X-ray photoelectron spectroscopy (XPS) was applied to investigate Mn(II) removal by MnO(x)(s)-coated media under experimental conditions similar to the engineered environment of drinking water treatment plants in the absence and presence of chlorine. Macroscopic and spectroscopic results suggest that Mn(II) removal at pH 6.3 and pH 7.2 in the absence of chlorine was mainly due to adsorption onto the MnO(x)(s) surface coating, while removal in the presence of chlorine was due to a combination of initial surface adsorption followed by subsequent surface-catalyzed oxidation. However, Mn(III) was identified by XPS analyses of the Mn 3p photoline for experiments performed in the absence of chlorine at pH 6.3 and pH 7.2, suggesting that surface-catalyzed Mn oxidation also occurred at these conditions. Results obtained at pH 8.2 at 8 and 0.5 mg·L(-1) dissolved oxygen in the absence of chlorine suggest that Mn(II) removal was mainly due to initial adsorption followed by surface-catalyzed oxidation. XPS analyses suggest that Mn(IV) was the predominant species in experiments operated in the presence of chlorine. This study confirms that the use of chlorine combined with the catalytic action of MnO(x)(s) oxides is effective for Mn(II) removal from drinking water filtration systems.

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The manganese oxide (MnOx(s)) coatings often found on water treatment filtration media are known to effectively remove dissolved manganese from water, but little is known about the chemistry and the formation of these MnOx(s) coatings. This study evaluated the role of particulate aluminum (Al) species (specifically Al(OH)3(am)) as a source for aluminum found in these media coatings. Bench‐scale experiments and surface analysis techniques evaluated the aluminum and manganese content of the media coatings formed under varying conditions. Particulate aluminum species were shown to be a significant source of aluminum in the MnOx(s)‐based coatings on filter media. Likewise, aluminum incorporation into the media coating did not take place without soluble manganese and free chlorine concurrently being applied to the filter media. Analysis of the MnOx(s) coating by electron microscopy showed a heterogeneous surface composed of a mix of weakly crystalline manganese oxides existing alongside amorphous Al(OH)3(am) species.

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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...