William G. F. Ford

Enhanced Water Recovery Improves Stimulation Results

The effects of capillary pressure, wettability, and relative permeability in controlling load water recovery following hydraulic-fracturing treatments have been examined. Laboratory studies have indicated that the alteration of wettability to control capillary pressure and/or relative permeability can promote a rapid, thorough cleanup of injected water. Field applications of these concepts have resulted in enhanced load water recoveries and higher production because of longer effective fracture lengths and/or higher effective fracture conductivities after treatment cleanup.

Influence of Downhole Conditions on the Leakoff Properties of Fracturing Fluids

The leakoff velocity of complexed fracturing fluids is highly dependent on environmental conditions. Previous work has shown that leakoff increases as the shear rate increases. This work examines the combined effects of shear rate, pressure differential, temperature, and time on the leakoff profile in complexed gels. Results have shown that C/sub W/ under simulated reservoir conditions is not proportional to P to the 1/2 and t to the 1/2 as proposed by classical theory. C/sub W/ was found to be proportional to P to the 1/6. Leakoff velocity follows a t to the n relationship, where n = 0.5 to 1.0, depending on shear rate, pressure differential, and time at shear. An equation is represented whereby the leakoff velocity at each increment of the treatment can be calculated based on changing environmental conditions.

Foamed Acid An Effective Stimulation Fluid

Dynamic laboratory testing of foamed acid on limestone cores has established the effectiveness of foamed acid as a stimulation fluid. The effects of foam quality, stability, and chemical compatibility on fluid loss and fracture flow capacity were investigated. Recommendations are presented for deriving maximum benefits from a foamed acid treatment. Field results are presented that show the effectiveness of foamed acid in the stimulation of both oil and gas wells. 23 refs.