Over 1,000 horizontal and curved radiais have been placed in unconsolidated, sandstone and limestone formations in the U.S. and Canada with the Ultrashort Radius Radial System. All radiais are drilled with high pressure, water-based fluids (69 MPa (10,000 psi)) with appropriate additives. These radiais move from the vertical to the horizontal around a 30 cm (1 ft) radius of curvature. Multiple radiais (up to 20 per layer) and multiple layers (up to 5 layers) have been successfully drilled. Most radiais have been positionally surveyed. Horizontal completions including open hole, Flexible Sand Barrier (flexible permeable casing), and gravel packing have been employed. Some radiais have been placed using Control While Drilling which incorporates real-time downhole indication of drillhead trajectory coupled with real-time trajectory control supplied by small thrust jets which move the drillhead up or down so as to follow a desired trajectory.
Field conditions of water coning, natural fracturing, hard-soft inclusions, shale partitions, faulting, and other common reservoir heterogeneities have been encountered. Applications have been made in both heavy and light oils. A typical successful controlled injection/production (huff and puff) application of the system with production results is described in detail.