Colonization process of marine growth increasingly arouses the interest of the oil industry because engineering design or reassessment of platforms requires forecasting of biological fouling specific to the area where they are located. Numerous publications related to marine growth on installations of North Sea, Gulf of Mexico, or oil sites in other parts of the world tried to answer the need to supply more quantitative data on biological fouling. Unfortunately, there is a lack of qualitative and quantitative published data in the Gulf of Guinea, where biological fouling has a significant impact on cost of structural inspection and maintenance because of the importance of colonization due to favorable environmental parameters (warmer temperature of seawater, intense action of the waves generating a mixing of the nutritive elements, strong light, etc.). This paper is dedicated to bridge that gap and describe ecosystem dynamics of marine growth in the Gulf of Guinea. We describe patterns of development for dominant types of biofouling in the region. Analyses of evolution and related kinetics parameters are carried out to give main trends of colonization process. Predictive models of marine growth development and their statistical parameters are proposed for reassessment and engineering design.

The Congo Basin and the adjacent equatorial eastern Atlantic are among the most active regions of the world in terms of intense deep moist convection, leading to frequent lightning and severe squalls. Studying the dynamics and climatology of this convection is difficult due to a very sparse operational network of ground-based observations. Here, a detailed analysis of recently available high temporal resolution meteorological observations from three oil platforms off the coast of Angola spanning the three wet seasons from 2006/07 to 2008/09 is presented. The annual cycle of squall days as identified from wind data closely follows that of convective available potential energy (CAPE) and therefore mirrors the cycle of wet and dry seasons. The diurnal cycle of squall occurrence varies from station to station, most likely related to local features such as coastlines and orography, which control the initiation of storms. An attempt to classify squalls based on the time evolution of the station meteorology and satellite imagery suggests that microbursts account for at least one-third of the strong gusts, while mesoscale squall lines appear to be quite rare. On a daily basis the probability of squall occurrence increases with increasing values of CAPE, downdraft CAPE, and 925-700-hPa wind shear, and decreases for high convective inhibition, all calculated from vertical profiles of temperature and humidity at the nearest grid point in the NCEP-NCAR and ECMWF reanalysis datasets. Both the climatological results and the stability indices can be used for local forecasting to avoid squalls impacting on operations on the offshore platforms.

Squalls are one of the main issues for the design of West Africa floating units mooring systems. At the present time and due to the lack of more relevant information and models, squalls are represented by on site time series of time varying wind speed and relative heading. The first FPSO units were designed on the basis of a reduced Squall database. Nowadays, the number of squall records has been significantly increased and a response based analysis can be carried out. The present paper is focused on the Gulf of Guinea environment. The area has been divided into two zones: North (Nigeria…) and South (Congo, Angola…). This approach enabled us to deal with 90 Squall events for North zone and 115 Squall events for South zone. Two different mooring systems, with quite different natural periods, have been investigated in order to cover the range of already installed spread moored FPSO’s. For every Squall of the database, time domain and modal simulations have been carried out in order to obtain the maximum values of the axial tension in mooring lines and of the offset of a standard spread moored unit. Then a statistical procedure is applied a) to estimate 100-year return period values for these parameters and b) to assess overall trends besides the differences between results from both zones and both mooring systems. A comparative study has also been carried out to relate the 100-year return period extrapolations with the values derived from classical design procedures in order to evaluate the potential design margins for extreme responses. Finally, areas needing further investigation are identified.

Reassessment of existing offshore structures needs rational aid tools to update new information (metocean data, new regulations, ...). This paper focuses on marine growth management on Jacket offshore structures. After years of exploitation, marine growth thickness reaches up to the initial beam diameter. Inspection and cleaning are actions to be optimized, keeping in mind that safety must be preserved according to cost reduction. The paper first presents the building of an exhaustive data base in view to use the whole available information. An illustration is given for structures placed in Gulf of Guinea: main species, colonization process as well as modeling of thickness increasing are discussed. A modeling of hydrodynamic coefficient is then suggested according to kinematics field and physical response surface.

Monitoring of currents is of high importance for Oil and Gas industry, especially when it comes to design, offload and support to operations. Various monitoring techniques, existing nowadays, with each having their own pros and cons, are briefly discussed in the paper. The objective of study was to compare current data acquired by Unmanned Surface Vehicle (USV), used offshore South America East Coast to support seismic acquisition survey in 2013, to the ones measured by conventional oceanographic mooring (COM) deployed in the same area. Consistency of these datasets was investigated. Efficiency, flexibility and applicability of "static" (mooring) versus "dynamic"(USV) solution for current monitoring applications are discussed. Data analysis started with plotting time series of current speed at selected depth levels. The quick comparison made it possible to discuss data comparability and current speed and direction patterns. The analysis was followed by establishing scatter diagrams, directional distributions and Quantiles-Quantiles plots, which in turn made it possible to conclude on overall data representation, consistency and agreement. USV are relatively new in Oil and Gas industry. Its advantageous feature of being a lowcost, autonomous and quite flexible solution makes them extremely promising for applications in the industry. Positive results from a comprehensive statistical comparison of the datasets showed that it is possible to accurately collect the current data by means of USV, meaning that USV can be considered alternative to conventional oceanographic mooring. Some recommendations on suitable use of each of the techniques are provided following the conclutions from the study.