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Following the reduction of system pressure through depletion compression more than 150 deep gas wells started struggling from halite deposition. Halite deposition in the completion restricted or blocked the production from the lower reservoir in these wells and reduced the total gas production of the field by about 40%. Meanwhile, many of the wells with halite deposition issue were also suffering from liquid loading and velocity strings were isntalled in them as the primary means of gas well deliquification. Many of these wells with velocity string showed no further halite deposition due to increase of the bottom hole pressure and reduction of the draw-down. Consequently, frequent freshwater bull heading or clean out with coiled tubing were no longer needed. This observation triggered the idea to create synergy between gas well deliquification and halite management through installation of velocty string. This synergy does not exist in every case, and this paper elaborates on identifying where it exists.

The use of reactive transport modeling (RTM) is increasing in the oil and gas industry for assessing the geochemical impact (e.g. scaling and souring) of various activities, such as waterflooding for improved oil recovery (IOR) and CO2 storage. RTM is a technique that integrates fluid flow, transport of heat and solutes, and geochemical reactions. It can be used to model fluid compositional changes as well as rock mineralogical changes, caused by geochemical reactions, under flowing conditions. We use our in-house reservoir simulator (MoReS), coupled to geochemical software (PHREEQC), to carry out RTM. Simulations are based on the mixed solvent electrolyte (MSE) model from OLI Studio, a standard tool used by production chemists, enabling accurate computation of aqueous chemical reactions and partitioning of components between solid, fluid and gas phases. Over the last few years we have used RTM to make scale predictions for several waterflooding projects around the globe. In this paper we will show results from these field cases and highlight the most important findings. In brief, these are: Enabling mineral precipitation reactions in flow calculations improves the match between measured and simulated production water (PW) chemistry.Full 3D reservoir models capture different flow paths arriving/mixing near production wells, enabling an improved match between historical and simulated PW chemistry. Simplified (1D/2D) models are sufficient for predicting the magnitude of scale deposition and screening scale prediction uncertainties when little is known about reservoir connectivity (e.g. new developments).Inclusion of clay mineral cation exchange reactions significantly modifies the evolution of the injected water composition during migration through the reservoir. As a result, this impacts the reservoir deposition of scaling minerals (e.g. barite) and the scaling potential of production wells. Characterization of cation exchange properties of clay minerals in reservoirs is therefore recommended. The developed workflow, based on learnings from various projects, is now used to forecast scaling risks in new projects and supports ongoing projects in mitigating risks (e.g. selection/timing scale squeezes).

In commercial slabstock foaming, liquid CO2 technology is increasingly applied to replace previously used liquid auxiliary blowing agents like CFCs and methylene chloride. Knowledge of physical properties of mixtures which are used in liquidCO2 foaming may contribute to the further development of the liquid CO2 technology. Equations have been determined which do predict, for specific operational conditions and formulations, the pressures which are required in commercial foam operation to keep theCO2 dissolved both in the polyol/CO2 and in the foaming mixture/CO2 solutions. The evident dependence on temperature ofCO2 solubility, established for both polyol and foaming mixtures, strongly supports tight temperature control of the feedstocks in slabstock liquid CO2 foaming. The solubility of CO2 in polyol was found to increase with the EO content of the polyol where the effect of molecular weight was found to be negligible. It was established that small amounts of water and surfactant lower the CO2 solubility, and it is predicted that the commonly used levels of TDI do the same. Based on this information, it is advisable to conduct the mixing of TDI and auxiliary components at pressures a fraction higher than the saturation pressure of the liquid CO2 polyol mixture. A significant decrease of both viscosity and surface tension is quantified for polyol and model foaming systems at increasing liquidCO2 concentration. These decreases may explain why very small cell sizes can be obtained with liquid CO2 foaming, as the nucleation process takes place at high liquid CO2 concentration. The rise in viscosity upon evaporation ofCO2 into the froth may explain the relative stability of the unreacted froth. A cooling capacity of about 1°C per part of CO2 per hundred parts of polyol is determined from two independent experiments. However, for safety reasons, it is advisable to keep the current assumption of 0°C per part of CO2 per hundred parts of polyol in commercial foaming until a further study on the temperature evolution of liquidCO2 blown foaming under practical conditions is conducted.

Thin films (80–100 nm) of zinc titanate with Zn/Ti ratios between 0.5 and 2.7 were prepared on 2 ′′ Si(100) wafers via the metallo-organic decomposition (MOD) technique. Their morphology, composition, and structure were extensively characterized by high resolution scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy (XPS), Rutherford backscattering spectroscopy, energy dispersive X-ray analysis, secondary ion mass spectrometry (SIMS), X-ray diffraction (XRD), and glancing incidence XRD (GIXRD). The catalytic performance of these zinc titanate thin films in isobutane dehydrogenation was studied in a newly designed and built wafer reactor in the pulse mode. The zinc titanate films prepared via MOD consisted of irregularly shaped grains. The Zn/Ti ratio of the film surface as measured with XPS was slightly higher than that of the bulk, indicating some zinc enrichment on the surface. However, the overall composition through the film was reasonably homogeneous as revealed by a SIMS depth profiling study. GIXRD showed the existence of the same zinc titanate phases at all film depths, again indicating a homogeneous film. The zinc titanate phases found in the films depend primarily on the film stoichiometry. For films with a Zn/Ti ratio lower than 1, the phases found were zinc metatitanate (ZnTiO 3 ) with a hexagonal structure and titanium dioxide. In the films with a higher Zn/Ti ratio, the zinc titanate phase was ZnTiO 3 or Zn 2 TiO 4 , both possessing a cubic structure. Catalytic testing of these films in isobutane dehydrogenation showed a clear correlation between the structure and the catalytic performance. Zinc titanate phases with a cubic crystal structure were active for dehydrogenation, but the other phases were not. The most active catalyst has a Zn/Ti ratio close to 2, the stoichiometry of which corresponds to the Zn 2 TiO 4 phase. The highest selectivity to isobutene was ca. 90 mol%, both at 823 and 923 K. The isobutane conversion was 2 and 8 mol%, respectively, at these two temperatures. Compared with the catalytic performance of a zinc titanate pellet pressed from powder material, the thin film catalyst exhibited a higher activity and a remarkably better stability.

Homogeneous thin films of zinc titanate have been successfully prepared on Si(100) wafers by depositing a film of zinc and titanium oxides (ZnO-TiO2) by low-pressure metalorganic chemical vapor deposition (MOCVD), followed by an annealing treatment. The precursors used for the deposition were diethylzinc (DEZ), tetraisopropoxide titanium (TPT), and water. By performing the deposition at temperatures between 140 and 350C, the stoichiometry of the as-deposited films could be effectively controlled over Zn/Ti ratios between 0.5 and 2.5, which cover the composition of various zinc titanate phases identified in the literature. The as-deposited ZnO-TiO2 films are amorphous, and possess a fairly smooth surface. XPS and SIMS analysis showed that the composition of these films is uniform over the wafer as well as through the films bulk. An annealing treatment of the as-deposited films at high temperature

This paper presents an overview of the different flow assurance issues associated with naphthenic acids. In field development projects a good understanding of naphthenic acid phase behavior is essential to avoid unplanned plant changes and deferment. Good data on naphthenic acid content and speciation is obtained by using a representative sample. Basic measurements (e.g. TAN) are not sufficient to obtain a detailed understanding of the flow assurance issues regarding a particular crude oil. Infrared spectroscopy and mass spectrometry, high and low resolution, are the preferred tools for analysis of crude oils. The target naphthenic acid species, e.g. ARN or fatty acids will dictate the best suited method selected for analysis. Geochemical analysis of crude oils has helped to highlight some common features which can be used for prediction purposes. For bound soap scale-forming crude oils, a large amount of complexed acids result in emulsions which are difficult to break. Chemical treatments are needed and these should be identified early in the project stages. For soap scale-forming crude oils chemical treatment requires in depth analysis of topsides equipment and impact on existing chemical portfolio. Surveillance of soap scale-forming crude oils is possible using readily available equipment. For soap emulsion-forming crude oils, paraffin precipitation adds to the stability of the emulsion formed. Chemical treatment and heat is required for best results. Use of stock tank sample properties can be used for predictions regarding the type of naphthenic acid issue to be expected for particular crude oil sets.

An extensive study has been executed to understand the mechanism of calcite scale deposition occurring in the main heat exchanger at the MPP (main production platform) facilities at SVSA. The deposit necessitated a change out of the internals of the heat exchanger, which caused production deferment and capital expenditures. The conclusion of this investigation was that the mechanism for accelerated calcite scale build-up in the HX heat exchanger is driven by the considerably high skin temperature (above 120 °C at normal heating conditions) in a high pH environment. This latter is caused by the triazine, which is part of the H2S scavenger package (used to remove H2S from some of the sour gas production), and by-products originating from the reaction of triazine (an amine) with H2S. The CaCO3 scaling tendencies and indices as calculated by scaling software (ScaleChem, StreamAnalyzer) predict the adverse impact of the high temperature and alkalinity conditions encountered in the heat exchanger. Several technical options to mitigate the effects of the scavenger were considered from an economic and operational perspective. The most effective of the options was the injection of an appropriate scale inhibitor at a suitable dosage upstream of the heat exchanger.