Abstract: A star-shaped polyacrylamide copolymer and a preparation method thereof are provided, as well as a drilling fluid containing the star-shaped polyacrylamide copolymer. Only the star-shaped polyacrylamide copolymer is added into the drilling fluid; under a high-temperature environment, the filtration volume of the drilling fluid can be reduced, the high-temperature rheological property of the drilling fluid is improved, and the pressure loss of a circulation system of the drilling fluid is reduced.

Abstract: A star-shaped polyacrylamide copolymer and a preparation method thereof are provided, as well as a drilling fluid containing the star-shaped polyacrylamide copolymer. Only the star-shaped polyacrylamide copolymer is added into the drilling fluid; under a high-temperature environment, the filtration volume of the drilling fluid can be reduced, the high-temperature rheological property of the drilling fluid is improved, and the pressure loss of a circulation system of the drilling fluid is reduced.

Abstract: An electropositive and water-based production well treating fluid system exhibits electropositivity by using a cationic viscosifier meanwhile matched with a cationic fluid loss additive and, optionally, contains a mud-building agent, an electrical stabilizing agent, a colloid-stabilizing agent, lubricant, an oil layer protective agent and/or a weighting agent. The electropositive production well treating fluid can beffer solve the contradiction of technical requirements between “treating fluid stability” and “bore hole stability”, and features a strong ability to inhibit the dispersion of clay, a good effect of protecting oil-gas reservoirs, fast drilling speeds, regular shape of bore holes and good resistance to salt.

Abstract: The present invention provides an electropositive and water-based production well treating fluid system. The production well treating fluid system can be made to exhibit electropositivity by using a cationic viscosifier meanwhile matched with a cationic fluid loss additive and optionally matched with a mud-building agent, electrical stabilizing agent, colloid-stabilizing agent, lubricant, oil layer protective agent and/or weighting agent. Such kind of electropositive production well treating fluid can solve better the contradiction between “treating fluid stability” and “bore hole stability”, and has features in strong ability of inhibiting the dispersion of clay, good effect of protecting oil-gas reservoir, fast drilling speed, regular shape of bore hole and good resistance to salt. The present invention relates further to a method of preparing said production well treating fluid system and use of the drilling fluid and well completion fluid in petroleum drilling and well completion.