Cement paste for cementing low-temperature well and preparation method of cement paste

Abstract

The invention relates to cement paste for cementing a low-temperature well and a preparation method of the cement paste. The preparation method sequentially comprises the following steps: (1) pouring 4.8-12 parts of a fluid loss agent and 2.4 parts of a dispersing agent USZ into 352 parts of deionized water, and uniformly stirring; (2) carrying out dry powder mixing on 800 parts of G-grade oil well cement, 16-24 parts of calcium chloride and 32-40 parts of silica fume; and (3) putting the mixed dry powder into the solution in the step (1), and uniformly stirring to obtain the cement paste for cementing the low-temperature well. The preparation method of the fluid loss agent sequentially comprises the following steps: dissolving 6-8 parts of polyvinyl alcohol PVA1788 in 100 parts of deionized water to prepare a polyvinyl alcohol aqueous solution; adding 10-13 parts of a cross-linking agent glutaraldehyde, stirring and heating to 50-60 DEG C; adjusting the pH value to 4-5 by using concentrated hydrochloric acid, continuously stirring for 1 hour, and carrying out chemical reaction under an acidic condition; and adjusting the pH value to 7-8 by using a NaOH solution, cooling to room temperature, adding 1-1.5 parts of a formaldehyde solution, and uniformly mixing to obtain the fluid loss agent. The cement paste can adapt to a low-temperature well environment below 60 DEG C, and is short in cement waiting time, rapid in strength development and high in construction safety.

Description

technical field [0001] The invention relates to oil and gas cementing, in particular to a cement slurry for low-temperature well cementing; the invention also relates to a preparation method of cement slurry for low-temperature well cementing, which belongs to the technical field of low-temperature well cementing. Background technique [0002] At present, the oil well cement used in well cementing is Portland oil well cement. The outstanding problems are that the cement slurry has a long setting time and slow strength development, especially in low temperature shallow wells below 60 ° C. Due to shallow wells and low ground temperature, The strength of oil well cement develops slowly, and the waiting time is long, which increases the drilling cost, and easily causes annular channeling, which affects the cementing quality and operation safety. It is difficult for cement slurry to form a high enough strength within the normal required waiting time, which cannot meet the needs o...

AI Technical Summary

Problems solved by technology

[0004] At present, the common defects of fluid loss reducers in commonly used cement slurries are: 1. Various cellulose ethers are commonly used in oil well cement fluid loss reducers, including carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), carboxymethyl hydroxyethyl cellulose (CMHEC), etc.

[0005] 2. At present, the water loss reducing agents on the market focus on solving the performance of cement slurry under high temperature conditions, and lack the performance evaluation of cement slurry under low temperature conditions

In most cases, delays of more than a week lead to rejection, resulting in waste and increased production costs

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