The Development Of The High Temperature Oil Well Cement Retarder

The theoretical basis and feasibility of this thesis come from the basic theory and the relevant research results of Portland cement hydration class G, come from the research results and the research and development train of thought for the oil well cement retarder. This article identified the copolymer as the designed objective product, through designing the molecular structure of copolymer retarder, selecting the polymer monomer and polymerization initiator, designing the synthesis process of polymerization reaction and characterizing the polymer by IR, H-NMR and TG-DSC.This thesis confirmed the law of the retarder influence on the performance of the cement by the experiments of the compressive strength and the thicking experiments; exploring researched the internal cause, which for the retarder effect on the cement performance, and the retardation mechanism of the copolymer by XRD and SEM. The results of this thesis have a certain reference value and significance for the research and development of high temperature retarder for oil cement.The specific research works in this thesis are as follows:(1) This thesis designed copolymer retarders of two systems, which are2-acrylamide base-2methyl c sulfonic acid (AMPS)/styrene sulfonic acid sodium (SSS)/itaconic acid (IA) and2-acrylamide base-2methyl c sulfonic acid (AMPS)/styrene sulfonic acid sodium (SSS)/maleic anhydride (MAH); and respectively confirmed the best formulas of the copolymer retarders, in the conditions of acid and alkaline by orthogonal experiments. The best formula of AMPS/SSS/IA in alkaline condition:the optimum reaction condition was pH=7in the solution,3%concentration by mass of the initiator in total monomers, the reaction time was5hours, reaction temperature was60℃, the molar ratio of the monomer AMPS,IA,SSS was3:2:1. The best formula of AMPS/SSS/IA in acid condition:4%concentration by mass of the initiator in total monomers, the optimum reaction condition was pH=1in the solution, the molar ratio of the monomer AMPS,IA,SSS was3:2:2, reaction temperature was80℃, the reaction time was5h. The best formula of AMPS/SSS/MAH in alkaline condition:the optimum reaction condition was pH=11in the solution,4%concentration by mass of the initiator in total monomers, the reaction time was6h, the reaction temperature was60℃, the molar ratio of the monomer AMPS,MAH,SSS was3:2:2. The best formula of AMPS/SSS/MAH in acid condition:the reaction temperature was70℃,3%concentration by mass of the initiator in total monomers, the reaction time was6h, the optimum reaction condition was pH=5in the solution, the molar ratio of the monomer AMPS,MAH,SSS was3:2:1.(2) The results, which of the performance comparation of the retarders in the acid and alkaline conditions, showed that the retarders in the alkaline conditions had more excellent comprehensive performances. The results, which of the performance comparation of the retarders of AMPS/SSS/IA and AMPS/SSS/MAH in the alkaline condition by the experiments of compressive strength and thicking experiments, showed that both of the two kinds retarders had less effection on the cement strength, the retarder addition amount and the atmospheric pressure thicking time were in a linear relationship and had good high thicking performance. The results of theperformance comparaton of the two kinds of systems retarders in the alkaline condition show that the comprehensive performance of AMPS/SSS/IA are better than AMPS/SSS/MAH.(3) The results by the analysis test of XRD and SEM showed that, although the molecular structures of the two systems retarders are similar, but their performance had some differences and had different effection on the cement struction. In the same condition, the retarder AMPS/SSS/IA in alkaline condition mainly caused C-S-H and ettringite crystal formation; the retarder AMPS/SSS/MAH in alkaline condition mainly caused the formation of ettringite, but the calcium silicate gel nearly without change.(4) This thesis exploring researched the tetardation mechanisms of AMPS/SSS/IA and AMPS/SSS/MAH by XRD and SEM. The tetardation mechanism of AMPS/SSS/IA in alkaline condition:the copolymer AMPS/SSS/IA prevented Ca (OH)2crystal formation and growth mainly through reacting with the free Ca2+and producing complex chelates, which were adsorption on the Ca(OH)2crystal nucleus surface; besides, the copolymer AMPS/SSS/IA reduced the cement hydration rate because that the copolymer promoted the early hydration of C3S in a certain degree and caused C-S-H thicking, which increased the transportaion resistance of the particles. The tetardation mechanism of AMPS/SSS/MAH in alkaline condition:the copolymer AMPS/SSS/MAH prevented Ca (OH)2crystal formation and growth mainly through adsorpting on the "rich silicon layer", which were formed during the C3S hydration, reacting with the free Ca2+and producing complex chelates.