Innovative dopeless technology eliminates the need for thread compound and all its associated disadvantages.

All operators face the challenge of maintaining low finding and development costs with increasingly complex drilling conditions. Technologies that can reduce risk and operational costs, or increase efficiency levels while maintaining the highest standard in QHSE, will continue to grow as requirements for both profitability and regulatory compliance increase. In many cases, improvements in QHSE performance and compliance can also bring levels of improved efficiency and reduced costs, bringing tangible value to the overall operational results.

One of the areas where operators can reduce costs, increase efficiency, safeguard their production and improve environmental compliance is thread doping on casing and tubing strings. For years, the use of thread compound, or pipe dope, has been a "necessary evil" to prevent both galling and corrosion to ensure a tight seal on connections. So for providers of tubular goods the idea of eliminating the need for thread compound, and thereby reducing its detrimental effects on the environment and on operational performance, represented both a challenge and an opportunity.

The challenge was to find effective alternatives that provided the lubrication functions traditionally performed by thread compounds. The opportunity was to create a reliable dopeless technology that would result in cost savings as well as environmental and increased operational benefits. Extensive studies, coupled with a Tenaris' active commitment to research and development in the areas of corrosion, metallurgy and connection design, as well as a broad analysis of compounds, materials, and surface and finish treatments, resulted in the development of the first commercial dopeless connection technology successfully run and available to the worldwide petroleum market.

Dopeless technology imposes other challenges that must be considered and researched. Compatibility with various tubular coatings, as well as with both well fluids and some of the more aggressive and corrosive completion fluids must be well understood. A successful dopeless technology must include important considerations related to premium connection design. Connection design must include the optimization of many parameters such as thread pitch and taper, thread profiles, seal geometry, interferences and contact pressures, and the minimization of the sliding distance in all areas of contact.

By eliminating the use of thread compound from running operations, operators avoid environmental problems of thread compound disposal and costs, but also improve efficiency and reduce the risks associated with its usage. Among its positive effects, a dopeless-connection technology provides:

• Reduced preparation time and costs associated with onshore and offshore cleaning and inspection procedures;
• Efficient and faster makeup during tubular running operations;
• Increased personnel safety with reduced rig floor handling and less exposure to petroleum-base dope;
• Improved safety and environmental compliance derived from cleaner drilling floors and work areas;
• Reduced rig costs for tubular cleanouts prior to completions with the prevention of skin buildup due to formation contamination;
• Avoidance of mud contamination;
• Reduced risk of downhole tool malfunctions: downhole valves, sliding sleeves, caliper devices, pressure and ultrasonic sensors, tractors, logging tools;
• Positive environmental benefits; and
• Lower thread compound disposal costs.

Challenging thread compound

The dopeless connection provides a viable alternative to thread compound's three basic functions:
Sealing. Traditionally, casing and tubing connections employ petroleum-base dope, often containing additives such as copper and graphite, to form a seal against liquids and gases.

A dopeless connection must be able to maintain seal integrity via a metal-to-metal seal under all designed loading conditions, without the benefit of any sealing effects created by thread compounds. Under high-temperature testing, where typical thread compounds dissipate (354°F or 180°C), the TenarisBlue Dopeless connection has maintained a seal underthe most stringent of ISO 13679 CAL IV loading conditions.

Lubrication. Usually, during make-up and break-out operations, frequent lubrication is the sole alternative to prevent galling caused by the friction between thread and seal surfaces under heavy pressure from the weight of the joint being made up and high torque from the tongs. The solution developed by Tenaris requires only a single application of dry surface coating at the mill that enables the connection to withstand multiple make-and-break operations without additional lubrication.

Corrosion protection. Long before casing and tubing joints see their first day of service, they are subjected to transit times of up to 60 days and then storage periods that can last for months. Generally, operators request application of storage dope on the pin and coupling to avoid the corrosion damage resulting from extended exposure to water, oxygen, salt and other corrosive agents. The dopeless connection allows for efficiencies with reductions in pre-job preparation cost by reducing, and in most cases eliminating the need for the removal of storage compounds. Threads can be easily inspected prior to shipment, and arrive at the rig ready for use without subsequent preparation.

Improving operations efficiency

Because thread dope has been used for so long, many operators do not consider the significant amount of time consumed by the use of, or the problems associated with, these compounds. The dopeless connection improves efficiency and reduces operational risks at the rig by eliminating dope application before running. Most importantly, it also reduces problems caused by inconsistent dope applications or by contaminated dope that can cause thread galling; dope contaminated with sand, rust or other debris is a common problem for operators. To date, excellent results have been achieved for various operators in the North Sea, Middle East and South America.

A dopeless operation:

• Improves sand and silt screening systems efficiency, by eliminating clogging or plugging problems with sand-control screens contaminated by pipe dope.

• Avoids problems with completion mechanical devices. With no dope, there is less chance for grease and dirt buildup to interfere with valve seals or sliding sleeves.

• Reduces formation damage and improves cementing quality. No excess pipe dope will be carried downhole by kill fluid, injection fluid or cement slurry. The absence of dope, dirt, rust and petroleum-base aterials avoids the risk of clogging perforations with compound and/or formation skin damage, thus reducing the risk of losing production or incurring the costs for unnecessary acid treatments.

• Eliminates cementing problems caused by dope on the outside of the casing. Current pre-flushes and washes used in cementing to remove drilling fluid are not powerful enough nor were they designed to remove viscous pipe dope clinging to the casing or smeared on the wall of the annulus. The pipe dope, if left in the annulus, could inhibit zonal isolation, the primary purpose of cementing. Pipe dope left on the outside of the casing will also cause formation damage, if it comes in contact with the target zone strata.
• The preparation time for casing and tubing is dramatically reduced or eliminated prior to rig use. The estimated time saved in not having to clean and dry and dope threads prior to use ranges from 5 to 15 minutes per joint, depending on the type of thread compound and the size of the joints. In a well of 250 joints, the savings can range from 20 to 60 hours in preparation time alone.

Conclusion

The growing need to address the environmental and operational challenges of increasingly complex and more expensive drilling and completion operations is forcing oil and gas companies to seek new technologies to replace outdated and less cost-effective procedures. Additional research by the industry will be necessaryto meet the present and future challenges now required by governmental regulations and corporate HSE compliance standards. By eliminating heavy, metal-bearing, petroleum-base dopes from drilling and completion operations, the dopeless connection solution provides oil and gas companies with an innovative technology that will enable them to improve overall performance and efficiency by attaining better use of their working capital. It also achieves overall operational cost reductions while enhancing their environmental compliance.

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