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The present invention provides cementing compositions for oil wells or the like comprising an hydraulic binder and reinforcing particles constituted by a flexible material of low compressibility, and with an average grain size of less than 500 μm. The compositions of the invention are of particular

The present invention provides cementing compositions for oil wells or the like comprising an hydraulic binder and reinforcing particles constituted by a flexible material of low compressibility, and with an average grain size of less than 500 μm. The compositions of the invention are of particular advantage when cementing zones which are subjected to extreme dynamic stresses, such as perforation zones and the junctions of a multi-branch lateral well. They are also highly suitable for producing plugs.

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1. A cementing composition, comprising: (i) an hydraulic binder; and (ii) reinforcing particles having an average grain size not exceeding 500 μm, and being formed from a flexible material selected from the group consisting of polyamide, polypropylene, polyethylene, styrene butadiene and styrene

1. A cementing composition, comprising: (i) an hydraulic binder; and (ii) reinforcing particles having an average grain size not exceeding 500 μm, and being formed from a flexible material selected from the group consisting of polyamide, polypropylene, polyethylene, styrene butadiene and styrene divinylbenzene and having a Poisson ratio of more than 0.3; and (iii) water in sufficient quantity to form a pumpable slurry when mixed with the binder and reinforcing particles. 2. A cementing composition as claimed in claim 1, wherein the reinforcing particles have an average grain size in the range 100 μm to 400 μm. 3. A cementing composition as claimed in claim 1, wherein the reinforcing particles are formed from a material having a Young's modulus of less than 5000 MPa. 4. A cementing composition as claimed in claim 3, wherein the particles are formed from a material having a Young's modulus of less than 3000 MPa. 5. A cementing composition as claimed in claim 4, wherein the particles are formed from a material having a Young's modulus of less than 2000 MPa. 6. A cementing composition as claimed in claim 1, wherein the density of the reinforcing particles is less than 1.5 g/cm3. 7. A cementing composition as claimed in claim 6, wherein the density of the reinforcing particles is less than 1.2 g/cm3. 8. A cementing composition as claimed in claim 1, wherein the material forming the reinforcing particles is selected from the group consisting of polyamide, polypropylene, polyethylene, styrene butadiene and styrene divinylbenzene. 9. A cementing composition as claimed in claim 1, further comprising at least one additive selected from the group consisting of suspension agents, dispersing agents, anti-foaming agents, retarders, setting accelerators, fluid loss control agents, gas migration control agents, and expansion agents. 10. A cementing composition as claimed in claim 1, wherein the reinforcing particles comprise 5% to 40% of the total volume of the slurry. 11. A cementing composition as claimed in claim 1, wherein the hydraulic binder comprises a cement. 12. A well cementing composition, comprising: (i) a cement; (ii) reinforcing particles having an average grain size in the range 80 μm to 500 μm, and being formed from a flexible material having a Poisson ratio of more than 0.3, the flexible material being selected from the group consisting of polyamide, polypropylene, polyethylene, styrene butadiene and styrene divinylbenzene; and (iii) water in sufficient quantity to form a pumpable slurry when mixed with the binder and reinforcing particles. 13. A cementing composition as claimed in claim 12, further comprising at least one additive selected from the group consisting of suspension agents, dispersing agents, anti-foaming agents, retarders, setting accelerators, fluid loss control agents, gas migration control agents, and expansion agents. 14. A cementing composition as claimed in claim 12, wherein the reinforcing particles comprise 5% to 40% of the total volume of the slurry.