On the Hydraulics of Inverted Flow Path Gravel Pack Operations

Abstract

The hydraulics of inverted flow path gravel pack operations is studied utilizing a transient flow simulator. Inverted flow path or more simply, inverted gravel packs can be employed in horizontal or fishhook wells wherein the well/screen annulus is partially packed first in the toe-to-heel direction (alpha wave) followed by packing in the heel-to-toe direction (beta wave) to complete the pack. Until the present time, conventional gravel packs in which the well/screen annulus is partially packed in the heel-to-toe direction (alpha wave) prior to completing the pack in the toe-to-heel direction (beta wave) have primarily been utilized for sand control in horizontal or deviated wells. In addition, alternate flow path technology (e.g. shunt tubes) has also been utilized along with conventional gravel packs. However, in the case of fishhook wells, conventional gravel packs may need to surmount an uphill slope during the alpha wave and can cause operational difficulties such as premature bridging and fracturing the formation at the heel during the beta wave. These operational difficulties may be overcome by employing inverted gravel packs wherein slurry is delivered into the well/screen annulus at the toe and the alpha wave is performed along the downhill slope thereby reducing the risk of formation fracturing at the heel and premature bridging in the annulus. In this paper, hydraulics of inverted flow path gravel packs is investigated utilizing a transient flow simulator. A field example is considered and a comparative study is performed on the hydraulics of inverted and conventional gravel pack operations. Results from the field example simulations are discussed from both steady-state and transient view points. Steady-state results include pressure profiles with measured depth for select slurry front locations in the well/screen annulus. Transient results are presented as variations of pump, gravel pack packer (heel), bottomhole (toe), and maximum well/screen annulus pressure with elapsed time. These simulations in conjunction with a mathematical analysis provide some insight into the inverted gravel pack hydraulics and associated pressures in comparison with conventional gravel packs. Results show that inverted gravel packs significantly reduce the maximum pressures experienced in the well/screen annulus compared to conventional gravel packing.