Abstract
As an important industrial material, bentonite has been widely applied in water-based drilling fluids to create mud cakes to protect boreholes. However, the common mud cake is porous, and it is difficult to reduce the filtration of a drilling fluid at high temperature. Therefore, this paper endowed bentonite with a thermo response via the insertion of N-isopropylacrylamide (NIPAM) monomers. The interaction between NIPAM monomers and bentonite was investigated via Fourier infrared spectroscopy (FTIR), isothermal adsorption, and X-ray diffraction (XRD) at various temperatures. The results demonstrate that chemical adsorption is involved in the adsorption process of NIPAM monomers on bentonite, and the adsorption of NIPAM monomers accords with the D–R model. With increasing temperature, more adsorption water was squeezed out of the composite when the temperature of the composite exceeded 70 °C. Based on the composite of NIPAM and bentonite, a mud cake was prepared using low-viscosity polyanionic cellulose (Lv-PAC) and initiator potassium peroxydisulfate (KPS). The change in the plugging of the mud cake was investigated via environmental scanning electron microscopy (ESEM), contact angle testing, filtration experiments, and linear expansion of the shale at various temperatures. In the plugging of the mud cake, a self-recovery behavior was observed with increasing temperature, and resistance was observed at 110 °C. The rheology of the drilling fluid was stable in the alterative temperature zone (70–110 °C). Based on the high resistance of the basic drilling fluid, a high-density drilling fluid (ρ = 2.0 g/cm3) was prepared with weighting materials with the objective of drilling high-temperature formations. By using a high-density drilling fluid, the hydration expansion of shale was reduced by half at 110 °C in comparison with common bentonite drilling fluid. In addition, the rheology of the high-density drilling fluid tended to be stable, and a self-recovery behavior was observed.
Highlights
As an important industrial material, bentonite has been widely applied in agricultural, medical, and energy fields for decolorization, suspension, and stabilization [1,2,3]
Bentonite was modified with NIPAM monomers to temporarily plug water-based drilling fluids at high temperature
Chemical adsorption was involved in the process of bentonite adsorption of NIPAM monomers due to the function of hydrogen bond and cations exchange, and NIPAM
Summary
As an important industrial material, bentonite has been widely applied in agricultural, medical, and energy fields for decolorization, suspension, and stabilization [1,2,3]. This significantly theattempt difficulty and canwater even molecules cause drillinbit sticking and[9,10,11] Incan contrast, in this increase paper, we to and cost of drilling with the increase of the viscosity of the fluid and can even cause drill bit sticking reduce the water loss by modifying bentonite and tuning the response of the mud cake to and borehole Via collapse. Found in the filtration, plugging, and rheology of modified plugging,The andself-recovery rheology of behavior modified was drilling fluid, which showed great potential for exploring shale drilling fluid, which showed great potential for exploring shale oil/gas at high temperature
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