Dispersive chlorine-free low-temperature early-strength agent used for oil well cement and cement mortar including same

Abstract

The invention provides a dispersive chlorine-free low-temperature early-strength agent used for oil well cement and a cement mortar including the same, belonging to the technical field of oil and gas well cementing. The low-temperature early-strength agent comprises, by weight, 1.5 to 2.5 parts of sodium sulfate, 0.6 to 1 part of nanometer silica, 0.15 to 0.3 part of sodium aluminate, 0.04 to 0.06 part of triethanolamine and 0.3 to 0.5 part of a water reducer. The low-temperature early-strength agent can effectively shorten time for waiting on cement setting during oil and gas well cementing at low temperature, substantially improves early strength of the oil well cement, enhances the rheological properties of the cement mortar and enables the oil well cement to have strength of 3.6 MPa in 12 h at 10 DEG C, strength of 8.2 MPa in 24 h at 10 DEG C, strength of 15.4 MPa in 12 h at 30 DEG C and strength of 28.8 MPa in 24 h at 30 DEG C; and the early-strength agent does not contain chloride ions and can be used together with lightening admixtures like hollow glass beads and floating beads so as to prepare cement mortar meeting different density requirements.

Description

technical field [0001] The invention relates to a dispersed chlorine-free low-temperature early-strength agent for oil well cement and cement slurry containing it, belonging to the technical field of oil and gas well cementing. The low-temperature early-strength agent prepared by the method is used for improving the early strength of cement stone in the cementing process of oil and gas wells. Background technique [0002] With the continuous development of oil and gas exploration and development to deep-water offshore oil and gas, coal bed methane, and shallow heavy oil, more and more low-temperature cementing (downhole circulation temperature below 45°C) operations are performed. CBM wells are relatively shallow, and the bottom hole temperature is generally between 25°C and 45°C, while the temperature of deepwater cementing is even as low as 4°C. Under low temperature conditions, the strength of oil well cement develops slowly, which prolongs the waiting time for setting a...

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Problems solved by technology

[0007] In view of the defects existing in the above-mentioned prior art, the object of the present invention is to provide a low-temperature early-strength agent for dispersed chlorine-free oil well cement and the cement slurry comprising it, which solves the problem that the existing early-strength agent containing nanomaterials makes the cement slurry Extreme thickening, chlorine-containing salt early strength agent increases the yield value of cement slurry, increases the permeability of cement stone and reduces the ability to resist sulfate corrosion, and the technical problem that dispersant needs to be added when mixing slurry

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