Preparation And Performance Evaluation Of Crosslinking Acid-nanoparticle Composites

Acid-fracturing is one of the most important measures to keep and increase output of carbonate reservoir.But during the acid-fracturing process of deep and ultra-deep carbonate reservoir,the general crosslinking acid has poor properties of heat and shear resistance,and short crosslinking time,which make the acid system sheared in the tubing for too long time and the viscosity of the acid system in the formation too low.That influences the effect of acid-fracturing construction greatly.The paper aims at developing a novel crosslinking acid system,which possesses good heat and shear resistance,and property of delayed crosslinking.That settles a series of problem of the acid-fracturing of the deep and ultra-deep carbonate reservoir.After the optimal experiment,the type and dosage of acid and thickener are identified.A novel kind of organic zirconium crosslinker JLJ-11 is developed,which is synthetized with zirconium oxychloride,polyols,amine and hydroxycarboxylic acid.Crosslinking time and gel strength are taken as evaluation indexes,and the preparation technology of JLJ-11 is optimized.The optimum reaction condition is: the mass ratio of water,hydroxycarboxylic acid B,amine A,zirconium oxychloride and polyols F is 1:1:2:2:3,the reaction time is 3 hours,the reaction temperature is 70℃.On the basis of optimized thickener and crasslinker,other additives are added into the acid system,and their type and concentration are optimized.And then we get the basic formula of the novel crosslinking acid: 0.8% thickener FS3802 + 1.0% crosslinker JLJ-11 + 2.0% corrosion inhibitor HJF-10 + 1.0% ferric ion stabilizer TWJ-10 + 1.0% cleanup additive CF-5A + 0.1% gel breaking agent PC330.On the basis of the novel crosslinking acid,and to further develop the heat and shear resistance of the acid system,the nano-silica is mixed with the acid system,and the crosslinking acid-nanoparticle composites is obtained.After the optimal experiment of nano-silica,the hydrophilic fumed silica of HDK? T30 is chosen,and its best dosage is 0.5%.The influence of nano-silica on heat and shear resistance,and delayed crosslinking properties,is studied.The results show that,though the nano-silica has no effect on delayed crosslinking properties,it observably enhances heat and shear resistance of the composites.The crosslinking acid-nanoparticle composites remains above 50mPa·s,even though the acid gel has been sheared for more than one hour under the shear rate of 170s-1 and at the temperature of 150℃.Referring to the professional standard,comprehensive performance evaluation of the crosslinking acid-nanoparticle composites is made.The results show that,this composite acid system has good compatibility,exellent sand-carrying ability,small filter loss and high corrosion coefficient,good property of delaying acid-rock reaction speed,gel breaking completely and low glue residue.It is concluded that the composite acid system can meet the requirement of acid-fracturing operation.