Stimulation Fracture Height Control Above Water or Depleted Zones

Abstract

Abstract Many potentially productive zones located a few meters (feet) above a water or pressure-depleted interval are not fracture-stimulated, or are eliminated from further investigation rather than risk inter-zone communication. In either case, production fails to be optimized and often recoverable reserves are lost. Several techniques for controlling formation fracture height growth have been successfully field-tested. The fracturing fluid used was either water- or oil-based with a low viscosity of 20 to 50 cp. A general program, utilizing a timed sequence of rate and proppant concentration control, is preceded by application of fracture height-controlling material in the pad. Approximately 5 tonne (11,000 lb) of proppant were consistently placed with total fracture height growth traced to less than 15 m (50 ft). Post-stimulation well testing indicated fracture lengths to 90 m (300 ft) in reservoirs having permeabilities as low as 0.1 md. Fracture modeling using a numerical simulator prior to actual field stimulation has proven to be instrumental in designing an optimal fracture program. This unified procedure prevents or minimizes fracture height growth, from initial breakdown of the formation to the flow period after pumping. Well stimulation is performed through tubing to reduce fluid volumes. Pumping rates ranged from 0.5 to 1.5 m3/min (3.1 to 9.4 bbl/min). To date, ten treatments have been successfully placed and there is no evidence to suggest that fracture heights were greater than those predicted by computer simulation.