Study On Organosilicate Polymer As High Temperature Resistent Inhibitor For Water-based Drilling Fluids

According to the statistics of the US Energy Information Administration（EIA）,70%of downhole complex accidents in global oil drilling engineering are related to wellbore instability,and 90%of wellbore collapse accidents occur in shale formation.Wellbore instability has always been one of the difficult problems in petroleum drilling engineering.It is urgent to develop a new water-based drilling fluid with high temperature resistance and strong inhibition to solve this technical problem.In this paper,aiming at the problems of single function,insufficient temperature resistance and limited inhibition ability of the commonly used water-based drilling fluid inhibitors,the molecular structure of new organosilicate polymer inhibitors is designed.Based on the performance requirements of high temperature resistance and strong inhibition of water-based drilling fluid,the bonding type,functional group type and molecular weight distribution of polymer inhibitors are optimized a new type of organosilicate polymer ADMOS with film-forming properties is developed by introducing organosilicon functional groups into the side chain of the polymer（1）Emulsion polymerization is used to introduce organosilicon functional groups into polymer inhibitor side chains to solve the problem of hydrolysis of organosilicon monomers in the synthesis of aqueous phase,and ADMOS is synthesized.The molecular structure of ADMOS is characterized by Fourier transform infrared spectroscopy,nuclear magnetic resonance spectroscopy,thermogravimetric analysis,elemental analysis,gel chromatography and X-ray energy spectrum.The experimental results show that ADMOS achieves the key points of molecular structure design of the new shale inhibitor,with a weight average molecular weight of 3994 and good thermal stability;（2）The inhibition performance of ADMOS at room temperature and high temperature is systematically studied through laboratory simulation experiments such as linear expansion,rolling recovery of cuttings and inhibition of pulping.The experimental results show that ADMOS has strong inhibition in the temperature range from normal temperature to 150℃,and has the functions of viscosity increasing,film forming and fluid loss reducing,which provides experimental basis for the construction of high temperature resistant and strong inhibition water-based drilling fluid system;（3）X-ray diffraction analysis,high temperature adsorption experiment,²⁹Si NMR,TG-FTIR and dynamic contact angle are used to reveal the mechanism of ADMOS as a new high temperature resistant inhibitor:ADMOS and Si-OH on the surface of clay minerals formed chemical adsorption through Si-O-Si bonding,and the adjacent layered clay card structure is firmly bound together,which enhanced the adsorption stability of the inhibitor in high temperature environment The hydrophobic film formed on the clay surface can improve the wettability of API filter cake and shale surface,effectively prevent the free water molecules in water-based drilling fluid from invading into the interlayer of clay minerals,and inhibit the hydration expansion and dispersion of clay minerals.（4）The high temperature（150℃）resistant water-based drilling fluid system with ADMOS as the core is constructed.In this system,the rolling recovery rate of cuttings is96.65%,and the linear expansion rate of artificial core is 3.38%.It has a good ability to inhibit the hydration dispersion and expansion of clay,and has the functions of antipollution,fluid loss reduction,improving compressive strength and plugging micro fractures of shale.