By: Scott Osburn, Nabors Well Services
Accelerated drilling in the oilfield has triggered a marked upturn in demand for well site services industry wide. Looking to achieve higher profit margins, the well servicing customers of today are in the market for equipment incorporating advanced technology, compact but powerful features, faster components, enhanced safety elements, accurate electronic instrumentation, greater power distribution and better control.
In 2005, Nabors Well Services set out to build just such a swab rig.
Nabors Well Services partnered with Canadian-based Care Industries, Ltd. to create a rig with contemporary design and four goals: (1) consider the environment where the swab rig will work; ( 2) research and choose a truck chassis that is compatible with the area or fleet; (3) comply with all Department of Transportation (DOT) requirements; and (4) meet and/or exceed all customer safety rules and regulations. The finished product was a state-of-the-art rig that is safe, efficient and cost effective.
The new Nabors Well Services’ swab rig is ideal for pulling fluid from producing wells. Swab rigs are particularly effective in free flowing coal bed methane wells and in other wells where fluid build-up is common. These fluids may be naturally occurring from formation seepage or be the result of kill fluids that were previously pumped downhole. Once fluid from these wells is removed, production returns to normal levels.
The swab rig is built on a Mack CV 713 truck chassis, with a truck mounted machinery deck consisting of the sandline drawworks, mast and operator’s cabin. The powertrain consists of a 350 hp Mack Aset diesel engine coupled with a heavy duty Allison 4500 series transmission. Power is directed to either the sandline drawworks or the tandem drive axles through the Spicer Model 784 Transfer Case. The sandline drawworks houses 16,000 feet of 9/16″ regular lay sandline, and uses 42″ x 8″ brake flanges. A mechanical brake lever in the operator’s cabin controls the brakes through a series of bellcranks and push-pull tubes to assure the “feel” of the system. An air actuated parking brake is included for safety. The drawworks is fully enclosed to prevent personnel from being trapped and/or injured in the drum.
The 48 foot mast is rated at 35,000 pounds single line pull and is designed, manufactured and monogrammed per API specification 4F. It is hydraulically operated, is free standing and does not require guylines, thus reducing the time required for rig up and rig down. The hydraulics control station is located next to the mast base and operates the leveling jacks, mast raising rams and winch line. Crew comfort and protection is imperative for safe, efficient operation. The all-aluminum operator’s cabin is climate controlled and replaces the outdoor operator’s station on older swab rigs. Crews are no longer subjected to the heat, wind, rain and cold or the dangers of standing next to the drawworks. A power inverter in the operator’s cabin provides power for the air conditioning unit and additional power for a computer, microwave, and the like.
These additional elements in the new Nabors swab rig make it safe and less expensive to operate:
• Lightweight composite walkways/ handrails that fold for traveling and increase the speed of rig up and rig down
• Anti-lock braking system for safer roading
• A transfer case that transitions from the roading mode to the drawworks mode simply by throwing a lever in the driver’s cab
• Fast actuating hydraulic leveling jacks
• Lights for night swabbing operations when required
• Ergonomically located operator’s controls
• A variety of cup types and mandrel sizes to perform the job at hand Once rigged up, all swabbing operations are conducted from the operator’s cabin. The operator’s control panel is ergonomically designed and allows the operator to control and monitor the powertrain and drawworks.
Here is where the integrated depthometer makes its mark. It provides a digital readout of the sandline depth, sandline speed and weight indicator. Typically, crews do not know their speed or weight, relying heavily on a line counter for sandline depth. Customers may know what is in the well, but crews can never be 100 percent certain of well conditions. Prior to the depthometer, the only indicators the crew had were the shock waves from the tool tagging the fluid and the slack in the line to determine fluid levels. The depthometer gives the operator an additional signal the fluid has been tagged by a noticeable reduction in load on the weight indicator. Crews no longer have to rely solely on the “feel” of the rig during operations. The depthometer also provides the customer with an accurate location of tools, such as packers and plugs, that have been placed downhole.
The new Nabors swab rigs are extremely mobile, and many swabbing operations require less than an hour to complete. Rig up and rig down time is minimized, resulting in a significant savings for customers. The time saved allows the swab rig to service multiple wells per day, and helps the customer increase profitability by limiting the downtime of their wells. The inclusion of digital instrumentation ensures accurate servicing information can be delivered to the customer if requested. The swab rig was designed with safety first and foremost in mind. Most customers find that this state-of-the-art piece of equipment also reduces cost and enhances the bottom line. Nabors Well Services launched the new swab rig into service in October 2006. Currently, these swab rigs are working in Oklahoma, Texas and Wyoming. Nabors plans to introduce more swab rigs into the fleet by the end of 2007.