| With the decrease of domestic energy,oil and gas development is developing towards deep wells and ultra-deep wells.Complex geological conditions and high temperature and high pressure environmental conditions have brought great challenges to cementing engineering.Under high temperature and pressure,cement slurry is easy to be quickly thickened,which seriously shortens the pumping time and threatens the safety of cementing.In order to meet the requirements of cementing,it is necessary to add additives in cement slurry.At present,the retarders used in our country have some problems,such as poor high temperature resistance,poor salt resistance and core wrapping,which endanger the cementing safety.In this thesis,three retarders named GWH-1,HX-400 and DRH-200L were compared in terms of thickening property,salt resistance,compressive strength and compatibility and so on.The results showed that the three retarders had some problems,such as poor salt resistance,great influence of early strength and abnormal gelation.By means of scanning electron microscopy,X-ray diffraction and X-ray photoelectron spectroscopy,the abnormal gelatinous phenomena of cement slurry with less polycarboxylic acid additives at 120? were studied theoretically.It was found that the abnormal cementitious phenomena of cement slurry were due to the weakening of complexation and adsorption of polycarboxylic acid additives at high temperature,which could not hinder the hydration process.Under the action of shear rate,the cement slurry was wrapped around the axle,and the macroscopic performance was abnormal cementing of cement slurry.In view of the existing problems,a quinary polymer was designed according to the molecular structure.The polymer was composed of 2-acrylamide-2-methylpropionic sulfonic acid(AMPS),N-vinylpyrrolidone(NVP),sodium styrene sulfonate(SSS),itaconic acid(IA)and acrylic acid(AA)as monomers.The retarder was named PAINAS.The molecular structure of the polymers was evaluated by IR and NMR.The results showed that all monomers participated in the reaction.The thermogravimetric analysis and liquid chromatography gel permeation chromatograph were used to test the heat resistance and molecular weight of the polymers.The results showed that the temperature resistance of the polymer reaches 350? and the molecular weight of the polymer is 50000.The thickening property of cement slurry mixed with PAINAS was evaluated in this thesis.The results showed that the retarder could be used at 160? and was insensitive to temperature and dosage in the range of 130-160?.Through salt resistance and stability evaluation,it was found that the retarder could tolerate 15%salt water and had good sedimentation stability.The difference between upper and lower density was only 0.02g·cm-3.The evaluation of water loss and strength of cement slurry showed that the retarder had good compatibility with water loss reducer,and the early compressive strength of cement stone with PAINAS developed well without abnormal cementing phenomenon,and its comprehensive performance was excellent in the field application of cement slurry system. |
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