Abstract: A filtrate reducer for temperature-resistant calcium-resistant water-based drilling fluid used in oil and gas reservoir protection, a drilling fluid, and uses of the filtrate reducer and the drilling fluid are described. The filtrate reducer contains structural units represented by formulas (1), (2), and (3) herein. The water-based drilling fluid contains the filtrate reducer, and exhibits good inhibitive, rheological, filtrate reducing, and reservoir protection performance when it is applied in the drilling process in a high-temperature high-calcium deep salt-gypsum formation.

Abstract: The present invention relates to the technical field of petroleum and natural gas well drilling, and discloses a filtrate reducer for temperature-resistant calcium-resistant water-based drilling fluid used in oil and gas reservoir protection, a drilling fluid, and uses of the filtrate reducer and the drilling fluid. The filtrate reducer for temperature-resistant calcium-resistant water-based drilling fluid used in oil and gas reservoir protection contains structural units represented by formula (1), structural units represented by formula (2), and structural units represented by formula (3), wherein the mass ratio of the structural units represented by formula (1) to the structural units represented by formula (2) to the structural units represented by formula (3) is (0.1-0.2):1:(0.05-0.1), and the number-average molecular weight of the filtrate reducer is 10,000-100,000.