Performance Of Polymeric Drilling Fluids Based On Acrylamide-Styrene Sulfonate-Acryloyloxyethy Trimethyl Ammonium Chloride Copolymers

With the increase of global energy consumption and the development of drillingtechnology, exploration and development in oil-gas field is gradually changed fromshallow department stratum to deep department stratum and turned from shallow seato deep sea. Making deep and ultra-deep drilling wells became one of the importantaspects of the petroleum industry in the world. Consequently this leads to higherrequirements for drilling fluids with high filter loss control and high salinity andtemperature resistance.As water-based drilling fluid, acrylamide polymer drilling fluid is most widelyused in oil field development, but it has many drawbacks, such as poor shearingstability, high sensitivity to salt and poor temperature stability. So we attempt to adoptmodification of the water-soluble polyacrylamide to improve its properties.This article attempts to use, acrylic amide (AM), sodium 4-styrenesulfonate(SSS)and acryloyloxyethyl trimethyl ammonium chloride (AETMAC) as comonomers,ammonium persulfate as initiator to synthesize water soluble AA/SSS/AETMACcopolymers by solution copolymerization .Effects of monomers amount, initiatoramount , polymerization reaction temperature and inorganic salt concentration(NaCl,CaCl2)on the polymeric solution performance (reduced viscosity), andpolymeric drilling fluid performance (apparent viscosity, plastic viscosity and filterloss )were systematically investigated. The temperature-resistance and salt-resistanceof polymeric drilling fluids are systematically studied. Structure and temperaturestability of the polymers were characterized by FTIR and TGA. Morphology of thedrilling fluids filter cake was observed by SEM. Water soluble polymer drilling fluidswith high temperature-resistance and salt-resistance and low filter loss was obtainedand the main research results are as follows:(1)Effects of copolymer addition, initiator amount , polymerization reactiontemperature on reduced viscosity and rheological properties of the polymeric drillingfluid were investigated. Polymeric drilling fluid has good overall properties with 0.3% copolymer added, reaction temperature of 75℃and 1.5% initiator .(2)Effects of amount of cationic monomer(AETMAC) and anionicmonomer(SSS) on reduced viscosity and rheological, filter loss , temperature- andsalt- resistance of the polymeric drilling fluid were investigated. Reduced viscosity ofthe polymeric solution can be enhanced by way of increasing AETMAC and SSSamount within a certain range. Polymeric drilling fluid has good rheologicalproperties, low filter loss and high temperature- and salt- resistance when the massratio of AETMAC to SSS deviates from 1:1.(3)Rheological properties of the polymeric drilling fluid, such as apparentviscosity, plastic viscosity and dynamic shear did not change very much withtemperature increase, an indicative of small temperature sensitivity good temperatureresistance.(4)SEM data indicated that the filter cake of the polymeric drilling fluid wasthin and compact. Therefore permeability and filter loss of the filter cake were theeffectively decreased.(5)FTIR spectra showed the characteristic absorption peaks assigned to theamide group, phenyl group, ester group and quaternary ammonium group, anindicative of the structure of AA/AM/DAC copolymers.(6)TGA showed the onset decomposition temperature of the copolymer wasabove 250℃.So the copolymer has high thermal stability.