Development And Mechanism Study On High Performance Polyamine Inhibitor In Water-Based Drilling Fluid

At present, the problem of wellbore stability resulting from shale hydration in complexformations is prominent in the process of land and ocean drilling in our country, whichdirectly affects the safety, quality and benefit of oil and gas engineering, even determining thesuccess of drilling. Therefore it is urgent to develop a new generation of shale inhibitor andhigh performance water-based drilling fluid, which is also an international hot topic. Aimingat the technical difficulty of wellbore instability because of shale hydration, novel highperformance polyamine inhibitor was developed with optimized method based on theprinciple of molecular structure optimization and design. The mechanism of polyamineinhibitor was studied, which enriched the basic theory of wellbore stability and technicalstrategy of inhibitive drilling fluids.The molecular structure of high performance polyamine inhibitor was optimized basedon molecular structure design criteria. High performance polyamine inhibitor SDJA wasdeveloped with two-step method and synthesis optimization experiment. The results ofmolecular structure characterization and inhibitive experiments indicated that, compared toconventional shale inhibitors, the novel non-ionic high performance polyamine inhibitorSDJA with low molecular weight was highly inhibitive, effective for a long term at relativelylow concentration, closing to that of typical foreign product, which provided the key additivefor high performance water-based drilling fluid system.The micro-mechanism of high performance polyamine inhibitor SDJA was studied viaFT-IR, XRD, Zeta potential measurement, TGA and contact angle test and so on. The resultsindicated that, the non-ionic high performance polyamine inhibitor with low-molecularweight becomes positively charged after protonation in aqueous solution. Therefore it isadsorbed onto the negative surface of clay with electric attraction and hydrogen bonding. Hydrated cationic ions in the interlayer of clay are exchanged, resulting in the drop ofelectrostatic repulsion between clay surface and repulsion between hydration shells on theclay surface. Because of multi-amine groups of polyamine, multi-adsorption betweenpolyamine and clay surface occurs, which binds the adjacent clay layers together and leads tothe formation of contact structure. Meanwhile polyoxypropylene chain of polyamine coversthe surface of clay, forming a hydrophobic barrier, which hindering clay hydration effectively.It’s difficult for polyamine to desorption, thus it can stabilize shale with a long term.Protonation of polyamine will be improved after reducing the pH value of medium properly,contributing to the inhibition of shale hydration and wellbore stabilization.Based on the newly developed high performance polyamine inhibitor, two polyaminehigh performance water-based drilling fluids with low clay content and clay free wereestablished, respectively. The inhibitive and lubricant properties are equal to that of oil-baseddrilling fluid. The two systems are also rheology excellent, pollution resistant, lowbiologically toxic and environmental friendly. Furthermore, evaluation methods includingbulk hardness test were established to evaluate the properties of polyamine high performancewater-based drilling fluid.The industrial pilot production and field application test of high performance polyamineinhibitor SDJA were carried out with great success. The results indicated that the newlydeveloped high performance polyamine inhibitor was compatible with various fluids,improving the inhibition of drilling fluid significantly. Wellbore stability of shale formationwas enhanced obviously, meeting the requirement of drilling engineering.