Expansion agent for oil well cement and preparation method thereof

Abstract

The invention discloses an expanding agent for oil well cement and a preparation method of the expanding agent, relates to an oil well cement additive for well cementation, belongs to the technical field of oilfield chemistry, and aims to provide an expanding agent with a wide use range and a good set cement expansion rate for oil well cement and a preparation method of the expanding agent. The expanding agent for the oil well cement consists of the following substances in percentage by mass: 12-18% of CaO, 12-18% of CaCl2, 28-35% of MgO, 28-35% of MgSO4 and the balance of slag with activity, wherein the slag is an aluminosilicate material; the activity of slag refers to hydraulic activity of slag. The expansion rate of the expanding agent to set cement can be up to 0.5-1.7%, and the expanding agent has an expansion effect on set cement at 50-205 DEG C, is free of adverse effect on other properties of cement slurry, can be used in fresh water, saline water, seawater and high mineralized water, and is wide in raw material resource, low in cost and simple in manufacturing process.

Description

technical field [0001] The invention relates to an oil well cement additive for well cementing, belonging to the technical field of oil field chemistry. Background technique [0002] After the oil well cement slurry is hydrated and solidified and hardened, the volume of the cement stone will shrink because the specific gravity of the reactant is lower than that of the reaction product, that is, "chemical shrinkage". The volume shrinkage rate of the cement stone is generally 1 to 2%. During the process, due to the volume shrinkage phenomenon, the cement slurry originally filled between the formation and the casing often has small gaps or micro-rings on the two interfaces between the cement and the formation and between the casing and the formation. This shrinkage directly affects the quality of cementing, provides a possible channel for oil and gas water channeling, and seriously affects later oil production, water injection and other engineering operations. [0003] Therefo...

AI Technical Summary

Problems solved by technology

[0004] At present, the commonly used oil well cement expansion agents have certain limitations: ① At present, most water and oil well cement expansion agents mainly react with cement to form ettringite crystals, but when the temperature exceeds 70°C, ettringite crystals are unstable and turn into denser calcium thioaluminate hydrate and gypsum, which cannot expand; ②The finely ground aluminum powder expansion agent mainly produces tiny hydrogen bubbles to produce expansion, but it can only be used in shallow wells In applications, because in deep wells, the formation pressure will exceed the expansion pressure of the bubbles

The clinker raw material formula is: bauxite (Al 2 o 3 ) (50%~65%), limestone (CaO) (30%~40%), gypsum (CaSO 4 ) (5%~15%), coal ash (<10%), heat the ingredients to 1320°C~1380°C, take 35%~40% and 60%~65% anhydrite to grind together to form an expansion agent, the expansion agent When the temperature is higher than 150°C, the expansion effect is not ideal, and the fluidity is low, which affects the overall performance of the cement slurry

[0007] Publication No. CN1034218A patent document "An Anti-clay Expansion Agent for Oil Exploitation and Preparation Method", is a kind of anti-clay expansion agent for oil drilling and mining, which is composed of polyethylene polyamine hydrochloride hydrochloride Polyacrylamide-based polymer chemical treatment agent as the main component, it is used in drilling mud, oil field fracturing, acidification process with the characteristics of a multi-purpose agent, strong anti-scouring ability, excellent performance, simple process and low cost, etc. This agent is an additive to prevent expansion and cannot be used to promote cement stone expansion

[0008] Publication No. CN1139079A patent document "ferroaluminate expansion agent" is a kind of ferroaluminate expansion agent, using limestone, fly ash, iron powder, etc. as raw materials, after grinding, calcining, adding appropriate amount of gypsum, Made by grinding, it can be used to improve the impermeability of cement concrete or to produce expansive self-stressed cement. This expansive agent is mainly used in construction cement, and it is difficult to adjust rheological properties, so it is not suitable for use in oil well cement.

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