By Victor A. Schmidt, Special Correspondent
Reproduced in part for Vallourec USA Corporation with permission from The American Oil & Gas Reporter
Constructing a high quality wellbore from the pilot hole to target depth is dependent on a long list of technologies and processes, but none are more fundamental to success than the tubular components used to drill, case and ultimately produce the hydrocarbons. The performance metrics of pipe and connections continue to be redefined as operators drill evermore complex borehole architectures in the quest to develop tight oil, shale gas and deepwater reserves as efficiently, safely and cost effectively as possible.
In these demanding environments, tubulars and connections are subjected to increased torque, compression, fatigue, collapse, friction, drag, wear and other stresses, along with higher pressures/temperatures and more corrosive environments. And not only are today's well designs more challenging, but they also consume more tubular goods. With increasing lateral lengths, some onshore horizontal wells are rivaling their deepwater counterparts with respect to the total quantity of steel run down the hole. On average, a single horizontal or deepwater well requires enough pipe and connections to drill and case at least seven typical lower 48 vertical wells.
It is a different world out there with new sets of engineering and operating challenges, and oil country tubular goods manufacturers are responding with a new generation of solutions. The gold standard in OCTG and drilling tubulars has become high torque, high strength pipe and connections engineered to withstand the rigors of today's drilling and development programs, whether getting a 10,000 foot lateral to total depth in the Wolfcamp play or getting casing to bottom 25,000 feet below the mudline in a subsalt Miocene well.
Advanced Thread Design
Taking its place alongside the VAM® XForce drill pipe connection in Vallourec USA's catalog of solutions for horizontal wells is the VAM® HTTC™ casing connection, which Darren Santeler, technical sales manager, says is one of the company's top contenders for handling the extreme torque conditions in long lateral horizontal wells in shale plays.
"It uses an advanced thread design that has variable width for lock out and is cut with a dovetail cross-section that eliminates jump-out during make up and extreme loading," he explains. "The new thread design has two times the contact area of a conventional shouldered thread, providing an internal metal-to-metal seal for both internal and external pressure resistance." "The threaded and coupled connection is engineered specifically for high torque capacity and gas sealability to accommodate the conditions encountered in extended reach horizontals, including rotating casing strings while cementing in highly deviated and long laterals, as well as application such as drilling/reaming with casing," he goes on.
"The driver is torque," states Santeler. "With long laterals, the pipe rests on the bottom of the open hole, so rotation requires higher torque from the rig to move the pipe. The casing also has to resist high internal pressures for fracturing, which can crack standard API connections."
Santeler notes that the connection's high torque capacity goes hand in glove with the trend to larger 51⁄2inch diameter casing run from the intermediate casing down the length of the lateral. He notes that operators are setting 135⁄8inch conductor pipe, then running a 95⁄8inch intermediate string, followed by 51⁄2inch casing through the curve/build section all the way to the toe.
"Moving to a constant diameter of 51⁄2inch casing produces less waste, reduces cost and provides a higher frac pressure than using a 71⁄2inch casing string followed by a 41⁄2inch inch string for the lateral," Santeler says, noting that operators in the Eagle Ford are using primarily 23pound, 51⁄2inch casing, while Marcellus operators prefer 20pound, 51⁄2inch casing. "The grade of casing is a little different for each play, but the trend toward the 51⁄2inch high strength casing size is occurring across all shale plays."
Variable width dovetail thread connections come in standard (VAM® HTTC), semiflush (VAM® EDGE SF) and flush (VAM® HTF-NR) designs with "simple, reliable and easy running similar to standard premium connections," Santeler goes on. The connections are tested to the latest ISO and API standards for well assurance, as well as additional testing that mimics downhole bending, compression, tension, fatigue and fracture conditions to assure gas tightness. "The bending capacity is up to 42 degrees/100 feet and the full tolerance range of the product is tested," he concludes.
Contact us for more information on high torque connections for shale applications.