Lost Circulation Remains R & D Focus

摘要

Lost circulation remains a fundamental issue in many drilling environments. Preventing lost circulation with oil-based drilling fluids was the focus of the Drilling Engineering Association 13, a joint industry project conducted in the mid-1980s. The theory and experimental results resulting from DEA 13 gave insights into the fundamental differences between oil-based and water-based fluids that resulted in lost circulation. They included: 1. High-density water-based mud exhibited higher fracture extension pressures than the oil-based mud systems. 2. There was no significant correlation between mud types and fracture initiation pressures in intact bore holes. 3. Fracture healing was more significant in water-based, mud-induced fractures than those created with oil-based mud. 4. The most effective lost circulation material treatment for oil-based, mud-induced fractures in permeable rocks is a high fluid loss water-based mud pill. 5. The major difference between high-density oil- and water-based muds with respect to lost circulation inducement lies in their reopening and propagation pres- sures (both pressures are lower for an oil-based fluid than a water-based fluid).