Amerada study in Western Foothills documents evolution of fracture designs. In 1960’s – 20 tonnes and concentrations up to 600 kg/m3. In 1990 – acidizing (marginal results + scaling). In 1992 – Intense re-fracturing program, with concentrations increased 3.3 fold; tonnage was increased 100%. 17 refrac treatments performed (2 on gas wells). All wells show increased production, ranging from 62% to 1043%. Average three month production rates up 2.5 fold. Total incremental oil production estimated at 165,210 m3. NPV of project to date is $3.3 million.
Stimulation of Amerada's Cardium formation in the Western Foothills has produced mixed results. Stimulation techniques have been performed as early as the 1960's. Before 1990, hydraulic fracturing treatments were the primary stimulation technique with treatment sizes up to 20 tonnes and maximum proppant concentrations of only 600 kg/m3. Due to the inconsistent results, an acidizing program was incorporated in 1990. This program produced marginal results due to an increase in formation scaling tendencies. An intense re-fracturing program was initiated in 1992 with intentions of increasing success through careful candidate selection and job-design.
The re-fracturing program was initialized with mini-frac techniques to enhance geological and reservoir data. A fluid capable of transporting high concentrations of proppants through the highly tortuous near wellbore region was required. With the evolution of the hybrid fracturing fluid. total fluid volumes have been reduced, therefore minimizing proppant convection and increasing fracture conductivity, and reducing costs.
The new fluid has allowed the proppant concentrations to be increased 3.3 fold, and proppant tonnage by 100 % while decreasing the frac fluid to proppant ratio from 4.35 m3/tonne average to 1.35 m3/tonne. The three month average oil production rate has increased by 2.5 times.
Author(s): D. J. McMillan, Nowsco Well Service Ltd.; R. D. Suffron, Amerada Hess Canada Ltd.
Paper Number: CIM 95-44