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A weak, laminar shear flow of a monodisperse suspension of high-Reynolds-number, low-Weber-number bubbles is studied in a novel experimental configuration. Nitrogen bubbles are formed through an array of small capillaries at the base of a tall channel with a small inclination from the vertical. The bubbles generate a unidirectional shear flow, in which the denser suspension near the bottom wall falls and the lighter suspension near the top wall rises. Profiles of the bubble and liquid velocities and the bubble volume fraction are obtained using hot-film and dual impedance probes. To our knowledge, measurements of the laminar shear properties of a nearly homogeneous bubble suspension have not previously been reported.A steady shear flow is observed in which the bubble velocity variation across the channel is typically less than 20% of the mean bubble velocity. The velocity and volume fraction gradients increase with channel inclination and exhibit little or no dependence on the mean gas volume fraction. To explain the magnitude of the volume fraction gradients, it is necessary to consider the effects of both the lift force and the effective bubble-phase diffusivity in balancing the segregating tendency of the cross-channel component of the buoyancy force. The bubble velocity gradient can be understood in terms of a balance of the component of the buoyancy force parallel to the channel walls and an effective viscosity associated with the Reynolds stresses produced by bubble-induced liquid velocity fluctuations. Theories for bubbles rising with potential-flow hydrodynamic interactions predict an instability of the homogeneous state due to a negative Maxwell pressure. However, the hydrodynamic diffusivity inferred from our experiments is large enough to mitigate the clustering effects of the Maxwell pressure. Consistent with this, a vigorous instability of the homogeneous state of the bubble suspension is only observed at volume fractions larger than 5%–20% with the critical volume fraction depending on the angle of inclination.

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Hydrogen sulfide (H2S) is found in many shale gas fields. It is important to remove the H2S to allow for safe transport of the produced gas and to reduce corrosion concerns. The H2S concentration present in the gas is typically low enough that it becomes uneconomical to utilize a regenerative facility such as an amine plant. For this reason, liquid H2S scavengers are the most common mitigation strategy, with nitrogen-based triazines being the most commonly utilized scavenging chemistry. Hydrogen sulfide scavengers can be introduced by direct injection2 into mixed production or separated wet gas pipelines. They can also be reacted with H2S in scavenger flooded contact towers. Applications utilizing towers consume less H2S scavenger; however, the use of contact towers introduces additional capital costs in the operation. Often when high pH, triazine-based H2S scavengers are used, calcium carbonate scale deposition can occur because of neutral pH brine, requiring the facility to be shut in and treated with mineral acids. The reaction product of triazine with H2S can be difficult to dispose of, which increases facility operating costs (e.g. separate disposal tanks and dedicated disposal wells for spent scavenger). A novel, fast-acting, non-triazine based H2S scavenger has been developed. This new H2S scavenger reacts quicker and has better efficiency than other non-nitrogenous based scavengers (e.g. glyoxal). The neutral pH of the new product eliminates the concern for calcium carbonate deposition that is often experienced with triazine-based scavengers. The new scavenger has been tested for thermal stability and compatibility with other production chemicals. The product has the ability to partition in oil and water phases, making it a more versatile scavenger. Finally, the new product has a better environmental profile than other commonly used H2S scavenger chemistries. A field trial was conducted using the new non-triazine H2S scavenger. The trial included direct injection into mixed production and separated wet gas lines. Innovative engineering solutions were devised to apply the new H2S scavenger. The combination of the novel application methodology, with the new H2S scavenger chemistry, resulted in a more cost-effective means of treating sour shale gas than is currently achieved with conventional triazine-based H2S scavengers utilizing contact tower applications.