Synthesis And Formulation Of Electrically Attracting Associative Polymer Fracturing Fluid Thickeners

The fracturing fluid has been widely used and developed in the development of oil and gas fields.As the working medium of hydraulic fracturing,fracturing fluid is becoming more and more important,as well as the thickening agent of fracturing fluid.The thickening agent which is currently used,neither the plant gum or VES has its shortcomings,so this paper used the method of artificially synthesis to get a new kind of polymer thickening agent,and come up with a new crosslinking mode——molecular association of electric attraction,and study on the formula of fracturing fluid and mechanism of vicosifying action based on the new theory.The thickening agents used most in current time are plant gum,VES,and the polymer which uses chemical crosslinking,but these three type of thickening agents all have disadvantages,such as the palnt gum's high amount of residue,the poor high-temperature resistance of VES,and the high friction drag of the chemical crosslinked polymer.According to these disadvantages,this paper developed a new kind of thickening polymer agent and fracturing fluid system,which uses the molecular electric attraction to tackify.The thickening agent has many advantages,such as lower residues,and damage ratio of core sample,besides,the synthesis method is simple and easy,the raw materials are easy to get and cheap.The polymer's raw materials are AM and DMDAAC,the initiating system is complex initiation system which includes oxidation-reduction initiator system and azoic compound,and the synthesis method is aqueous solution polymerization.This paper has investigated the influence factors to this synthesis process by single-factor experiments,such as the monomer mass fraction,monomer molar ratio,reaction temperature,initiation system's mass fraction,pH of the system,the mass fraction of crosslinking resistant agent and solubilizer,the time and temperature of drying and so on.Confirm the polymer's best molecular weight and cationic degree by the test of polymer's effect before and after crosslinking.At last the best synthesis condition was decided by orthogonal experiment.Test the polymer's solution rate and tackify effect by experiments,according to the test results,the polymer has a good high-solubity and tackifying effect.This paper also discussed the polymer's IR spectrum and nuclear magnetic resonance,which comfirmed that the synthetic polymer is the target product.The formula of this fracturing fluid system is chosen by tests,which is conducted according to the Chinese Standard of Oil and Gas SY/T 6074-94 and SY/T 6214-1994,and also evaluated this fracturing fluid by the standard of SY/T 6376-2008,SY/T 5107-2005,SY/T 6296-1997,and some standards of relevant enterprises.All the tests proved that the fracturing fluid can meet the standards and the requirements of fracturing operation.Testing the surface tension,Zeta potential and the molecular particle size of polymer solution with different surfactant's fraction,and comparing them with solution viscosity——surfactant fraction curve,and analyze the tackify mechanism by the curves.According to the analysis,the surfactant molecules first become micelles in the polymer solution,which leads surfactant molecules begin to attach to the polymer molecular chains,which can build a space grid structure to tackify,and the surface tension and Zeta potential of solution almost remain the same.When the viscosity of the solution gets the highest point,its Zeta potential absolute value also reaches its highest point,which indicates that the solution.system is most stable.In the mean time,the molecular particle size rises obviously.When the amount of surfactant is higher than best value and keep increasing,the surfactant molecules attached to the polymer molecular chains will still rising,which changes the electrostatic attraction to electrostatic repulsion,so some of the space grid structure will be destroyed,and the viscosity of solution decreases.Meanwhile,the Zeta potential turnsto negative,the surface tension remains still,and the molecular particle size keep increasing slowly.What's more,by analyzing the IR spectrum and 1H-NMR of the polymer thickening agent,the crosslinked fluid and the gel broken fluid,we confirmed that the tackify mechanism is physical crosslinking rather than chemical crosslinking.At last,explain the electric attraction association between polymer thickening agent and surfactant by micro-modelling,which describes this tackify process vividly.