Preparation And Properties Of Cs-AM-KH Composite Graft Copolymer As Filtrate Reducing Agent

Starch is a renewable bioresource with abundance and low price.Modifications such as etherification,crosslinking and grafting endow the starch with good salt resistance and filtration loss reduction performance,which result in a wide utilization of midified starch as drilling fluid filtrate reducing agents to reduce the drilling fluid pollution toward the oil reservoirs.Grafted copolymer starch is a kind of copolymer that is formed by grafting monomer onto starch molecule under the initiator.The grafted copolymer starch with a improved resistant temperature is a promising candidate of filtrate reducing agent with good salt resistance.Two kinds of grafted starch copolymer filtrate reducing agents,cassava starch/acrylamide(binary copolymer,Cs/AM)and cassava starch/acrylamide/?-methacryloxypropyltrimethoxysilane(ternary copolymer,Cs/AM/KH),were synthesized by graft copolymerization.This reaction was conducted in the aqueous environment containing a oxidant reduction initiation system(NH4)2S2O8 and NaHSO3).The effects of the pH of the reaction system,the concentration of total reactants,the amount of monomer,the amount of initiator,the reaction time,and the reaction temperature on the filtrate volume of the product were investigated.The result showed that the binary copolymer revealed a favourable performance when it was prepared under the conditions of the total reaction material content 20%,the reaction temperature 50 ?,the mass ratio of starch to AM 1:2,the amount of initiator 1%,the reaction time 3 h.While the ternary copolymer showed a performace of filtrate reducing when it was produced in the conditions of the reaction solution pH 4,the reaction temperature 50 ?,the AM dosage 200%,the KH570 dosage 30%,the initiator dosage 1%and the reaction time 3 h.The techniques such as fourier infrared spectrometer(FTIR),thermogravimetric-differential scanning calorimetry(TGA-DSC),thermogravimetric-infrared spectroscopy(TGA-FTIR),X-ray diffractometer(XRD)were used to characterize the molecular structure,crystal structure and the thermal stability of the both binary copolymer and ternary copolymer.The results indicated that these copolymers with excellent thermal stability were successfully prepared.The properties of Cs/AM and Cs/AM/KH were evaluated by rheological tests and filtrate reducing experiments,respectively.The results showed that the drilling fluid containing a suitable dosage of Cs/AM(1.5?3.5 wt%)with a good NaCl resist even in saturation and a heat-resistant to 120 ? presented a good filtrate reducing performance under normal temperature.While the the drilling fluid that contained an appropriate amount of the aged Cs/AM/KH(2.0-4.0 wt%)showed a preeminent filtrate reducing performance,a good NaCl-resistant resist to the saturation and a heat-resistant to 180?.The Cs/AM and CS/AM/KH were mixed to form the composite of filtrate reducing agent.The drilling fluid that contained both Cs/AM and CS/AM/KH(1.5 wt%and 3.5 wt%,respectively)presented a preeminent filtrate reducing performance,a good NaCl-resistant resist to the saturation and a heat-resistant to 180 ? under both fresh and aging conditions.This work provides basics of experiment and theory for the further processing technology of cassava starch of Guangxi and the development of green filtrate reducing agent.