Experimental evaluation demonstrates that size-matched bridging materials limit drilling mud invasion to under one inch in permeable rock, suggesting preserved well productivity.
Key Points
To establish design criteria for drilling muds using solid bridging additives to minimize particle invasion and permeability damage in reservoir rocks.
Determined mud solids size distributions using the Coulter counter method and estimated rock pore sizes from permeability and capillary pressure data.
Conducted radial-flow tests with a laboratory mud on 4- to 6-darcy unconsolidated sand and linear flow tests with field mud on 5- and 50-md dolomite cores.
Mud formulated with bridging additive median sizes at least one-third of the formation pore size and at concentrations of at least 5% by solids volume restricted invasion to less than 1 inch.
Observed impairment depths remained within typical perforation penetration limits without significantly altering injectivity or productivity, though backflushing failed to reverse invasion damage.