The SPE has split the former "Management & Information" technical discipline into two new technical discplines:
- Data Science & Engineering Analytics
The SPE has split the former "Management & Information" technical discipline into two new technical discplines:
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Lake Kivu is unique among East African Rift lakes with high concentrations of dissolved carbon dioxide (CO2) in that it also contains methane (CH4). The dissolved gases constitute a hazard because a vertical disruption of the water could cause gas-laden water to be displaced to shallower depths with lower pressures, allowing the gas to bubble out of solution and triggering a gas eruption. A floating gas-extraction facility has been constructed to extract gas-laden water, separate the methane and some of the CO2, and reinject the degassed water, thus increasing the safety of the lake and simultaneously providing CH4. Lake Kivu sits along the border between the Democratic Republic of the Congo (DRC) and Rwanda, in the Great Rift Valley region of Africa. The lake is approximately 89 km long, oriented in a north/south direction, and 48 km wide.
Abstract FPSOs usually require refrigeration, for removal of condensates and/or water before export of produced gas, or for treatment of gas to be used on board as fuel gas. This paper describes on-board refrigeration using a new combination of different concepts, none of which individually are new, to deliver refrigeration for FPSOs with environmental, cost, space and weight advantages. Usually, FPSO owners specify a non-flammable refrigerant, and most current applications use R-134a refrigerant. However, R-134a is a hydrofluorocarbon with high global warming potential (GWP = 1300). These high-GWP refrigerants are being phased out under the 2016 Kigali amendment to the Montreal protocol, and are already banned for new applications in many European countries. Low-GWP alternatives to R-134a include hydrocarbons such as propane (GWP = 3), ammonia (GWP = 0), hydrofluoroolefines (HFOs) and CO2 (GWP = 1). HFOs are new synthetic refrigerants with GWP generally <150, but are flammable, though less flammable than propane. CO2 was widely used as a refrigerant up to the 1930s, particularly in marine applications, but was superseded by early synthetic refrigerants such as R-12 and R-22, which were then phased out in the 1990s after discovery of ozone depletion effects. CO2 is limited in air-cooled applications at high ambient temperature conditions such as tropical climates, due to the high-pressure side of the system becoming supercritical, leading to high operating pressure and low efficiency. However, FPSOs mainly operate in deep water, and even where surface water temperature is high, say +30 deg.C as in the tropics, cold water below +20 deg.C, can be found at depths of 100-200 m, even at the equator. Use of cold seawater via deep inlet risers is already used for some other FPSO applications, and if used for cooling in CO2 refrigeration systems, the system can operate at subcritical conditions, power becomes competitive and an optimised CO2 refrigeration system can have lower power, smaller footprint and lower weight, compared to a similar optimised R-134a refrigeration system. CO2 is now a viable refrigerant for FPSOs, with environmental, cost, weight and operational advantages over R-134a. Using CO2 as above is a new combination of known concepts, none of which individually are new, to achieve a new and better refrigeration outcome specifically for FPSOs. It is not a proprietary technology of any company.
There is a great need for access to clean, safe water in many locations across the globe. DC resistivity has been demonstrated to be a viable approach to locating a good location for drilling water wells. However, lack of experience, lack of training or improper training, and no or little access to software results in the drilling of dry holes. This was the situation in Rwanda. Presentation Date: Monday, October 12, 2020 Session Start Time: 1:50 PM Presentation Time: 3:30 PM Location: 360C Presentation Type: Oral
This article, written by Special Publications Editor Adam Wilson, contains highlights of paper OTC 27247, “Plume Modeling in Lake Kivu, Rwanda, for a Gas-Extraction Facility,” by Timothy L. Morse, Nicolas F. Ponchaut, and Gary N. Bigham, Exponent, prepared for the 2016 Offshore Technology Conference, Houston, 2–5 May. The paper has not been peer reviewed. Copyright 2016 Offshore Technology Conference. Reproduced by permission. Lake Kivu is unique among East African Rift lakes with high concentrations of dissolved carbon dioxide (CO2) in that it also contains methane (CH4). The dissolved gases constitute a hazard because a vertical disruption of the water could cause gas-laden water to be displaced to shallower depths with lower pressures, allowing the gas to bubble out of solution and triggering a gas eruption. A floating gas-extraction facility has been constructed to extract gas-laden water, separate the methane and some of the CO2, and reinject the degassed water, thus increasing the safety of the lake and simultaneously providing CH4. Introduction Lake Kivu sits along the border between the Democratic Republic of the Congo (DRC) and Rwanda, in the Great Rift Valley region of Africa. The lake is approximately 89 km long, oriented in a north/ south direction, and 48 km wide. The lake is at 1460 m above sea level and has a maximum depth of approximately 485 m in its northern basin. Lake Kivu has an unusual thermal structure. At depths below approximately 80 m, the water temperature increases with depth. However, the water also contains large quantities of dissolved CO2 and salt, with concentrations that increase with depth. The density-increasing effects of CO2 and salt maintain the lake stratification despite the inverted temperature profile. The density structure of the lake is a series of relatively homogeneous mixed zones separated by density-gradient layers. The major mixed zones, beginning at the surface, are referred to as the Biozone, Intermediate Zone, Potential Resource Zone, Upper Resource Zone, and Lower Resource Zone. The Main Density Gradient separates the Potential Resource Zone from the Upper Resource Zone. The Secondary Density Gradient separates the Upper and Lower Resource Zones.
Abstract Lake Kivu, located between Rwanda and the Democratic Republic of Congo, is unique among several East African Rift lakes with high concentrations of dissolved carbon dioxide in that it also contains methane, kept in solution by the pressure of the deep water. The gas poses a potential hazard as a vertical disruption of the lake water (due to a landslide or volcanic activity) could cause gas-laden water to be displaced to shallower depths (and lower pressures), allowing the gas to bubble out of solution, triggering a gas eruption. A floating gas extraction facility has been constructed to extract gas-laden water from deep in the lake, separate the methane and some of the carbon dioxide and reinject the degassed water, thus increasing the safety of the lake and simultaneously providing methane, which will be used to generate electricity. This paper explores the computational fluid dynamics technique used to analyze the degassed water discharge plume from that facility and describes the dynamics of the plume. We used a Reynolds-Averaged Navier Stokes (RANS) model to analyze the dynamics of the degassed water plume. The density of the water, and hence the plume dynamics, is heavily affected by the water temperature and the concentration of methane, carbon dioxide, and salt. Thus the computational method tracked these quantities throughout the simulation. The background conditions in the lake (including mixed zones separated by density gradients) were also included in the model. Lake Kivu is unique in that the water temperature increases with depth. The lake remains stratified because the salt concentration also increases with depth and more than compensates for the effect of water temperature. Two main concerns were raised with the degassed water plume: (1) could there be recirculation between the water intake risers and the degassed water discharge points? (2) could the dynamics of the plume lead to an overturn of the lake and a catastrophic gas eruption? Our simulations showed that the degassed water plume ultimately stratifies within a density gradient, that recirculation does not occur, and that the discharge plume does not result in uplift or overturn of the lake for the conditions evaluated.
Abstract Lake Kivu, situated in Central Africa, contains a scientific and economic peculiarity: 63.109 m3 of methane at STP are dissolved in the deep part of this lake. The gas is held in the water by a special density stratification. The lake has recently been systematically explored during a German research expedition. With help of the results of the expedition and theoretical exploitation models the basis for development of this unique methane deposit has been created. Introduction Lake Kivu is situated in the western branch of the East African rift zone within a volcanic landscape. It contains a methane gas deposit which is of great interest from both the scientific and economic point of view. Since the gas is physically dissolved in the water, this deposit is significantly different from usual gas fields, where gas is present within the pores of rock. In Lake Kivu, however, the gas is held in the water by a stable density stratification. The lake consists of a main basin and four smaller basins. The latter ones are separated from the main basin by rises in the lake floor. They are Kabuno Bay and the basins near Bukavu, Ishungu and, Kalehe (see Fig. 1). The total water surface is ca. 2400 km2, the max. water depth 485 m and the total water volume app. 580 km3 (calc. from. top. map comp. by IRSAC in 1959). The deposit was discovered by DAMAS in 1935. Afterwards some studies were carried out in the lake by SCHMITZ and KUFFERATH 1955, DEGENS et al. 1973 and others. The quantity of the methane in Lake Kivu was estimated then to app. 45.109 m3 at STP. However, most of the data obtained, refer to the bottom of the lake, whereas the "water and gas body" of Lake Kivu was only inadequately investigated. The deposit could be used for energy production or for other industrial uses. In either case this resource is of first importance for the whole of this region in Central Africa. For this reason an investigational program for their economical development was carried out due to proposals of the states Zaire and Rwanda (see TIETZE proposals of the states Zaire and Rwanda (see TIETZE 1974, 1978, 1980). The objective was to study the feasibility for extraction of up to 109 m3 of methane at STP each year. NEW DATA At the end of 1974 and beginning of 1975, a measuring campain was carried out on Lake Kivu. Various parameters of the lake water were systematically parameters of the lake water were systematically measured in-situ at 30 locations (41 profile measurements) distributed over the entire lake (see Fig. 1). Additionally 185 water and gas samples as well as 12 sediment samples were taken from profiles, which were later analysed in the laboratory (see Fig. 2). The investigations are listed in table 1. Selected data are presented in Fig. 3–7 and some arounded values are given also in the paragraph "discussion". P. 275