38 Oil & Gas Product News March/April 2014 www.oilandgasproductnews.ca

T he demands on equipment in the oil and gas industry in-crease year over year as higher pressures and temperatures

are reached in new production methods. When designing components for these applications, material selection and design processes become critical in the overall success of the tool and production system. These demands are expected for equipment lifespans that may be 10 to 20 years in extreme environments and where sensitive electrical and data transmission is vital to success, especially in newer intelligent measurement while drilling (MWD), logging while drilling (LWD), and wireline systems. This type of per-formance rating often exceeds the overall capabilities of materials such as thermo-sets, aluminum, steel, and titanium.

Using PEEK (part of the PAEK (pol-yaryletherketone) family of thermoplastic polymers) in place of these or lower grade plastics, industry challenges can be easily met. (For example, VICTREX PEEK 450G exceeds NORSOK M710

2S concentration 10x the required performance standard). According to VICTREX Polymer Solu-tions, PEEK exhibits superior chemical resistance to both metals and thermosets which can reduce downtime and increase the lifetime of installations when corro-sion and chemical attack would normally cause a failure. The properties, advan-tages and potential of PEEK polymers in many applications have been documented and tested for more than 35 years.

The future trends of the industry further amplify the need for PEEK-based composites in unconventional drilling and formation evaluation, where applications such as high-performance antennae and logging sleeves are found. Mechanical and hydraulic-actuated sleeves operate

at high temperatures where PEEK-based composites have excellent performance and long life in use compared to ther-mosets. These composites have many

-als, including high strength and stiffness along with very light weight (40 percent lighter than aluminum, 55 percent lighter than titanium and 70 percent lighter than steel) which can facilitate easier

turnaround. Also, extremely low thermal expansion (as low as 1/6 that of steel), the ability to tailor this expansion rate, and dimensional stability allow for precision manufacturing to tighter tolerances.

-er reinforced plastic composite structures, often because of their high electrical resistivity or low electromagnetic radia-tion interference. Thermoset and thermo-plastic based composites are commer-cially available, and each material brings

general, thermoset composites and some commodity level thermoplastics offer a

for less extreme environments. On the other end of the spectrum, engineering grade thermoplastics such as PEEK are used in high pressure/high temperature (HP/HT) applications or other environ-ments requiring materials with outstand-ing chemical resistance. These resins tend to have higher initial costs and survive longer than thermosets in HP/HT ap-plications. In addition to the resin choice,

-ture and corresponding manufacturing options. For instance, performance varies widely between continuous and chopped

-tion vs. compression molded structures, a performance difference can be evident in service.

is essentially characterized by several

microns in diameter, evenly distributed and encased in a resin. This spooled raw material is delivered to the manufacturer in the form of a tape (Figure 1).

Fiber placement technology such as that developed by Automated Dynamics allows thermoplastic composite structures to be built up, strip by strip, layer by

This in-situ automated process melts and freezes the resin on a strip of tape and bonds it to the previous layer (Figure 2). This streamlined processing has many advantages over oven- or autoclave-cured thermoset resins. Those associated with part performance include: extremely re-

-ling associated with de-bulking thermo-sets during cure cycle, and avoiding high

thermal induced residual stresses that can come with a long-soak cure cycle.

The more demanding of these down-hole applications often require con-

because of their higher modulus and

composites. These applications include antenna shields on various measurement technologies on LWD tools, electrical/structural isolators (gap subs) on M/LWD (measurement/logging while drilling) and wireline resistivity tools, and housings and logging sleeves for wireline resistiv-ity tools. In pressure-balanced loading scenarios, PEEK based structures are used upwards of 525 degrees F (274 de-grees C) in wet conditions. In other cases

force over extended lengths of time, PEEK composites are routinely used from 275 degrees F (135 degrees C) to

Composites meet high performance demands for unconventional drilling and formation evaluation applicationsby Brett Kimball and Rich Leibfried

Figure 1: Fiber composite material in tape form.

Figure 2: Fiber placement technology.

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40 Oil & Gas Product News March/April 2014 www.oilandgasproductnews.ca

350 degrees F (177 degrees C), traversing the glass-transition temperature of PEEK.

These applications tend to require ma-terials that have high damage tolerance and resist chemical attack, fatigue, and creep. While PEEK composites exhibit excellent properties in these areas, under-standing their failure modes in contrast with metallic structures is critical. For example, composites exhibit little to no plastic yielding leading up to failure, with no graceful strain like ductile metals. Therefore, safety factors in composites design tend to be much lower than those in metal designs.

PEEK-based composites offer sig-

thermoset based composites based on an excellent combination of properties including hydrolytic stability. While PEEK composite absorbs around 0.2 percent moisture, thermosets often absorb 10 times this amount, which leads to dimensional instability and accelerates crack propagation.

Designers usually need to interface these composite structures with metal-lic components, and be aware of their inherently different material properties. The biggest difference between met-als and continuously reinforced plastics is that their highly anisotropic nature-

volume, has tensile strength of 300ksi

12ksi (83MPa) in the transverse direction. Furthermore, designers must know the

the structure, not just the tape or material-level properties. Such details may require the designer to have knowledge of the material’s machinability, moisture uptake, failure modes,and mechanical, electrical, and thermal properties.

A complicated design usually entails collaboration between the tool designer and manufacturer, and most composites manufactures employ composites engi-neers to facilitate this collaboration. In addition to material properties, there are manufacturing-induced aspects that must be accounted for, and some that can be taken exploited. For instance, when over-wrapping a metallic cylinder, a very tight compression can be achieved through

chilling the substrate during manufac-turing. Fiber placement also allows a

to match an adjacent metal structure) by altering the angle individual plies are stacked.

In addition to assembling dissimi-lar materials, designers can often join them. PEEK-based structures are suited

design of a metal-to-composite interface. This thermoplastic is used in the compos-ite tape, and can also be bonded to metal

-ite and metal tubulars (Figure 3). Coating with VICOTE, a PEEK-based coating from Victrex, helps bond the materials to transfer force between them, and to

Automated Dynamics has delivered

parts for several applications using this

placement manufacturing in the joint’s design.

Taking advantage of these materials and manufacturing capabilities allows for their use in many downhole and subsea applications, including composite components for seals, completions tools, pressure vessels, structural frames, motor housings, production tubing, and more. Automated Dynamics has developed a

-cantly increase manufacturing through-put. This high throughput is critical for large scale projects requiring hundreds or thousands of pounds per part. Advances in VICTREX PEEK-based polymers are also expected, in order to keep up with the ever-increasing service temperature demands.

The increasing awareness and demand

and lower raw material costs year over year. As testing in harsh environments continues to show excellent performance

will continue to be an ideal metal and thermoset replacement for critical com-ponents in the oil and gas industry.Victrex Polymer SolutionsAutomated Dynamics

Figure 3: Themoplastics in composite tape can be bonded to metal for joining tubulars.

maintenance

Victrex Polymer Solutions300 Conshohocken State Road, Suite 120West Conshohocken, PA 19428PH: + (1) 800-VICTREXPH: + (1) 484-342-6001FX: + (1) 484-342-6002email: americas@victrex.comwww.victrex.com

Automated Dynamics407 Front StreetSchenectady, NY 12305 USAPH: +1 (518) 377-6471FX: +1(518) 377-5628email: sales@automateddynamics.comwww.automateddynamics.com