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A new type of high temperature retarder ZOC-H50S suitable for long cementing section (Part 1)

Abstract: With regard to slow development or super retarding happening at the top of cement slurry in deep and ultra-deep wells with long cementing intervals,a new type of cementing retarder ZOC-H50S was developed and its properties were evaluated. Thickening property tests different temperatures for slurry with cementing retarder ZOC-H50S and IR, DSC and TG analysis show that: cementing retarder ZOC-H50S has good temperature-resistance performance and stable molecular structure, It can be used at the bottom hole circulating temperature of 70 to 200℃. The thickening time of the slurry can be regulated effectively by adjusting the additive amount of cementing retarder ZOC-H50S.Thickening property tests for slurry with different salt contents show that cementing retarder ZOC-H50S has good sat-resistance performance and can be used in salty cement slurry.Strength development,thickening time,fluidity and API filtration of slurry with cementing retarder ZOC-H50S were studied at different top-bottom temperature differences.The results show that: The slurry with cementing retarder ZOC-H50S develops well in strength at large temperature difference and can overcome super retarding of the top of the slurry in long cementing interval. cementing retarder ZOC-H50S is applicable for large temperature range and can be used for slurry with both high and low densities. The slurry with cementing retarder ZOC-H50S has good overall performance,easy to regulate and control,and can satisfy cementing requirements for long cementing interval.

Key words:cementing retarder,cementing:long cementing interval;slurry,thickening time

The temperature difference between the top and bottom of the cement slurry column is very big in high geothermal gradient deep well cementing or deep well long cementing section cementing. The existence of large temperature difference (80 ~ 120 ℃) will lead to retarded or super retarded cement slurry column top, which not only delays the drilling process, but also increases the safety risk of subsequent drilling operation. Therefore, it is necessary to add high temperature cementing retarder ZOC-H50S in the cement slurry system to eliminate the problem of slow development of cement slurry strength at the top of long sealing section caused by large temperature difference. However, a new type of high temperature retarder has been synthesized due to its resistance to induction expansion. The high temperature cementing retarder ZOC-H50S is mainly composed of temperature resistant and salt resistant sulfonic acid groups, and double retarding groups are introduced. The double retarding group forms a solvation film on the surface of cement particles through adsorption, complexation, dispersion and wetting, and forms a very dense hydration layer on the surface of C-S-H and Ca (OH) Ψ, which inhibits the growth and development of crystal nucleus and reduces the hydration rate of cement particles. In addition, the group forms a micro soluble precipitation with Ca2 + through complexation, which reduces the concentration of Ca2 + in the liquid phase Now it is retarded. In addition, in order to form stable association mechanism between molecules and within molecules, Dy was introduced into the molecular structure.

The synthesized high-temperature cementing retarder ZOC-H50S molecules have the temperature sensing scalability, that is, the molecules are in the curling state at low temperature, and some retarding groups are "embedded" in the association mechanism; with the increase of temperature, the molecular chain gradually extends and the disassociation occurs, and the proportion of "exposed" retarding groups gradually increases, and the adsorption on the surface of cement particles changes from partial adsorption to full adsorption. Moreover, the process is reversible. Therefore, the cementing retarder ZOC-H50S has strong retarding effect at high temperature and partial adsorption at low temperature, which solves the contradiction between long thickening time at high temperature and slow development of low temperature strength.