Preparation Of Graft-Modified PB Latex And Its Applied Research In Oilwell Cement

The petroleum exploration gradually developed to the complex strata,causing the environment in bottom hole more complex,and cementing difficulty is further increased.The use of oil cement alone can not meet the needs of cementing conditions,therefore,it is necessary to add some admixtures?including organic materials,polymer materials,inorganic materials or composites?to the well cement to improve the performance of the cement slurry and the cementing quality,drilling efficiency,crude oil production and extend the life of oil wells.In order to solve the problem of poor salt resistance and freeze-thawing stability,bad toughening ability and poor integrated performance of cementing latex,this study used the molecular design principles and emulsion polymerization methods in this paper.The Styrene?St?,2-acrylamido-2-methylpropanesulfonic acid?AMPS?and N,N-Dimethylacrylamide?DMAA?as a modified functional monomer were grafted onto the seed emulsion polybutadiene?PB?,by selecting the optimum ingredient and synthesis process of polymers,a new-style latex HTL-100L was finally developed,which had well comprehensive properties.HTL-100L was analyzed by means of infrared?IR?,nuclear magnetic resonance?NMR?,thermogravimetric analysis?TG?,particle size analyzer and transmission electron microscopy?TEM?in this study.The results showed that the synthesized latex contained all the monomer structures involved in the polymerization,and the HTL-100L was the target product.The molecular structure was stable at high temperature about 420?.The average particle size was 207 nm.From the TEM images,it was clearly observed that HTL-100L had a core-shell structure.The solid content and viscosity of HTL-100L were 32%and 25 mPa·s,the chemical stability and mechanical stability were qualified,and the appearance was micro-blue light white emulsion.The test results of cement slurry with HTL-100L showed that HTL-100L had well salt-resistant stability and could be used in salt water slurry system cementing.The freeze-thaw stability had been significantly improved,the rheology and stability of cement slurry of HTL-100L had been also improved,and the water loss of the cement slurry was reduced.In addition,the HTL-100L enhanced the flexural strength and improved the late compressive strength decline of the cement stone.Cement stone strength developed well within 24 hours and the elasticity modulus was low which significantly improved the toughness of cement stone.The thickening curve of cement slurry with HTL-100L was smooth,the transition time was short and approximatly right angle thickening.It was suitable for wide temperature range?80-180??that could be used with other admixtures in high temperature.The mechanism of the latex in cement slurry was explored by means of cement hydration heat analyzer,X-ray diffraction?XRD?and scanning electron microscopy?SEM?.The results showed that HTL-100L had weak retardation which could inhibit the formation of cement hydration products Ca?OH?₂ and the higher the amount of latex was,the inhibition was stronger.The formation of the polymer film and the latex particles into the pores of the filter cake blocked the channels causing water loss in cement slurry,so improved the performance of water loss in cement slurry.The formation of interpenetrating and interweaving mesh structure and the polymer film in cement enhanced the toughness of the cement stone.