Study On Synthesis Of Water-soluble Novolak Resin And Its Property Of In-depth Profile Control Of Reservoir

In order to meet the needs of new profile control agent for the reservoirs in offshore oil field of South-east Asia,water-soluble Novolak resin(a new profile control agent)was synthesized by acid catalytic reaction through changing synthesis conditions based on the research of water-soluble Resol resin.Molecular structure of water-soluble Novolak resin was characterized by FT-IR,HPLC/MS technology.Aggregation behavior of the resin molecules was studied by Dynamic Light Scattering(DLS)measurement.Surfactants of Tween 60 and dodecyl benzene sulfonate(SDBS)were mixed with water-soluble Novolak resin,and the effects of Tween 60 and SDBS on aggregation rate,surface potential,strength and disassemble/reversibility of Novolak resin molecular aggregates were evaluated.Membrane filtration,core plugging and core oil displacement experiments were conducted to evaluate the blocking,in-depth migration and oil displacement abilities of water-soluble Novolak resin.Experimental method and device were established for measuring diffusion rate of NaCl in core porous media,and the diffusion rate of NaCl was measured and calculated.The main results of this study are as follows:1.Synthesis conditions of water-soluble Novolak resin is : molar ratio of formaldehyde/phenol 0.85;acid catalytic reaction conditions: pH of reaction fluid 1.0,reaction temperature 90~95?,reaction time 120~140 min;methylation reaction conditions: reaction temperature 90~98?,reaction time 60~90min,pH of reaction fluid 11~12.2.The degree of polymerization of water-soluble Novolak resin is 2~10,relative molecule mass is 200~1200,and phenolic rings are linked by methylene via para-para and ortho-para positions.Compared with water-soluble Resol resin,the quantity of hydroxymethyl on water-soluble Novolak resin is significantly decreased.The water-soluble Novolak resin could be stored for more than 240 days at 40?.3.Water-soluble Novolak resin is stable in deionized water and low salinity water with low aggregation degree,and the surface charge of the molecules or molecular aggregates is negative.The electrostatic repulsion between the molecules or molecular aggregates is the main reason for stabilizing the dispersion.Increasing electrolyte concentration and decrease solution pH lead to the increase of aggregation rate.Molecular aggregates have disassemble/reversibility property,as well.4.Tween 60 is able to decrease aggregation rate,increase dispersion stability,decrease aggregates diameter and decrease aggregation strength of water-soluble Novolak resin molecular aggregates by steric hindrance effect.With addition of SDBS,the hydrophobic association effect can be enhanced,which leads to the promotion of molecular aggregation,increase of aggregation rate,decrease of dispersion stability and increase of molecular aggregates size.However,the aggregation strength is not changed obviously.5.For in-depth profile control of the reservoir with medium-low permeability and long well spacing between injectors and producers,a low salinity water slug can be injected before and after the profile control agent(water-soluble Novolak resin)slug to prevent the aggregation of the resin molecules.In this way,the profile control agent with low viscosity can be injected into deep of reservoir easily.6.Comparing with water-soluble Rosel resin,high temperature tolerance ability of water-soluble Novolak resin is enhanced.The water-soluble Novolak resin molecular aggregates have better plugging,migration and oil displacement property in core,and it can be used as a profile control agent in South-east Asia offshore oil field.