Method for preparing cement additive

Abstract

The invention discloses a preparation method of a cement additive, which comprises the following steps: a) adding 4-8% by weight of acrylamide, 2-4% by weight of a crosslinking agent, 1-3.5% by weight of an initiator, 1- 4% by weight of the reinforcing agent and the rest of the water are cross-linked and polymerized under normal pressure to form a gel; b) drying and pulverizing the above-mentioned gel to obtain a cement additive. The cement additive prepared by the method of the invention is applied to the cement system of oil field cementing, which can prevent gas channeling, improve the cementing quality, and the qualified rate of the cementing quality is increased from the original 45% to more than 94%.

Description

technical field [0001] The invention relates to a preparation method of a cement additive, in particular to a preparation method of a cement additive used for oil field cementing. Background technique [0002] In view of shallow depth of reservoir, high oil-gas ratio, a large amount of natural gas dissolved in underground crude oil, low viscosity and low density of crude oil, when the oil layer is opened, when the pressure drops below the saturation pressure, the crude oil in the formation will be seriously degassed. During the process, the released gas escapes into the cement stone matrix, or enters the gap between the cement and the casing or the cement and the well wall, causing interlayer interleaving or even entering the wellhead, which eventually leads to low cement cement bond strength or interlayer channeling , Seriously affecting the quality of cementing, even if remedial measures such as cement extrusion are adopted, it is difficult to be effective, and it will adv...

AI Technical Summary

Problems solved by technology

[0002] In view of shallow depth of reservoir, high oil-gas ratio, a large amount of natural gas dissolved in underground crude oil, low viscosity and low density of crude oil, when the oil layer is opened, when the pressure drops below the saturation pressure, the crude oil in the formation will be seriously degassed. During the process, the released gas escapes into the cement stone matrix, or enters the gap between the cement and the casing or the cement and the well wall, causing interlayer interleaving or even entering the wellhead, which eventually leads to low cement cement bond strength or interlayer channeling , which seriously affects the quality of cementing. Even if remedial measures such as cement squeezing are adopted, it is difficult to be effective, and it will have adverse effects on subsequent oilfield operations such as water injection, acid fracturing, and layered mining, and even cannot be carried out.

In addition, due to the large difference between the oil layers, the high-pressure layer and the low-pressure layer exist at the same time. If the density of the cement slurry is increased to prevent gas channeling, it will cause pollution to the low-pressure layer, or even pressure leakage. Gas channeling affects the quality of cementing. In severe cases, formation oil, gas and water may channel to the surface