Openhole Gravel-Pack Case Histories Using Alternative Fluid Displacement for Synthetic-Based Mud

Abstract

Openhole gravel packing is one of the popular completion techniques in challenging, high-transmissibility reservoirs. Many of such wells are drilled with synthetic fluids and completed with either a single-or a two-trip technique.In single-trip approaches, the entire wellbore is displaced to water-based fluids before running screens and subsequent gravel packing. Although successful in some cases, this technique has been problematic in reactive-shale environments because of problems in screen installation to target depth, resulting from shale swelling and/or collapse. Such problems led operators to a twotrip approach in which a predrilled liner is installed in syntheticbased mud (SBM), displacements are performed to water-based fluids, and the screens are run in a solids-free (SF) water-basedfluids environment, followed by gravel packing. In recent years, another approach was introduced, in which the displacements to water-based fluids are performed after the screens are installed in conditioned mud and the packer is set, followed by gravel packing with a water-based fluid. Although this approach eliminates the difficulties associated with screen installation as well as allowing a single-trip completion (no predrilled liner), it cannot be used in cases where conditioning is impractical.In this paper, we present case histories where screens were installed after the open hole was displaced to a solids-free SBM and the cased hole was displaced to completion brine, and gravel packing was performed using a water-based carrier fluid. This approach provides a cost-effective alternative to displacement of the entire wellbore to SF-SBM as well as eliminating the risk of screen plugging, and it was implemented successfully on two oil producers in Oyo field. Details of design, execution, and evaluation for drilling and completion stages, as well as well productivity measures, are provided. Review of the Practices to DateMany of the deepwater developments in West Africa use SBMs for both upper hole and reservoir drilling, and almost all of them require some form of sand control, openhole gravel packing being one of the widely used techniques. Gravel packing in SBM environments evolved substantially over the years, with a variety of options that can be categorized on the basis of the type of carrier fluid used for gravel packing [note that the terms SBM and oil-based mud (OBM) are used interchangeably in the context of this paper].Oil-Based Carrier Fluid. In this approach, the screens are necessarily installed with oil-based fl uids in the entire wellbore, where the wellbore fl uids can be any combination of (a) conditioned SBM, (b) fresh SBM (no cuttings), and (c) SF-SBM or oil-based carrier fl uid. The conditioned-SBM approach requires that the mud be passed through shaker-screens of suffi ciently small openings to prevent plugging of sand-control screens during installation and subsequent operations. As such, the type of screens used in the completion (wire-wrap or premium/metal-mesh) and the size of screen openings, and t...

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