Ultra-Low-Density Drilling Fluids for Low-Pressure Coefficient Formations: Synergistic Effects of Surfactants and Hollow Glass Microspheres

With the increase in drilling fluid density requirements low-pressure coefficient formations, traditional hollow bead fluids and foam each have different degrees of deficiencies. Through extensive indoor experiments, an amphoteric surfactant (cocoamidopropyl betaine) with better foaming performance was selected to formulate ultra-low-density that combines a agent glass microbeads reduce fluid, following specific formulation: 3% bentonite slurry + 0.3% xanthan gum 0.5% carboxymethyl cellulose starch 2% lignite resin blocking 4% microspheres nano agent. The system evaluated, results showed that: did not change much before after aging at 80 °C relatively stable; filter loss amount (tested by API) reached 4.6 mL, which meets for fluid; it can bear pressure 12 MPa under 60–90-mesh sand bed has sealing capability than microbead fluid.