A thread compound, containing graphite, grease and usual additives, a process for the preparation thereof and the use of said compound

Description

[0001] The invention relates to a thread compound, containing graphite, grease and usual additives, to a process for the preparation thereof and to the use of said compound.

[0002] Lubricants containing graphite, mica or talc as solid material are described in the U.S. patent Nr.2,581,407.

[0003] Furthermore, the U.S. patent 3,007,866 discloses drill pipe lubricants containing graphite as an active lubricating ingredient.

[0004] In general, a suitable thread compound should have important properties, such as lubrication of male and female threads to prevent galling when screwed together, maintain separation of male and female threads under conditions of extreme pressure, especially when screwed together, prevent or resist corrosive attack on threads under various conditions, including maritime transport, and ensure complete seal of screw components to prevent leakage through threaded areas.

[0005] In the petroleum industry a considerable variety of thread compounds is used for many years which have fulfilled the above-mentioned requirements. These prior art thread compounds contain metals, metal powders and earthen powders as well as greases.

[0006] It is known that the petroleum industry is an extensive user of screwed tubular products and components in such applications as drill strings, production strings, casing and line pipe. Therefore, the American Petroleum Institute (API) issued a Bulletin, Nr. 5A2, April 1972, on thread compounds, casing tubing and line pipe.

[0007] The said compound, recommended by said API-Bulletin 5A2 contains as high as 30.5%, by weight, of lead in the form of finely divided powder, which performs as an extreme pressure ingredient. Furthermore, this recommended thread compound contains 12.2%, by weight, of zinc and 3.3%, by weight, of copper. In particular, lead and its compounds may have serious disadvantages, especially direct health hazards for the user of said thread compound. Furthermore, lead and lead compounds are undesired because of environmental pollution of surface waters and land areas.

[0008] Another disadvantage of API Modified Thread Compound is that it has been demonstrated to be substantially ineffective as a protectant to prevent corrosion of threads during storage or marine transportation. This is especially important to manufacturers of premium connections who transport their products to many parts of the world, in addition to which they may be stored off-shore. It is thought that the corrosion problem with-API Modified Thread Compound is intrinsic to the presence of copper, and more electro-positive metals. The copper is present to 3%, by weight, as an anti-galling agent. In addition, the type of greases required by the API Bulletin 5A2, normally contains soap gellants, which may leach out under water, glycols and relatively low molecular weight oils which will vaporize in outdoor conditions, even at low temperature conditions, so that a joint doped with API Modified Thread Compound will be dry and flaky more often than not after about 6 months and will show exposed areas of metal on the threads.

[0009] The invention aims now to provide an improved thread compound without the above-mentioned disadvantages of the prior art thread compounds but still having the important properties required by said compounds.

[0010] Accordingly, the invention relates to a thread compound containing graphite, grease and usual additives, characterized in that said thread compound comprises 20-50%, by weight, of powdered graphite, 10-25%, by weight, of powdered talc, and balance to 100%, by weight, of grease and the usual additives.

[0011] The thread compounds according to the invention do not contain lead or lead compounds, but still have the above-mentioned desired properties.

[0012] As mentioned before, the new compounds of the invention contain no lead or lead compounds. It is now surprising that the present thread compounds without lead do possess the desired properties. The new compounds of the invention may successfully be applied to threaded areas of male and female components to be screwed by means of brushes, sprays, spatulas and the like, whereby the threads may be screwed without galling under loaded or unloaded conditions.

[0013] The main advantages of the present thread compound may be summarized as follows: long term protection against general and pitting corrosion of threads; excellent lubricity enabling single and multiple make-ups and break- aways of assemblies for testing and storage; more than sufficient sealing properties; absence of lead in the formulation, thereby eliminating health and environmental hazards associated with this metal (API Modified Thread Compound contains 30.5%, by weight, of lead); smooth compounds of water resistant greases that will readily wet and adhere to threads at all temperatures; and economical in price by comparison with the prior art thread compounds.

[0014] Furthermore, it appeared that by use of the present compound the screwed threaded compounds are leach free under reasonable performance conditions. The present thread compounds are able to adequately fill and be retained in the spaces between the threads during service to prevent leakage after being screwed. Thread compounds according to this invention have been extensively tested under normal working conditions showing no tendency to permit leakage. During hydrolic testing "make-up" and "break out" indicates more than enough lubricity by preferred thread compound compositions to enable tightly screwed threads to be broken without galling.

[0015] Preferred thread compounds of the invention comprise 28-35%, by weight, of the powdered graphite, 14-17.5% by weight, of the powdered talc, and balance to 100%, by weight, of the grease and the usual additives.

[0016] Surprisingly good results may be obtained when in the thread compound the amount of talc is about 50%, by weight, of the amount of the graphite.

[0017] Furthermore, the invention relates to a process for the preparation of the thread compound, wherein the powdered graphite, the powdered talc and the usual additives in the appropriate amounts are mixed thoroughly and the obtained mixture is uniformly dispersed in the appropriate amount of said grease, as well as to the use of the present thread compounds for threads of casing, line pipe and other tubulars in the petroleum industry as well as in drilling operations.

[0018] However, the working mechanism of the present compound is not understood. It is thought that the manner in which each of the compounds ball or roll up and cleave under pressure, is important and that the mixture of the two main compounds, i.e. powdered graphite and powdered talc, provides a synergistic effect. In any case, testing results demonstrate that higher loads may be accommodated with lower torque than with the prior art API Thread Compound. It appeared furthermore that the present compound has an improved lubricity over said API Modified Thread Compound. This matter is of considerable importance in the petroleum industry, where the particular property, known as "slick", is required of thread compounds used on casing and line pipe, whereby threads can be tightened without the use of excessive torque. Considerable benefits in drilling practices should arise.

[0019] The invention will be illustrated by means of the following example.

EXAMPLE

[0020] A thread compound of the invention is prepared by thoroughly mixing of 32 parts of powdered graphite and 16.0 parts of powdered talc. The obtained homogeneous dry mixture is added to 52 parts of a mixture of grease and other compounds and then uniformly dispersed obtaining the desired thread compound.

Claims

- 1. A thread compound, containing graphite, grease and usual additives, characterized in that said thread compound comprises 20-50%, by weight, of powdered graphite, 10-25%, by weight, of powdered talc, and balance to 100%, by weight, of grease and the usual additives.

2. The thread compound according to claim 1, characterized in that said compound comprises 28-35%, by weight, of the powdered graphite, 14-17.5%, by weight, of the powdered talc, and balance to 100%, by weight, of the grease and the usual additives.

3. The thread compound according to claim 1 or 2, characterized in that in said compound the amount of talc should be about 50%, by weight, of the amount of the graphite.

4. The thread compound according to claims 1-3, characterized in that said grease is a relatively high molecular weight hydrocarbon.

5. The thread compound according to claims 1-4, characterized in that said additive is a corrosion inhibitor.

6. A process for the preparation of the thread compound of the claims 1-5, characterized in that powdered graphite, powdered talc and usual additives in the appropriate amounts are mixed thoroughly and the obtained mixture is uniformly dispersed in the appropriate amount of said grease.

7. The use of the said compound of claims 1-5 for threads of casing, line pipe and other tubulars in the petroleum industry as well as in drilling operations.