This paper presents results of an extensive laboratory and field program to optimize the fracturing fluid system used in the ARCO-operated Eastern Operating Area of the Prudhoe Bay Unit on the north slope of Alaska. This study focuses on the fracturing fluid rheology, fluid loss additives and retained proppant conductivity for this high permeability fracturing application. Results of 60 static fluid loss tests performed on filter paper led to optimization of degradable starch loadings and identification of 5% diesel as an effective fluid loss additive. Subsequent dynamic fluid loss tests on Prudhoe core discounted benefit of the diesel, but proppant conductivity testing showed the diesel did improve proppant pack clean-up. Results of mini-fracs performed showed diesel provided identical performance to the significantly more costly degradable starch additive. Laboratory tests of fluid rheology found that orders-of-magnitude increases in viscosity could be obtained by increasing the pH of the delayed-borate crosslinked guar systems used for the 200°F BHT. Despite recent changes in strategy due to smaller treatment sizes (as described by Martins et al1 ), the results of these laboratory tests have been used to dramatically lower fluid loss additive costs and improve fluid system performance in the high permeability Prudhoe fracturing program.

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