Study Of Acrylamido-polyampholyte As Fluid Loss Reducer Resistant To High Temperatures And High Salinities

As the proportion of oil and gas resources in deep strata and deep water grows,drilling becomes more difficult and requires drilling fluids resistant to high temperatures and high salinlities.Among additvies of water-based drilling fluids,effective fluid loss reducers able to endure 180? and saturated NaCl have always been an engineering challenge which needs to be solved APSP.This paper assumed that cationic groups,as the adsorption groups in polymer chains,can improve not only the stability of polymer's adsoprtion onto bentonite but also the ability of filtration controlling.The ability to withstand high temperatures and high salinities,to adsorp on clay,to maintain particle size distribution of salt-water mud and reduce filtraion of hydrolyzed polyacrylamide with cationic groups and its derivatives,were studied in this paper in order to verify the assumption that cationic groups can improve the adsorption and filtrate controlling ability of polyampholyte.AM,DMDAAC and AMPS were polymerized to synthesize polymers in this paper.A series of polyampholytes,namely HPAD and HPADA,were synthesized with varied structual parameters including cationicity,anionicity and intrinsic viscosity.IR and 1H NMR were used to characterize the molecular structure of HPAD and HPADA.Titration,element analysis method and Ubbelohde capillary viscometer were used to calculate the structural parameters.ESEM analysis of polyampholyte aqueous solutions' microstructure showed that increasing anionicity leads to a higher degree of curling of molecular chains;TGA data revealed that polyampholytes synthesized were able to edure high temperature no less than 200? and growing anionicity had a positive effect on the thermal stability of molecular chains.Solution viscosity dropped drastically,then changed a little and even rebounded,as the concentration of NaCl kept growing in polymer aqueous solution.NaCl benefits polyampholyet's adsorptivity.Oxygen does great harm to polyampholyte's thermal stability under high temperatures and in aqueous solution.Na2SO3 of 1 wt%can not only protect polymers from the harms of high temperatures,but also effectively cut down HTHP filtration of saturated salt-water mud with polyampholyte.This paper investigated the influence of structural parameters on polyampholyte's adsorptivity on bentonite under varied temperatures.Cationicity of more than 10 mol%,intrinsic viscosity of more than 300 mL·g-1 and anionicity about 30 mol%increased polymer's adsorbance under varied temperatures,which reveals that cationic groups can guarantee the adsorption of polyampholyte on clay under high temperatures.This paper also investigated the influence of structural parameters on polyampholyte's ability of maintaining particle size distribution and filtration controlling,as well as the macrostructure and microstructure of HTHP filter cakes.An ideal molecular model of polyampholyte filtration controller was proposed,which includes high cationicity(10-15 mol%),high intrinsic viscosity(400-600 mL·g-1)and anionicity in a proper range(40-45 mol%).According to the ideal molecular model,a new polymerization method of AM and DMDAAC was proposed with optimized reaction condition as following:redox initiators of"MnCl2-O2-NaHSO3";MnCl2:NaHSO3=1:1;the proportion of initators was 0.08 wt%of monomers' weight;the proportion of monomers was 25 wt%of the whole reaction system's weight;free radical polymerization in aqueous solution;30? as reaction temperature;8 h as reaction duration.AM/DMDAAC dipolymer with cationicity of 11.26 mol%and intrinsic viscosity of 485.61 mL·g-1 was synthesized,which met the demands of ideal polymer model.Its hydrolysate of 3.5 wt%can reduce the HTHP filtration(180?)of saturated salt-water mud to less than 10 mL after hot rolling under 200?.A comparison of performance in adjusting particle size distribution controlling and filtration reduction among HPAD,SMP-?,Driscal and Dristemp,was conducted to evaluate which chemical additive is more suitable for being as fluid loss reducer in saturated salt-water mud.The outcome of tests above demonstrated that HPAD peformed better as filtration controller than its domestic and overseas counterparts under 180? and saturated NaCl.