High-density mud conversion to cement slurry cementing fluid

Abstract

The invention discloses a high-density MTC cementing fluid with density between 2.2-2.7g / cm3, of which components and mass ratio are: slag micro-powder of 100 quotient, weighting material of 50-600 quotient, stabilizer of 3-10 quotient, suspending agent of 0.5-5 quotient, drilling fluid of 15-55 quotient, water of 35-130 quotient, dispersant of 3-15 quotient, retarder or coagulator of 0.5-3 quotient, and pH value regulating agent of 1.5-15 quotient. Specific surface area of the slag micro-powder is between 200-800m2 / kg, and iron ore powder of 200 or 325 mesh or mixture of the same are used as the weighting material. The cementing fluid is consistent with drilling fluid, adhesive matter does not formed after mixing, thereby displacement efficiency is increased; capability of resistance to drilling fluid pollution is strong; filtration-reducing material in high-density drilling fluid can be used to control stability of system and reduce cost of system. Advantages of the cementing fluid are: good strength development at high temperature, not brittle fracture at high temperature, and good long-period sealing property.

Description

Technical field [0001] The invention relates to cementing fluids for oil and gas wells, in particular to MTC cementing fluids of high-density cementing technology. Background technique [0002] Cementing of high-pressure oil and gas wells requires the use of high-density cementing fluids. High-density cement slurry is used to cement high-pressure oil and gas wells. When high-density cement slurry is used to replace high-density drilling fluid, the cement slurry and drilling fluid are difficult to be compatible with the drilling fluid, and the displacement efficiency cannot be fully guaranteed. This seriously affects the cementing quality of high-pressure oil and gas wells. , Causing a series of difficulties for the follow-up operations of high-pressure oil and gas wells. In addition, in order to ensure the comprehensive engineering performance of high-density cement slurry, imported treatment agents are used to prepare the slurry, which makes the cost of the system high. For exam...

AI Technical Summary

Problems solved by technology

[0005] To prepare ultra-high-density MTC, a large amount of weighting material must be added to the system, and at the same time, the amount of slurry mixing water should be reduced as much as possible. However, whether adding weight material or reducing the amount of slurry mixing water will make the system Severe thickening reduces the fluidity of the system, or even does not make a slurry at all

In addition, high-density MTC has a thick slurry at room temperature, making it difficult to disperse effectively. However, under high-temperature conditions in the well, the slurry will become thinner to a certain extent, and there is a large gap between the high-density material and MTC. Therefore, during the waiting solidification process, the weighted material is easy to sink in the MTC, and the system will become unstable due to the settlement of the system, which will make the system components uneven, and then affect the comprehensive engineering performance of the system. The light performance cannot meet the design requirements, and the heavy cause cementing quality accidents

In addition, the weighting material itself does not have any cementing effect, so adding a large amount of it will inevitably reduce the percentage of cementing components in the system, and then significantly reduce the compressive strength of the system, making it difficult for the compressive strength to meet the requirements of interlayer isolation

Furthermore, compared with conventional density cement slurry and MTC, it is more difficult to match the comprehensive engineering performance of ultra-high density MTC

The higher the density of MTC, the more serious the above problems. Therefore, it is still difficult to see the density up to 2.2g / cm 3 The ultra-high MTC reported above

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