbore. The gas is then injected through the tubing and into the wellbore.
“The depth of the injection port is determined by the maximum pressure reduction anticipated to avoid lost circulation,” says Dennis Wood, business development manager with Air Drilling Associates. “As you drill deeper using aerated mud, the friction gets pretty high, and these applications can take pressure up to 5,000 psi.”
The company’s compressors weigh from 15,000 to 23,000 pounds, with boosters weighing in from 33,000 to 45,000 pounds each. A compact footprint is important. The assemblies must be small enough to drive down a highway, two compressors to a flatbed truckload. They also need to be moved at a moment’s notice.
“Some of the well drilling projects we’re involved in give us some lead time, but often we’re called two or three days before drilling is set to begin, so mobility is important,” says Wells.
CRITICAL INSPECTIONS
The first order of business with each client is modeling of the wellbore configuration. The company examines the site layout and determines the best location for the compressors, based on a combination of site logistics and ergonomics.
“We need access to water and obviously to the main connection at the drill rig,” says Wood. “That’s all pressure piping, so there’s no on-site welding or cutting on those lines. The land under the compressor needs to be leveled, or the equipment is placed on a wood-and-metal frame to achieve the same result. We also lay down membranes for environmental protection.
“We’re typically required to do a lot of leveling and prep work in the Pennsylvania shale plays,” Wood continues. “The equipment undergoes a lot of movement and transport, so it’s essential to inspect the machinery, particularly the couplings, before starting them up.”
The company’s air compression packages are standardized as much as possible, not only to ensure that equipment is easy to operate, but also to allow for ready replacement of inter-compatible components. Components are chosen from suppliers with extensive global parts and service networks to help ensure uninterrupted operation at remote sites.
The units are stocked with abundant spare parts, including belts, filters, sensors, starters, alternators and batteries. The entire compressor fleet averages three years old. As older equipment loses reliability, the units are systematically re-manufactured to meet like-new specifications.
Environmental and safety regulations are becoming increasingly critical in compressor operations around the world. The company conforms to the latest ISO 14001 environmental standard and ISO 18001 Occupational Health and Safety Advisory Services standard.
The newest compressors are powered by engines manufactured to Tier 4 U.S. Environmental Protection Agency emissions standards. “In 2012, the only place Tier 4 kicks in is California,” says Wells. Regulations regarding excess noise are also increasingly important, with diesel mufflers fitted with sound attenuation equipment. The mufflers also have spark arrestors built into them, improving safety in gas and oil fields.
DRILLING CHEMICALS
Drilling foams and agents are also becoming increasingly specialized, offering benefits ranging from the recyclability of the foam, to its ability to inhibit corrosion or withstand either drilling-related heat or climatic temperature extremes. The company manufactures its own line of drilling fluids formulated to its specifications.
“You need to know what’s available on the chemical market to offer the widest range of services,” says Wood.
Once drilling begins, open communication between the air compressor operator and the drill rig is crucial to provide compressed air on demand to ensure borehole walls remain stable and to control the entry of fluid into the wellbore. Each air compression rig is usually accompanied by two operators who spell each other in 12-hour shifts.
Digital monitors record the air volumes and pressures to ensure that the compressors have delivered exactly what was ordered to the drill rig, while increasingly sophisticated sensors assist in troubleshooting equipment.
Although air drilling operations often emphasize technology, safe and successful operation of the equipment requires thorough operator training to manufacturer specifications.
“Training directly increases the longevity of the machinery,” says Wood. “Our strength is the competent and mechanically-inclined people who operate this equipment in the field.”
AIR DRILLING: THE SUPPLY SIDE
As oil and gas drillers become increasingly specialized, drilling contractors are demanding compressor systems customized to their needs, says Pran Kirtani, sales and project manager with National Compressed Air Canada Ltd. in Mississauga, Ontario, Canada. The company has developed, manufactured, and serviced compressors and drilling equipment for more than 40 years.
Land-based seismic exploration is typically carried out in remote locations, so contractors are demanding lightweight compressors and drilling equipment used to drill vertical shot holes. The holes are loaded with explosives and detonated in a precisely controlled sequence while geophones read the rebound energy from the detonation and the data is processed to search for the presence of hydrocarbons.
“For remote locations, we provide a range of man-portable, helicopter-portable and carrier-mounted compressors and drilling equipment used in various parts of the world for shot hole drilling,” says Kirtani.
Modular man-portable compressors are built so that each module can be carried by human power alone and assembled into a working compressor.
For production, the company supplies a range of high-pressure, two-stage rotary screw air compressors up to 500 psig and a range of high-pressure air and nitrogen booster compressors to 5,000 psig used in various oil and gas drilling applications.
VERSATILE PERFORMANCE
“Versatility of the units is the key here,” says Kirtani. “That’s particularly true for oil and gas drillers who want to use those compressors not only for air drilling, but a range of applications such as pipeline testing, or to power other pneumatic instruments on site.”
Severe weather packages must operate reliably at a temperature range of between -40 and 122 degrees F. “These compressors are typically taken thousands of miles in a single year,” notes Kirtani. “It’s possible to have them used in extreme environments on both ends of the weather spectrum during a short period of time.”
The company also provides extensive training for air compressor operators and engineers. Training ranges from in-factory sessions to explain how systems are designed, to on-site training and troubleshooting instructions.
“The packages are designed for easy user serviceability, maintenance and operation, but we stress that with these customized packages, training is key,” says Kirtani. “The operator simply can’t jump from one compressor system to another without appropriate training for each customized compressor setup.”
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