Development Of Temperature Sensitive Polymer Flow Regulator For Deepwater Drilling Fluid

In deepwater drilling,the drilling fluid viscosity increase rapidly under the environment of low temperature and high pressure.The effect of conventional treatment agent on the low temperature rheological properties of drilling fluid is poor,which leads to the flow resistance of drilling fluid increasing and a series of downhole complex cases such as lost circulation,high equivalent weight and hard pressure control and so on.So the “constant rheological” drilling fluid system has become a new trend,oil-based and synthetic-based drilling fluid developed rapidly because of the low-temperature rheological controlled more easily,it is difficult for water-based drilling fluid to develop,because the viscosity change in the range of 4~65? is obvious.So with the development of deepwater drilling,the rheological regulation problem of deepwater water-based drilling fluid must be solved in the futureIn this paper,based on a large number of literature research,a thermo-sensitive polymer(PVCL),which regulates the rheological properties of deepwater-based drilling fluid system,is prepared.Poly(N-vinylcaprolactam)(PVCL)was synthesized by precipitation polymerization in aqueous solution with azodiisobutyronitrile(AIBN)as initiator and N-vinylcaprolactam(NVCL)as reactants.The optimum reaction conditions were determined by orthogonal monomer:experiment: initiator: solvent is 1:50:500(mass)and the reaction temperature was 55?,the reaction time was 4h;studying the effects of salt concentration,pH value and polymer concentration on the LCST of sample.The thermostable polymer PVCL was characterized by IR,GPC,MS.The experimental results show that the synthesized PVCL has a good resistance to temperature and salt and has a certain rheological regulation ability for the water-based drilling fluid system.The basic formula of the deep water-based drilling fluid system is optimized: 4%bentonite pulp+0.5%XC+0.5%PVCL+4%SD-101+4%SD-201+2%Lubricant+20%NaCl.