Research On Synthesis And Function Of Fluid Loss Additive With High Temperature Resistance

High-temperature resistant water-based drilling fluid is an important fluid of deep well drilling.As a key component of the drilling fluid system,it is crucial to study the high temperature water-based filtration loss additive which directly determines the performance of the drilling fluid.This paper studied filtration loss additive of high-temperature resistant water-based drilling fluid,explored about the mechanism of it and thus supply a technical reference of selection for high-temperature resistant water-based drilling fluid for deep wells.According to theories of molecular structure design,and combining with structural characteristics of high temperature resistant fluid loss additive,siloxane as adsorbing group and sulfonic ashydration group are introduced into molecular of fluid loss additive respectively.One kind of organosilicon quadripolymers(AM/AMPS/NVP/KH570)used as a high temperature fluid loss additive were synthesized by free radical polymerization from acrylamide(AM),2-acrylamido-2-methylpropanesulfonic acid(AMPS),N-vinylpyrro-lidone(NVP),and γ-(methacryloxy)propyltrimethoxysilane(KH570)as the main reaction monomers.The structure of organosilicon fluid loss additive was identified by Fourier transform infrared spectrum(FTIR),and the element analysis showed the composition of synthetic copolymer was in accord with designed copolymer.According to the minimum of American Petroleum Institute filtrate volume andHigh-temperature and High-pressure filtrate volume of saturated brine based drilling fluid with 5,0wt%two kinds of organosilicon drilling fluid loss additives after being thermal aged at 180℃for 16h,Optimum reaction conditions for AM/AMPS/NVP/KH570:n(AM):n(AMPS):n(NVP)=1:2:1,KH570 molar fraction(amount of total substance based on AM,AMPS and NVP)is The mass fraction of 5.0%,and the mass fraction of total monomers(based on the total mass of AM,AMPS,NVP,and KH570)was 10.0wt%.Properties of AM/AMPS/NVP/KH570 synthesized under the optimum synthetic condition were characterized in many ways.The FT-IR was utilized to testify the molecular structure of the polymer coincided with the object design.Thermal Gravimetric Analysis(TGA)was employed to study the polymer’s thermal weight loss to evaluate the thermal stability.It was resulted from the Intrinsic Viscosity and Gel Filtration Chromatography that polymer presented a suitable molecular weight and reasonable weight distribution.The performance of the AM/AMPS/NVP/KH570 copolymer was evaluated.The results of the evaluation showed The polymer was good at filtration loss control and was resistant to temperature at 180℃ and high concentration of calcium and salt.With the increase of polymer concentration,API filtration loss and HTHP filtration loss gradually decreased.When the copolymer concentration was 5.0 wt%,the filtration loss of drilling fluid could be effectively controlled.Increasing the concentration of NaCl in the drilling fluid to saturation or increasing the concentration of CaCl2 to 1.0%has limited impact on the filtration loss performance of the copolymer drilling fluid system.Centered on the AM/AMPS/NVP/KH570 as main filtration loss agent,mixed with other necessary agents,the paper formed a set of water-based drilling fluid resistant to high temperature,salt and calcium and with good inhibition capability.By virtue of SEM,Zeta Potential Analyzer and Particle Size Analyzer and other modern analytical instruments,and through the micromorphology and particle size distribution of clay cake that formed in the drilling fluid,this paper studied the mechanism of the organosilicon polymer in drilling fluid.The results illustrated that the capabilities of temperature resistance and adsorption performance of polymer fluid loss additive are excellent.SEM was utilized to study the AM/AMPS/NVP/KH570 about the morphology of clay cake.The result of SEM showed that the polymer fluid loss additive can significantly improve the quality of the clay cake and and reduce the loss of the drilling fluid at both fresh water,salt water and calcium base fluid.Through the clay particle size distribution analysis,it is proved that the hydration dispersion of clay particles are ensured by the adsorption of polymer while it was added into it,resulting in widening of the particle size distribution of the drilling fluid system,the optimization of particle size distribution,improvement of mud cake quality and reduction of filtration loss.