Sequestration of carbon dioxide by steelmaking slag was studied in an atmospheric three-phase system containing industrial slag particles, water, and CO 2 gas. Batch-type reactors were used to measure the rate of aqueous alkaline leaching and slag particle carbonization independently. Four sizes of slag particles were tested for the Ca leaching rate in deionized water at a constant 7.5 pH in an argon atmosphere and for carbonate conversion with CO 2 bubbled through an aqueous suspension. Conversion data (fraction of Ca leached or converted to carbonate) were evaluated to determine the rate-limiting step based on the shrinking core model. For Ca leaching, the chemical reaction is the controlling mechanism during the initial period of time, which then switches to diffusion through the developed porous layer as the rate-limiting step. Carbonate conversion proceeded much slower than leaching conversion and was found to be limited by diffusion through the product calcium carbonate layer. The calculated value of diffusivity was found to be 5 · 10 -9 cm 2 /s, which decreased by an order of magnitude with increasing carbonization conversion as a result of changing density of the product layer. The experimental data fit the shrinking core model well after correction for the particle specific surface area.

Laboratory testing was conducted with a nutshell filter to determine the oil-removal performance on the basis of the flux rate, media type, media size, water salinity, and oil concentration. The goal was to determine the operating parameters that allowed <5 parts per million by volume (ppmv) of oil at the outlet, which is the normal operating point for this technology in producedwater treatment. Nutshell filters composed of black walnut or pecan granular media are an established produced water-treatment technology for tertiary oil removal. Guidelines for the size and operation of nutshell filters have evolved mainly by trial and error, with limited published operating data. This laboratory-research program tested a nutshell filter to determine the operating flux limits (flow rate per unit area) that provide suitable oil-removal performance. The separation-efficiency target was defined as 5 ppmv of oil in the outlet stream. The variables tested included medium type [black walnut shell (BWS) or pecan shell (PS)], medium size, filtration flux, water salinity, and oil concentration. The flux limit for common 12/20 media is 12.0 (gal/min)/ft 2 (or gpm/ft 2) for freshwater operation and 13.0 gpm/ft 2 for saline water. Decreasing the medium size to 20/30 mesh increased the allowable flux limit but at the expense of a substantial increase in the pressure drop. Oildroplet penetration into the filter bed proceeds by means of a near-plug-flow profile, with the top 18 in. of the bed providing 99% of the oil removal. Full breakthrough is a function of inlet concentration, with 20-30 hours of operation expected for a 48in.-deep bed.

Hydrous carbonate sequestration of carbon dioxide using steelmaking slag was studied using a METSIM process model to analyze experimental data and estimate the reactor operating results. Several scenarios of a two-stage system with water/slag contact in reactor 1 and leachate/carbon dioxide contact in reactor 2 were investigated. These scenarios included batch vs continuous processing and fresh water input vs water recirculation. The METSIM leaching and carbonation models were verified with results obtained from previous slag sequestration experiments. Fresh water additions to reactor 1 allowed the highest leaching efficiency and resulted in excellent carbonation in reactor 2, but a continuous system has a high water demand. Recirculation of the spent leachate minimizes the fresh water addition required, but inhibits the leaching process by producing a calcium carbonate product layer on the slag particles in reactor 1. Increasing the slag surface area, slag/solution ratio, or reactor residence time partially overcomes product layer ''blinding.'' Optimal residence times were defined for different process parameters and slag particle sizes.

A comprehensive system for the separation and handling of sand from produced fluids was designed and installed on a facility in the Gulf of Mexico. This system involves two multicone desander systems, one on the water outlet and one on the oil outlet of a lowpressure separator, to provide separation of sand from produced fluids. The separated solids are collected, dewatered, and transported to a unique, simple-solids handling system designed for complete fluid containment and safe handling. The focus of this paper is to present the design of the separation and handling system and to discuss the various challenges encountered during and after commissioning. The topics covered include desander operation (pressure drop and separation), slurry discharge from the desander, dewatering of slurry, recycling of fluids, and transport of the collected solids from platform to shore.

Facilities sand management is tasked with the goal of ensuring sustained hydrocarbon production when particulate solids (i.e. sand or proppant) are present in well fluids, while minimizing the impact of these produced solids on surface equipment. Particle size and total concentration of formation sand or proppant determines their net effect on production and the resulting operability of surface facilities. Conventional sand management control focuses on sand exclusion from the wellbore, either by production limits or completion design. Completions may adversely affect inflow due to skin buildup and both controls impede maximum hydrocarbon production. Alternatively, co-production of fluids and solids, with subsequent sand handling at surface facilities, is an inclusion paradigm that allows sustained hydrocarbon production. Produced solids are removed at the wellhead upstream of the choke using fit-for-purpose equipment. This methodology allows for increased or recovered hydrocarbon production, while their removal upstream of the choke protects facilities operations. A description of the design, performance, operation, and effect on production rate is provided for sand inclusive production through application examples in the Caspian Sea, Indonesia, and South China Sea. Specific reference is given towards wellhead desanding, which forms the greater part of this approach, and has expanded from the first field installation in 1995 in the UK to every major oilfield producing region. Implementation of dedicated facilities sand management technology has resulted in increased hydrocarbon production from sand producing wells, extension of well life on marginal fields, and re-start of shut in wells.

Sand production is a common challenge for processing facilities and well test equipment, as solids degrade the mechanical integrity and separation efficiency of surface equipment through erosion, settling, and plugging. Where exclusionary sand control methods fail or do not exist, inclusionary surface handling methods can be used to maintain or increase the total hydrocarbon production. The best approach is to remove sand at the wellhead, which protects all downstream flow lines and equipment. The multiphase (wellhead) desander was developed in the late 1990s as a unit operation to separate solids at wellhead conditions. This technology has been deployed in onshore and offshore production, well cleanup, and well testing operations. In addition to protecting downstream equipment, wellhead desanding enables the easier design and operation of solids-handling systems. Multiphase desanders were developed from solid-liquid cyclones used in the mining industry. Laboratory and pilot-plant tests conducted in 1994-1995 defined an initial hydraulic model, which was applicable in mixed-phase flow. The liquid-based model was paired with a dense-gas pneumatic cyclone model. The pressure drop and solids removal efficiency of the resulting multiphase model were evaluated at the Wytch Farm producing facility in Dorset, UK in 1995. This approach continues to be refined using field data, and the current mechanistic-empirical model has a high accuracy across the 0-100% gas void fraction range. The hydraulic and pneumatic models are discussed with respect to the pressure drop, solids removal, turndown, and slugging. Mechanical design improvements, including material selection, construction to API-6A code, and apex-flux balancing, have doubled the multiphase desander operating life while reducing the size and weight by 40%. Design improvements are discussed with respect to the system layout and proper operation. A comparison is made between single and multiple cone vessel designs with respect to the particle size, solids concentration, and fluid partitioning. Facilities Sand Management All oil and gas wells produce sand; therefore, all production facilities must be capable of managing sand in the flow streams. The most common methods of sand management attempt to exclude solid particles from the well flow using a production limit or completion string. When these approaches are not

fax 01-972-952-9435. AbstractAll oil and gas wells produce sand or solids in varying types and amounts. The size and concentration of natural solids (i.e. formation sand) and artificial solids (i.e. workover debris) determine their net effect on production equipment and the resulting management of hydrocarbon production. Conventional exclusion methodology prevents solids from entering the wellbore but may adversely affect inflow production due to skin buildup. Inclusion methodology allows the solids to be produced with well fluids for surface separation and handling. A comparison of the performance, operability, cost impact, and effect on production rate is made for both methods through application examples. The goal is to show that the increased production resulting from allowing solids to be produced in some high sand rate wells allows more sustainable hydrocarbon production with a cost benefit compared to downhole exclusion for certain producing regions.

Nutshell filters composed of black walnut or pecan granular media are an established produced water treatment technology for tertiary oil removal. Guidelines for the size and operation of nutshell filters have evolved mainly by trial and error, with limited published operating data. This laboratory research program tested a nutshell filter to determine the operating flux limits (flow rate per unit area) that provide suitable oil removal performance. The separation efficiency target was defined as 5 ppmv oil in the outlet stream. The variables tested included medium type (black walnut shell or pecan shell), medium size, filtration flux, water salinity, and oil concentration. The flux limit for common 12/20 media is 12.0 gpm/ft2 for fresh water operation and 13.0 gpm/ft2 for saline water. Decreasing the medium size to 20/30 mesh increased the allowable flux limit but at the expense of a substantial increase in the pressure drop. Oil droplet penetration into the filter bed proceeds via a near plug-flow profile, with the top 18 inches of the bed providing 99% of the oil removal. Full breakthrough is a function of inlet oil concentration, with 20-30 hours of operation expected for a 48-inch-deep bed. Testing for removal of fine sand particles showed a average 5 µm separation size for 12/20 media at 13.5 gpm/ft2 flux.