The Effects of Non-Darcy Flow in Propped Hydraulic Fractures

Abstract

Abstract Hydraulic fracturing is being applied to progressively higher permeability formations. In many cases, productivity improvements are controlled by the achievable fracture conductivities. An analysis of the effects of non-Darcy flow in high rate oil and gas wells shows that in gas wells, fracture conductivities are dominated by non-Darcy effects and that effective conductivities are non-linearly dependent on proppant coverage. Laboratory tests to investigate non-Darcy flow effects in proppant packs have been performed at rates much closer to field conditions than hitherto reported; both single and two-phase flows are considered. Dry gas tests have demonstrated that there is a change in pressure loss behaviour and flow regime at high rates. Three types of test involving gas and water flows have been performed. First the effects water-saturated gas flowing in a proppant pack at residual water saturation were compared with results on the same pack with dry gas. Two series of experiments were then performed to examine the effects of mobile water in the gas stream. Pressure losses are shown to be very sensitive to the water rates, and the field implications are examined. Finally field data from tests performed on high rate, hydraulically fractured, gas wells are examined. Perceived fracture conductivities are related to estimated proppant coverage, and it is shown that non-uniform vertical distributions of proppant may have a large impact on the overall fracture flow capacity.