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filtration

PPT Slotted Disc

Purpose

Evaluate the bridging and sealing performance of a drilling fluid or treatment across a slotted disc that simulates a natural fracture or vug. Used to size bridging materials for fracture-width-based lost-circulation control in open-hole completions and reservoir sections.

Equipment

  • PPT cell with slotted disc holder
  • Slotted stainless-steel disc (specified slot width, e.g. 500 µm, 1 mm, or 2 mm)
  • Nitrogen pressure source
  • Graduated collector tube, 10 mL or 25 mL
  • Timer
  • Back-pressure regulator (optional)

Procedure

  1. Select the slotted disc with the target slot width; inspect for cleanliness and integrity.
  2. Assemble the PPT cell with the slotted disc in place; seat O-rings and end caps securely.
  3. Fill the cell with well-mixed mud sample (including bridging agents) from the top inlet.
  4. Apply the specified differential pressure.
  5. Start the timer simultaneously with pressure application.
  6. Collect and record filtrate at 1, 2, 5, 10, 15, and 30 minutes.
  7. After the test, disassemble the cell and inspect the disc for bridging plug quality.

Notes

  • Report filtrate volumes at each time interval and total at 30 minutes.
  • Record slot width, applied pressure, and whether a competent bridge formed.
  • The ideal result is a tight bridge formed early with negligible subsequent filtrate.
  • Slot width should be matched to the estimated fracture aperture for the target formation.
  • Clean the disc thoroughly after each test; residual particles affect subsequent results.