High performance rock bit grease

Abstract

The present disclosure relates to greases containing metal sulfonate thickeners. In one example the thickener may be a calcium sulfonate thickener. In other examples grease may contain a combination of a metal sulfonate thickener and another thickener, such as a metal complex soap grease, detergent, or non-soap thickener. The grease may be formulated to meet specific performance criteria relevant to lubrication of a roller cone drill bit in downhole conditions. The disclosure also relates to a roller cone drill bit containing a grease of the disclosure.

Description

PRIORITY CLAIM[0001]The present application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application Ser. No. 61 / 022,241, filed Jan. 18, 2008, incorporated by reference herein.TECHNICAL FIELD OF THE DISCLOSURE[0002]The present disclosure relates to a high performance grease compositions that provide good results in a journal bearing test or an oscillating stress level test. In an example embodiment, such a grease may include a primary calcium sulfonate thickener, and optionally, secondary thickeners, such as metal complex soap or non-soap grease thickeners, in combination with base oils and solid and oil soluble additive systems for lubricating journal bearing in a rock bit for subterranean drilling, such as a roller cone drill bit.BACKGROUND OF THE DISCLOSURE[0003]A wide variety of roller cone or rotary cone drill bits, which are a type of rock bit have been and are currently being used to form wellbores or boreholes in subterranean formations for oil, gas, ge...

AI Technical Summary

Benefits of technology

[0019]It is, therefore, the objective of embodiments of the present disclosure to provide novel grease compositions that are superior not only in the areas of improved load carrying and wear protection for rock bit applications with ever-increasing severity, but also in enhanced thermal stability and rheological / structural characteristics that make the grease more suitable as an effective and reliable pressure sensing media upon extended usage. These improvements discussed above may be measured using a journal bearing test and / or an oscillating stress level test. In further embodiments the grease compositions may also exhibit additional improvements such as a reduced tendency to impair seal performance or degrade surface coatings. In still further embodiments, the grease may be non-toxic.

Problems solved by technology

Such a roller cone drill bit, during the downhole drilling, is subjected to severe operating conditions such as constant and repetitive shock loads exerted to the interior portions of bearing surfaces with pressure in excessive of 15 MPa and temperature above 150° C.

For instance, calcium (lime) soap greases are highly resistant to water, but unstable at high temperatures.

Failures of the grease to deliver all of the functions mentioned above, namely, abilities to lubricate and reduce wear, seal and surface material compatibility, anti-corrosiveness, and adequate rheological responses, will result in the premature failures of the roller cone assembly and ultimately failures of the entire drilling operations which can not only cost dearly and significantly more than the cost of replacing defective parts but also consume precious time and energies to retrieve the failed bits and to resume drilling operations.

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