Hydrophobically modified low molecular weight polymers as high temperature resistant shale inhibitor

•A hydrophobically modified low molecular weight anti-high temperature shale inhibitor (SDY) was developed.•The hydrophobically modified SDY can adsorb on the shale surface to make its wetting reversal.•SDY molecules can enter between clay layers to inhibit the hydration of clay.•SDY showed better inhibition performance than existing inhibitors at high temperature. With the exploration and development of deep oil and gas, an efficient shale inhibitor resistant to high temperatures is critical for wellbore stability during drilling. In this paper, a hydrophobically modified low molecular weight polymer (SDY) is studied to maintain wellbore stability at high temperatures during drilling. The inhibition performance of SDY was investigated using linear swelling experiments and rolling recovery experiments at different temperatures. The experimental results showed that SDY had good inhibition performance. At 150 °C, the expansion rate was 61.69 % for 1 % SDY and 175.51 % in water. And the rolling recovery of shale rock chips was 87.53 % for 1 % SDY and 18.92 % in water. Compared with water, it can reduce the hydration swelling rate of bentonite rock mold by 57 % and improve the recovery rate of shale rock chips by 3.37 times at 150 °C. The inhibition mechanism of SDY was analyzed by zeta potential, particle size distribution, contact angle, self-absorbing water, X-ray diffraction and scanning electron microscopy experiments. The good inhibition performance of SDY at high temperatures may be attributed to three aspects. First of all, SDY molecules can neutralize the negative charge on the shale surface by electrostatic effect, and reduce the repulsive force between shales to inhibit the hydration dispersion of shales. Second, SDY can still adsorb on the shale surface at high temperatures to form a hydrophobic film and change the wettability of the shale surface. This increases the adsorption resistance of water molecules on the shale surface thereby inhibiting shale surface hydration. Third, SDY molecules can insert between the layers of bentonite sheets to bind the adjacent clay layers together, effectively inhibiting the permeable hydration of shale. This study provides an approach for addressing wellbore stability in deep wells with higher temperature.