Fiber Reinforced Elastomeric Stator

Abstract

Embodiments disclosed herein relate to a composition useful for forming stator or a portion thereof. The composition may include: a curable elastomer; a fiber fibrous compound; a fiber dispersion compound; and optionally carbon black.

Description

FIELD OF THE DISCLOSURE[0001]Embodiments disclosed herein relate generally to stators used with positive displacement drilling motors. More specifically, embodiments disclosed herein relate to a fiber reinforced stator, and compositions for forming the fiber reinforced stator, wherein the fiber is easily incorporated and well dispersed throughout the elastomeric matrix.BACKGROUND[0002]Moineau style hydraulic motors and pumps are conventional in subterranean drilling and artificial lift applications, such as for oil and / or gas exploration. Such motors make use of hydraulic power from drilling fluid to provide torque and rotary power, for example, to a drill bit assembly. While downhole drilling motors fall into the general category of Moineau-type motors, they are generally subject to greater working loads, temperatures, and more severe chemical and abrasive environments than Moineau motors and pumps used for other applications. As such, the demands on drilling motor components (roto...

AI Technical Summary

Benefits of technology

[0009]A novel method has now been developed to disperse aramid fibers or other fibers into an elastomeric matrix via injection molding or extrusion molding, overcoming one or more of the above noted deficiencies. It has been found that improved processability and dispersion of fibers throughout an elastomeric matrix may be achieved by admixing fibers and a fiber dispersion compound, such as amorphous silicon dioxide, with an elastomeric material. It is theorized, for example, that the highly spherical geometry of the amorphous silicon dioxide provides a physical bearing effect, and as a result, the processability of the admixture and incorporation of a limited amount of the fiber and interaction of the fiber with the elastomeric matrix are greatly improved.

Problems solved by technology

While downhole drilling motors fall into the general category of Moineau-type motors, they are generally subject to greater working loads, temperatures, and more severe chemical and abrasive environments than Moineau motors and pumps used for other applications.

As such, the demands on drilling motor components (rotor and stator components) typically far exceed the demands on the components of other Moineau-type motors and pumps.

Achieving suitable processability (e.g., flowability) in order to injection mold the elastomer materials tends to be difficult at such lengths.

Moreover, many rubber compounds are known to deteriorate in the presence of hydrocarbons.

One drawback with conventional stators including an all elastomer helical cavity component is that a tradeoff in elastomer properties has been required.

This is particularly true in injection-mold processes . . . . Typically, a stiffer compound will demand much more processing power and time, thereby increasing manufacturing costs” (column 4, lines 4-12).

Guo's teaching is consistent with conventional wisdom in the art, which suggests that rigid elastomers (e.g., those having a Shore A hardness of about 90 as well as other mechanical properties described in more detail below) are not suitable for use in downhole stators due to inherently poor processability.

One significant drawback with conventional stators is that the elastomer helical cavity component deforms under torque loads (due to the low rigidity of the elastomer).

Thus, flexibility of the liner may lead to incomplete sealing between the rotor and stator such that available torque may be lost when the rotor compresses the stator lobe material, thereby reducing the power output of the PDM.

Additional problems may be encountered with stators when, for example, rotation of the rotor within the stator shears off portions of the stator lobes.

This process, which may be referred to as “chunking,” deteriorates the seal formed between the rotor and stator and may cause failure of the PDM.

Chunking may be increased by swelling of the liner or thermal fatigue.

Swelling and thermal fatigue may be caused by elevated temperatures and exposure to certain drilling fluids and formation fluids, among other factors.

Fiber reinforcement, to date, has presented significant manufacturing difficulties as it is difficult to achieve desired stator properties using injection molding techniques, such as due to due to fiber settling or agglomeration, poor dispersion of the fiber throughout the elastomeric matrix, excessive viscosity of the elastomeric composition when incorporating the fibers (i.e., poor processability or a very limited processing window unsuitable for injection molding processes at the fiber loadings necessary to achieve the desired properties), among other shortcomings.

The poor dispersion of the fiber via such processes impairs the elastomeric compound static and dynamic properties as well as performance consistency.

As a result, fiber reinforcement via injection molding requires additional costly and labor-intensive manufacturing steps, such as weaving or placement of the fibers or a fibrous mat within or around a mold, and the manufacturing processes generally produce either a different concentration of fibers per unit volume of elastomer between the thick portions of the lobes and the thin portions (which reduces the mechanical strength of the liner) or, when fibers are disposed manually, a different number of layers must be applied in the thick portions of the lobes as compared to the thin portions.

Due to the aforementioned reasons, fiber reinforced elastomeric stators have not been commercially successful.

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