Abstract: A random copolymer, a preparation method of the random copolymer, a drilling fluid containing the random copolymer. The random copolymer contains structural unit (A) represented by formula (1), structural unit (B) represented by formula (2), structural unit (C) represented by formula (3), and structural unit (D) represented by formula (4) or (5): wherein X is halogen. When the random copolymer is used as a filter loss reducer in a high-calcium drilling fluid, the filter loss of the high-calcium drilling fluid can be reduced.

Abstract: A maleamic acid monomer, and a preparation method and a use of the maleamic acid monomer. The structural formula of the monomer is as follows: formula (1), wherein, R is selected from The maleamic acid monomer provided in the present invention may be used as a comonomer to prepare temperature-tolerant and calcium salt-tolerant polymers.

Abstract: A random copolymer, a preparation method of the random copolymer, a drilling fluid containing the random copolymer. The random copolymer contains structural unit (A) represented by formula (1), structural unit (B) represented by formula (2), structural unit (C) represented by formula (3), and structural unit (D) represented by formula (4) or (5): wherein X is halogen. When the random copolymer is used as a filter loss reducer in a high-calcium drilling fluid, the filter loss of the high-calcium drilling fluid can be reduced.

Abstract: A composition and use thereof are disclosed herein. The composition comprises at least two selected from the group of amphiphilic block copolymer, polyurethane and acidic ionic compound. Also an oil-based drilling fluid comprising the composition and a method improving shearing force of oil-based drilling fluid are disclosed. The composition disclosed herewith can raise the shearing force of oil-based drilling fluid.

Abstract: A composition and use thereof are disclosed herein. The composition comprises at least two selected from the group of amphiphilic block copolymer, polyurethane and acidic ionic compound. Also an oil-based drilling fluid comprising the composition and a method improving shearing force of oil-based drilling fluid are disclosed. The composition disclosed herewith can raise the shearing force of oil-based drilling fluid.

Abstract: The present invention provides a filtration control agent and a drilling fluid containing the same. The filtration control agent comprises the product obtained from the reaction of water, lignite, aldehyde and sulfonate polymer at 180-220° C. and the units containing sulfonate groups in the molecular chains of sulfonate polymer are at least 30 wt %. The filtration control agent provided by the present invention features a good filtration loss reduction effect and a low viscosity effect and can improve the rheological behavior of the drilling fluid, thereby meeting the requirements of the drilling of deep wells, ultra-deep wells and ultra high pressure formations.

Abstract: The present invention provides a modified starch, preparation method and use of the same, also provides a drilling fluid comprising the modified starch which contains bi-substituted starch structural units and tri-substituted starch structural units, wherein, the tri-substituted starch structural units are represented by the following formula (1), the bi-substituted starch structural units are the structural units represented by the following formula (2) and/or the structural units represented by the following formula (3), and the total content of the bi-substituted starch structural units and tri-substituted starch structural units accounts for 20 wt % or more of the modified starch, preferably 20-30 wt %, the weight-average molecular weight of the etherified starch is 50,000-600,000, preferably 80,000-580,000, wherein, R1, R2, and R3 are C1-C5 alkylene respectively, and M1, M2, and M3 are H, alkali metal element, or alkaline earth metal element respectively.