适用于深层煤岩气水平井的新型井壁稳定剂OA

A borehole wall stabilizer WDJ-1 was developed to address the problem of borehole wall instability and sloughing caused by property differences at the interface of coal-rock and coal-gangue in horizontal wells for deep coalbed methane(CBM).WDJ-1 was synthesized via aqueous solution polymerization using polyvinyl alcohol(PVA)and tannic acid(TA)as functional monomers,and borax and ferric chloride(FeCl3)as dual crosslinking agents.The synthesis was optimized with a monomer ratio of PVA∶TA=1∶1,a reaction temperature of 85℃,a reaction time of 3 h,a system pH of 7.5,and the concentrations of the crosslinking agents(0.1%borax and 0.25%FeCl3).The structure of WDJ-1 was characterized by Fourier-transform infrared(FT-IR)spectroscopy,scanning electron microscopy(SEM),and thermogravimetric analysis(TGA),and its performance was evaluated through rheology,plugging capacity,cementation property,and inhibition property experiments.FT-IR confirms the presence of O—H,C=O,B—O,and Fe—O coordination bonds in the molecules of WDJ-1,indicating sufficient reaction between the monomers and the crosslinking agents.SEM reveals that WDJ-1 exhibits a honeycomb structure,which can improve the compactness of the mud cake.A base fluid treated with 2%WDJ-1 has its API fluid loss reduced from 22.4 mL to 3 mL,the shear strength of the coal rock-coal gangue interface reaches 0.16 MPa,the plugging pressure for a 2 mm slot plate increases by 54.5%,and the 48-hour water absorption rate of mud balls is reduced by 10.5%.TGA measurement proves that WDJ-1 exhibits excellent thermal stability below 240℃.WDJ-1 stabilizes wellbore through the four-fold synergistic mechanism of"inhibition-plugging-bonding-high temperature resistance",and the use of which can provide technical support for the safe and efficient drilling of horizontal wells in deep CBM reservoirs.