The invention discloses an environment-friendly, low-damage and clay-free
deep water constant-
rheology drilling fluid comprising the following components in percentage by
mass: 0.35-0.5% of
alkalinity regulator, 0.4-0.5% of tackifying agent, 7-10% of inhibitor, 2.1-2.5% of filtrate
reducer, 3-5% of lubricating agent, 0.3-0.5% of mud cake quality modifying agent, 0-0.8% of
viscosity reducer, 0-61.2% of weighting agent and the balance of
seawater. The environment-friendly, low-damage and clay-free
deep water constant-
rheology drilling fluid is free of biotoxicity, easy to biologically degrade and environment friendly; the EC50 value of the
drilling fluid is larger than 120000mg / L, the
rock core permeability
recovery rate is 87.37%, a polluted segment is shorter than 0.5cm, the damage of foreign fluid to a
hydrocarbon reservoir can be reduced, and the
ocean environment can be effectively protected; the drilling fluid disclosed by the invention can
resist to the temperature of 120 DEG C, has the controllable density of 2.0g / cm<3> and constant dynamic shearing force at different test temperatures after being subjected to hot rolling for 16h, and is favorable in
thixotropy, relatively strong in shearing dilutability, easy to form a flat plate flow and strong in rock
carrying capacity. By using the environment-friendly, low-damage and clay-free
deep water constant-
rheology drilling fluid, the in-well pressure kick, the ECD (Equivalent Circulating Density) value and the borehole
slurry leakage can be effectively reduced, the
slurry loss of a vibrating screen is avoided, the borehole cleanness is improved, and the non-production
operation time is saved.