Synthesis And Evaluation Of Cationic Hydrophobic Shale Inhibitors

In the process of drilling in the world,we often encounter water sensitive formation,mud shale hydration expansion of the formation will lead to complex drilling accidents,such as wellbore collapse,instability and stuck drill.Oil based drilling fluid is more effective in solving this problem,however it is difficult to deal with waste rock,which is easy to cause environmental pollution,a high cost and not be conducive to improve drilling speed,thus it is necessary to improve the inhibition of the water-based drilling fluid.Water based drilling fluid mainly relies on the shale inhibitor to play a role in inhibiting shale hydration expansion,Among them,the organic cationic shale inhibitor is one of the main inhibitors to improve the inhibition of water-based drilling fluid and inhibit the hydration expansion of shale,it plays an important role in reducing the probability of underground complex situation.In this paper,a low molecular weight cationic poly(acrylamide),i.e.,BJX-1,with hydrophobic units was prepared by precipitation polymerization,as a shale inhibitor.Acrylamide(AM),methacryloxyethyl trimethylammonium chloride(DMC),and octadecyl acrylate(SA)were selected as the monomers.The single factor method was used to optimize the synthesis conditions,the optimum reaction conditions were ascertained as follows:anhydrous ethanol as solvent,reaction temperature was 80 ?,reaction time was 5h,the mass fraction of the initiator was 0.5%,the monomer mass fraction was 3%,and AM was 60%,DMC was 38%,SA was 2%.In these conditions,we can obtain an inhibitor which recovery rate can reach 90.37%with a weight average molecular weight of 1.52×1 05g/mol.FT-IR,1HNMR,thermogravimetric analysis were used to characterize the structure of the polymer.Using "pyrene" as a fluorescent reagent,the fluorescence spectrophotometry was used to demonstrate that the polymer could form a hydrophobic microdomain.The shale recovery,relative inhibition rate,linear expansion rate and inhibition of bentonite slurry were evaluated,the results showed that with the increase of the amount of inhibitor,shale recovery and relative inhibition rate increased,indicating the more obvious inhibitory effect;and BJX-1 showed better inhibitory effect than other types of inhibitors,and the optimum dosage was 1%;BJX-1 can make the linear expansion rate greatly is reduced,and basically stable after 8h.With good inhibition of bentonite slurry performance,can increase the amount of bentonite to 35%.Evaluate the temperature resistance and salt resistance of BJX-1,the results showed that BJX-1 has good temperature resistance,can reach 120 ?,and can be well compatible with inorganic salts,had good salt resistance.In addition,the drilling fluid compatibility with BJX-1 and filtrate loss results showed that BJX-1 can not only improve the rheological property of drilling fluid,the drilling fluid rheology is more stable,but also had very good filtrate loss.Dispersed in different solvents,contact angle and SEM were measured,and the results showed that after BJX-1 treatment,the surface wettability of cuttings and bentonite will be changed,especially in the picture of SEM,we can see smooth structure like membrane.Zeta electric potential and interlayer spacing of BJX-1 also were measured,the results showed that the cation structure of BJX-1 can be adsorbed at the surface of clay particles by electrostatic attraction,and neutralize the negative charge of clay particles,so that the absolute value of Zeta potential of clay particles and the interlayer distance of clay decreased.