Openhole Gravel-Pack Case Histories in Wells Drilled With a Synthetic Mud: Successful Implementation of an Alternative Method in Oyo Field, Nigeria

Abstract

Openhole gravel packing is a popular completion technique 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-base fluids before running screens and subsequent gravel packing. Although successful in some cases, this technique has been problematic in reactive shale environments, due to problems in screen installation to target depth, resulting from shale swelling and/or collapse. Such problems led operators to a two-trip approach, where a predrilled liner is installed in synthetic-base mud (SBM), displacements performed to water-base fluids and the screens are run in solids-free water-base fluids environment, followed by gravel packing. In recent years, another approach was introduced, in which the displacements to water-base fluids are performed after the screens are installed in conditioned mud and the packer is set, followed by gravel packing with a water-base 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 openhole was displaced to a solids-free SBM and cased hole to completion brine, and gravel packing was performed using a water-base carrier fluid. This approach provides a cost-effective alternative to displacement of the entire wellbore to solids-free SBM as well as eliminating the risk of screen plugging, and was successfully implemented 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, along with a discussion of a continuous circulation device successfully used during drilling.