Thermoset particles with enhanced crosslinking, processing for their production, and their use in oil and natural gas driliing applications

Abstract

Thermoset polymer particles are used in many applications requiring lightweight particles possessing high stiffness, strength, temperature resistance, and/or resistance to aggressive environments. The present invention relates to the use of methods to enhance the stiffness, strength, maximum possible use temperature, and environmental resistance of such particles. One method of particular interest is the application of post-polymerization process step(s) (and especially heat treatment) to advance the curing reaction and to thus obtain a more densely crosslinked polymer network. The most common benefits of said heat treatment are the enhancement of the maximum possible use temperature and the environmental resistance. The present invention also relates to the development of thermoset polymer particles. It also relates to the further improvement of the key properties (in particular, heat resistance and environmental resistance) of said particles via post-polymerization heat treatment. Furthermore, it also relates to processes for the manufacture of said particles. Finally, it also relates to the use of said particles in the construction, drilling, completion and/or fracture stimulation of oil and natural gas wells; for example, as a proppant partial monolayer, a proppant pack, an integral component of a gravel pack completion, a ball bearing, a solid lubricant, a drilling mud constituent, and/or a cement additive.

Description

[0001] This application claims the benefit of U.S. Provisional Application No. 60 / 689,899 filed Jun. 13, 2005.FIELD OF THE INVENTION [0002] The present invention relates to lightweight thermoset polymer particles, to processes for the manufacture of such particles, and to applications of such particles. It is possible to use a wide range of thermoset polymers as the main constituents of the particles of the invention, and to produce said particles by means of a wide range of fabrication techniques. Without reducing the generality of the invention, in its currently preferred embodiments, the thermoset polymer consists of a terpolymer of styrene, ethyvinylbenzene and divinylbenzene; suspension polymerization is performed to prepare the particles, and post-polymerization heat treatment is performed with the particles placed in an unreactive gaseous environment with nitrogen as the preferred unreactive gas to further advance the curing of the thermoset polymer. When executed in the mann...

AI Technical Summary

Benefits of technology

[0027] As was discussed earlier, Nishimori, et. al. (JP1992-22230) used heat treatment to increase the compressive elastic modulus of their S-DVB particles (intended for use in liquid crystal display panels) significantly at room temperature (and hence far below Tg). Deformability under a compressive load is inversely proportional to the compressive elastic modulus. It is, therefore, important to consider whether one may also anticipate major benefits from heat treatment in terms of the reduction of the deformability of thermoset polymer particles intended for oil and natural gas drilling applications, when these particles are used in subterranean environments where the temperature is far below the Tg of the particles. As explained below, the enhancement of curing via post-polymerization heat treatment is generally expected to have a smaller effect on the compressive elastic modulus (and hence on the proppant performance) of thermoset polymer particles when used in oil and natural gas drilling applications at temperatures far below their Tg.

[0028] Nishimori, et. al. (JP1992-22230) used very large amounts of DVB (wDVB>>0.2). By contrast, in general, much smaller amounts of

Problems solved by technology

As discussed above, particles made from polymeric materials have historically been considered to be unsuitable for use by themselves as proppants.

However, these inventors still did not consider or describe the polymeric particles as proppants.

However, embodiments of this prior art, based on the use of styrene-divinylbenzene (S-DVB) copolymer beads manufactured by using conventional fabrication technology and purchased from a commercial supplier, failed to provide an acceptable balance of performance and price.

The need to use a very large amount of an expensive crosslinker (50 to 80% by weight of DVB) in order to obtain reasonable performance (not too inferior to that of Jordan Sand) was a key factor in the higher cost that accompanied the lower performance.

While not improving the extent of covalent crosslinking relative to conventional isothermal polymerization, rapid rate polymerization results in the “trapping” of an unusually large number of physical entanglements in the polymer.

There is no prior art that relates to the development of heat-treated thermoset polymer particles that have not been reinfor

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