The offshore market is becoming increasingly aware of the benefits that polymer products offer in some instances, says Serena Arif, director of PolyOil.
“The primary benefit is in terms of significant friction reduction (found to be a minimum of 22% in the field), but also the operational advantages due to their lightweight nature, improved safety in handling, excellent resistance to corrosion, and ease and speed of fitting,” she explains.
The lower coefficient of friction characteristic of polymers compared with that of steel (steel on steel in oil-based mud ranges from 0.2 to 0.25 while thermoplastic on steel ranges from 0.08 to 0.18) is of particular importance in ERD applications.
“While original cable clamps were designed for straight or slightly deviated wellbores inside casing, the advent of smart well monitoring and intelligent completions in horizontal reservoirs has necessitated a design shift,” explains Calum Whitelaw, PolyOil’s engineering director.
“(Polymer) cable protectors reflect these changing needs by ... providing centralization which is essential for horizontal or open-hole wells,” he says. “This centralization increases tubing stand-off, thereby minimizing the transition to tubular buckling, while also reducing friction during deployment.”
Example of a centralized & non-centralized control line protector designs.
Operations using shallow wells with long horizontal sections frequently encounter problems running tubing. This is often demonstrated in steel clamps which are prone to frictional drag and snagging.
An operator in the Qatar region recently ran a simulation prior to running tubing, and predicted a successful run to depth with 10,000 lb. to spare. This was simulated using a friction factor of 0.18 for the 9 5/8-in. casing and 0.23 for the 7-in. liner, data derived from a previous tubing run.
When the actual figures were inserted from this run, it resulted in friction factors of 0.16 for the 9 5/8-in. and 0.15 for the 7-in. liner. “Although some of this results from the trajectory of the well, it certainly appears that the plastic control line protectors aided in the running of this string,’’ says the operator spokesperson.
“The impact absorption of Poly-Tectors is better than steel,” says Whitelaw. “This means that any shock is dissipated more quickly, affording better protection to delicate fiber-optic control lines,” he explains. “Our clamps do not corrode either.”
The company’s control line protectors use a hinged arrangement for easy fitting to tubing at mid-joint or cross coupling positions. The lightweight design, typically one-third of a steel equivalent or better depending on designs, not only makes for easier and safer fitting, but also makes for a sleeker shape which is conducive to successful deployment.
Mid-Joint & Cross Coupling Protectors with control lines positioned in place, with view to interchangeability of slot configuration.
“The company’s Poly-Glider centralizers overcome axial friction and allow the transmission of torque by rotation, thereby reducing the constraints of torsion and buckling, and increasing the possibility of successful tubular deployment,” says Whitelaw.
PolyOil products also are used in the UK for well screen centralization when the well path is particularly tortuous. In August 2005, the company was granted a UK patent for its Poly-Tector. It has a patent pending for this product in Norway.
“Regular client feedback confirms that the Poly-Tector cable clamps and Poly-Glider centralizers continue to demonstrate the excellent material properties that the optimized design provides, as well as an outstanding protection system ensuring all control lines and cables are protected for the full length of the string,” says Arif.
The company recently won a $2.9 million (£1.5 million) contract to provide Poly-Tector cable clamps and Poly-Glider centralizers to the Al Shaheen field in block five, offshore Qatar.
