Preparation Of Zwitterionic Retarders For Large Temperature Difference And Its Application In Light Weight Cement Slurry

With the development and exploration of oil and gas field into the deep well and ultra deep well, the complexity of geological conditions has brought many difficulties and challenges for well cementing engineering, especially for the long cementing section with low pressure.The light weight cemeng slurry and retarders characterized by high temperature resistant and excellent adaptation to the large temperature difference are required. However, the conventional retarders has poor temperature resistance and poor ability to adapt to the large temperature difference.Therefore, based on the requirements of cementing retarders for large temperature differenc, this paper focused on the large temperature difference zwitterionic retarders and its application in the low density cement slurry system. Some research finding are as follows:(1) Large temperature difference zwitterionic retarder (PAID) was prepared by the copolymerization of 2-methyl-2-acrylamide-propyl sulfonic acid (AMPS),itaconic acid (IA), methyl acryloyl oxygen ethyl trimethyl ammonium chloride (DMC) and methyl allyl polyoxyethylene ether (HEPG). On the basis of single factor experiments, the synthetic reaction conditions were teste by using response surface methodology.And the optimum synthesis conditions are as follows:monomer mole ratio of AMPS, IA, DMC and HPEG is 50:25:10:0.02, the 1.2wt% of K2S2O8 dosage,31wt% of monomer concentration,5 h of the reaction time,66? of the polymerization temperature, and the pH is 8. The FTIR, NMR, TG, DSC, GPC, SEM and other testing methods were used to characterize PAID. The results showed the wight-average weight molecular wight is of 4.45 × 105, and the number average molecular weight of PAID is of 1.91 × 105, the molecular weight distribution index is of 2.3, which indicated the molecular weight distribution was wide. Thermal analysis results showed that PAID had good thermal stability; SEM results indicated that microstructure of PAID solution presented dendritic structure.(2) The comprehensive performance of PAID in based slurr was investigated. The results showed that PAID had good adaptability to large temperature difference cementing.It can not only meet the requiments of thckening time under high temperature, but also can ensure the development of cement compressive strength under low temperature.PAID has satisfied delaying performance and the thickening time is easy to adjust. In addition, PAID has small sensitivity to temperature and content, and it can satisfiy the demands of cementing from 90?180?.What's more, PAID has good compatibility with fluidloss additives and retarders, which is beneficial to improve the fluidity of cement slurry and helpful to control the fluid loss. (3) Zwitterionic retarder containing different cationic monomer were obtained. The chemical oxygen consumption (COD),T2 relaxation time and XRD were used to study the adsorption behavior of zwitterionic retarder on cement particle surface, the early hydration prooerties of cement slurry with zwitterionic retarder and the hydration products of set cement.Based on the above experiments, There are two primary models for cement hydration inhibition of zwitterionic retarder:surface adsorption and calcium complexation.The probable reasons for the adaptation to large temperature difference circumstances of zwitterionic retarder are as follows.1) The formation of loose adsorption layer by zwitterionic retarder is due to its weak adsorption intensity, which make the zwitterionic retarder easy to desorption.The constantly "adsorption-desorption"pocess of zwitterionic retarder is helpful to achieve its retarding action with the continuing hydration reaction.2) Due to the reversible thermo-responsive behavior of PAID, there are big differences of adsorption amount between high and low temperature.Under the high temperature, large amount of retarders adsorbed on the cement and the hydratin inhibition is more intense than that under the low temperature. Which led to the differences of hydration inhibition between high and low temperatue.3) The complexing ability of calcium ion is different between high and low temperature.Under the low temperature, the retarder molecular molecular chain curled up and the partial carboxyl was encased, which led to the low chelating ability of calcium ion and the retarding ability decreased. While under the high temperature,the molecular chain of retader extended, which enhance the chelating ability and hydration retarding. Therefore, the large temperature differences retarding is achieved.(4)The reactive light weight additive names ESC-25 was prepared. The FTIR, EDS, SEM, TG and DSC had been used to characterize ESC-25. Infrared spectrum and energy spectrum analysis results showed that the slag composited with the organic resin matrix successfully; Wetting experiments results showed that slag enhanced the hydrophilicity of resin matrix surface. SEM results suggested ESC-25 had good shearing mechanical properties. Thermogravimetric results indicated that the addition of slag improved the thermal stability of light weight additives. In addition, ESC-25 has good shearing and pressure resistance, which is help to ensure the density stability of cementing slurry in deep well; XRD and TG-DSC experiments testified the activation mechanism of ESC-25.whic is that the pozzolanic reaction of slag by consumption of Ca(OH) 2 to form calcium silicate hydrate (C-S-H) gel which contributed more to the compressive strength of set cement.(5) The hardening accelerator, fluidloss additives and a series of admixtures have been selected out based on the PAID and ESC-25.Finally, the experimental research has developed the new recipe of lighht density slurry system suited to deep wells of high temperature and large temperature difference with low pressure gradient. The test has evaluated the system performance and the results show that its conventional properties can meet requirements and the slurry is stable. The slurry thickening time can be extended to the proper treatment duration and the set cement can develop high strength in early stage in low temperature conditions, which can satisfy the needs of deep well long-term zonal isolation with low pressure gradient.