Advanced technology and
high performance for shale
A challenge has been set. For unconventional Oil & Gas formations (such as shale) to be competitive on the global market, operators
now demand that OCTG premium connection manufacturers address longer laterals, increased torque requirements, higher load limits,
and enhanced fatigue performance while still being cost effective. Vallourec has responded to this challenge with an array of VAM® premium connections to address the shale operator’s specific concerns.
Unconventional Well Designs
Horizontal drilling and hydraulic fracturing techniques have made shale hydrocarbons accessible. The well designs for these unconventional shale formations typically consist of 13 ⅝” surface casing, 9 ⅝” surface casing, 7 ⅝” inter-mediate casing in some regions, and 4 ½ – 5 ½” production casing. The wells have a vertical section dependent on resource depth followed recently increasing horizontal section. Some horizontal sections are approaching 15,000 ft or even more! The build rate in the curve is generally targeted at 10°/100 ft, with the actual build usually peaking at a max of 20°/100 ft.
Operators have determined that API connections, while offering tension and pressure capability, are insufficient for handling dynamic loading, torque, and bending. The well designs for these horizontal wells require the pipe and connection be exposed to high torque, bending, compression and tension loading, pressure cycling fatigue during the fracturing, all followed by a production phase. It has been documented in technical industry publications that API connections, as well as incorrectly selected premium connections, have failed to meet the constraints of these applications.
One of the main challenges in horizontal or Extended Reach Drilling (ERD) is the drag friction force. This is due to the string weight during its deployment in the deviated and horizontal well bore sections. In order to cope with this friction to reach total depth, one technical solution employed by the operators is rotating the string to bottom. The longer the horizontal lateral encountered, the higher the torque requirement to overcome the increased friction. In addition, increased torque aids in improving the cementing quality, by rotating during the cementation phase. As high torques are requested on ERD for many of the same reasons, the pipe and connections need to withstand the high torque while maintaining the connection’s mechanical and sealability performance.
VAM® Connection Applications
When an intermediate casing string is required for a stable well bore, operators have successfully used VAM® HTF-NR. VAM® HTF-NR is a great solution for this application as it is a flush premium connection with two metal to metal seals. A dovetail thread design gives it high torque while, providing maximum clearance for slim hole wells.
For the production casing, a semi-flush connection is often used in the bend and the lateral section of the well. Many operators prefer to use integral connections in the bend and in the lateral, due to the slim OD profile providing an easier installation process. The smooth OD profile of integral connections allows the string to easily slide into the lateral section due to reduced contact with the well bore. In turn, less torque is required which reduces the reciprocating axial load and minimizes the chances of the pipe getting stuck.
Sometimes the demand is to have a single solution for the full string length that can be run both in the vertical and horizontal portions of the well. VAM® is able to cater to this requirement by offering the VAM® EDGE SF connection. VAM® EDGE SF is a gas tight semi-flush premium connection with a high tension rating and extreme high torque capability. This makes it ideal to run as complete production casing in shale wells with extended horizontal sections.
A stronger connection may be required in the vertical portion of the well to achieve tension loads caused by the weight of the string and compression loads from the setting down weight during installation. In some shale formations a threaded and coupled (T&C) solution is required in order to have a connection that is as strong as the pipe body while providing the operator with necessary safety factors for tension and compression loads. The same high torque requirements exist for T&C connections in the unconventional formations. In conditions where high torque is required with only liquid sealability, such as for shale oil wells, Vallourec offers the DWC/C semi-premium connection series. DWC/C is the economical T&C solution for high torque and when well conditions are not as severe. Where high torque and gas sealability is required, the VAM® 21 HT premium connection offers performance ratings as strong as the pipe body while operating at its Maximum Torque with Sealability (MTS). VAM® HTTC is the ultimate T&C solution for extending extreme torque limits to enable the rotation of the string through the bend and into the long horizontal section. VAM® HTTC keeps its full performance ratings even at it’s MTS.
Vallourec connection comparison for unconventional Oil & Gas
High Torque and Extreme Connection Flexibility and Adaptability
Operators in the unconventional Oil & Gas formations require that operations be flexible and adaptable. With the VAM® connection portfolio, operators can respond to market fluctuations that are found with fracturing (frac) operations. It is common for frac operation costs to rise proportionally with the increase of frac pressure. To increase frac fluid volume on a smaller ID tubular, the fluid must flow faster or at higher pressure. A small OD tubular will require higher frac pressures than a larger OD tubular and will usually require a higher frac operation cost. The opposite would be true for a large OD tubular. An operator can have the flexibility to switch from a 4 1/2” 15.10# tubular with a T&C connection to a 5 1/2” 23# tubular with a semi-flush connection in order to reduce frac pressure, and thus cost. Operators are also looking to optimize the well designs to be more efficient. For example, 6″ 24.1# pipe is becoming a trend in shale operations and Vallourec has pioneered this adaptation through the expansion of the VAM® 21 HT/ DWC/C products in that specific size and others. VAM® accommodates flexibility by having several high torque integral and T&C connection options.
Well Integrity With Fit-For-Purpose Testing
Reliability is essential in unconventional play operations. Operators require connections that are dependable throughout the life of the well. Many of the VAM® connections have endured a fit-for-purpose test program based on the latest international standards (API RP 5C5) or more extreme testing. As fracturing technology evolves, connections are being subjected to higher frac pressures, and a greater number of high-density frac stages. Fatigue is also a major consideration, particularly if the string is rotated during cementing. A connection may be submitted to as many as 100,000 cycles in the dogleg section of the well during the installation. VAM® ’s fit-for purpose tests have focused on simulating the rotation of the string and multiple severe frac cycles, followed by the combined loads that would be encountered during the gas production cycle. For example, VAM® EDGE SF was successfully qualified through fatigue testing followed by two frac tests which focused on 20 high pressure liquid cycles combined with high tension. The fatigued connection then successfully passed a gas sealability test following the API RP 5C5: 2017 CAL II qualification procedure. In specific cases, more reliability and sealability performance is required. VAM® has addressed this by qualifying the VAM® HTTC connection to the latest and most severe industry standard, API RP 5C5: 2017 CAL IV.
Vallourec brings higher performance solutions to unconventional plays at competitive pricing
Vallourec has responded and is continuing to meet the challenges of the unconventional Oil & Gas formations by offering a full suite of connections that have been specifically designed for the unique demands, economics, and performance requirements that are encountered in the shale plays. VAM® connections are ensuring that operators are able to push the boundaries of these unconventional developments.