Lightening admixture

Abstract

The invention discloses a lightening admixture. The lightening admixture is characterized in that a main ingredient is a high-molecular polymer; the density of cement paste can be reduced to 1.78-1.15 g / cm<3> or less when the mixing quantity is 1-200% of the amount of cement. Compared with the prior art, the lightening admixture has the advantages that the lightening admixture is available in materials, strong in machinability, fine in obtained powder, low in density, non-absorbent, corrosion-resistant, high in withstand pressure of solid particles, free of crushing, wide in adaptive temperature range, stable in chemical properties, and free of poison and taste, can be directly blended into dry cement powder in a dry manner, and can also be compounded with additives such as a retarder, a fluid loss agent, a dispersing agent, a deformer and the like, and other lightening admixtures; low-density cement paste with excellent rheological property can be prepared in absence of additionally added construction equipment; lightweight set cement with strong compactness, good elasto-plastic property and high strength can be formed; the lightening admixture is especially suitable for implementing balance pressure on leaky stratum, so that well cementation is carried out; well leakage is prevented; the quality is ensured; the service life of oil and gas wells is prolonged.

Description

technical field [0001] The invention relates to a lightening agent, in particular to an oil well cement lightening agent in the technical field of drilling and cementing. Background technique [0002] Low-pressure leaky formations are prone to lost circulation not only during drilling, but also during cementing. Lost circulation will cause the cementing slurry to fail to return to the designed position, and the effective sealing and isolation of the formation cannot be guaranteed. Poor cementing quality is very harmful. [0003] The basic cement density under national standards and API standards is 3.15g / cm 3 The optimal density of the prepared cement slurry is 1.88~1.90g / cm 3 , with the help of related additives, it can generally be at 1.78-1.98g / cm 3 about. When the equivalent density is lower than 1.78g / cm 3 When cementing wells in leaky formations, it is common practice to add some lightweight materials called lightening agents to the cement. The density of this l...

AI Technical Summary

Problems solved by technology

[0004] The lightening agents used in the past mainly include bentonite, fly ash, slag, etc., which have played a role in reducing the density of cement slurry to a certain extent, but the low-density cement slurry system prepared with these lightening agents has complex preparation processes and poor stability. , low cement strength, high permeability, easy to crack and other defects, can not fully meet the requirements of cementing operations in deep wells prone to leakage

[0005] Chinese patent ZL201010135449.0 discloses "non-floating bead low-density cement". The lightening agent used is a combination of nano wollastonite and fly ash, and the density that can be reduced is difficult to meet less than 1.60g / cm 3 grout requirements

Chinese patent ZL200910310954.1 discloses "high-temperature low-density cement slurry and its application". In deep well cementing, but its density can only be controlled at 1.30~1.60g / cm 3 between, difficult to lower

Chinese patent ZL200410092887.8 discloses "thixotropic early-strength anti-channeling low-density cement slurry" using floating beads as a lightening agent, and the minimum density of cement slurry can be reduced to 1.25g / cm 3 , but because the floating beads themselves have hollow walls and are brittle and easy to break, they can only be mixed at a low shear rate of 4000rpm. When the slurry is mixed at a standard speed of 12000rpm, the performance of the cement slurry will change greatly, and the performance cannot be reached. to design requirements

However, it is expensive and difficult to use widely

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