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This work describes a case of a light oil field in Sub-Saharan Africa. Soon after the start up, the production wells showed a productivity index different from expectation. In particular, well test analysis showed different stabilizations between build-up and drawdown. Since the well is flowing with pressure below the bubble point, the impact of oil permeability reduction due to presence of free gas around the wellbore was considered as a possible explanation and was investigated. We applied well test analysis on synthetic data generated by numerical simulation. The analysis confirms the different stabilizations between pressure build-up and drawdown, as observed from the real field case, when the flowing bottomhole pressure is below the bubble point pressure. The different flow capacity is caused by gas saturation around the wellbore, which reduces the effective permeability to oil, hence the productivity index. Besides this, we experienced that a full field model with large grid size is not able to represent this phenomenon. Due to the grid size, the full field model shows less pressure drop than the radial sector model, hence different gas saturation calculation. We showed that in order to simulate the effect without impacting on simulation time, applying higher well skin instead of local grid refinement can be a way forward.

In the last decades, the major oil companies have moved aggressively toward challenging targets such as deep and ultra-deep water environments to increase their hydrocarbon reserves portfolio. To deal with these new targets, attractive but located in harsh environments, technology has to improve significantly as well as the attention to be paid to operate under safe conditions. Operational daily costs are generally huge, sometime in excess of 1 million US$. As a consequence, the goal is to achieve a satisfactory balance between the value of information about the reservoir to be investigated and the ability to operate in a cost-effective manner. The option of capturing real time downhole P&T data by using electric cables when testing an exploration well is considered less and less attractive due to intrinsic safety risks. This has triggered significant developments in the wireless technology in recent years. Real time data are transmitted acoustically, removing the need for wireline operations. This wireless technology proved to be very effective increasing the test efficiency, optimizing the test sequence to acquire the well/reservoir response, minimizing costs and operating in a totally safe way. A real field application on an offshore exploration gas well is presented in this paper. The test offered the opportunity to assess both benefits and limitations of the technology.

mini-DSTs are gaining more and more popularity as a possible alternative to conventional well testing especially where there are major environmental and economical constraints. The increased offshore exploration activity, which often implies highly risky and huge operational costs, makes the conventional well testing less attractive in favor of other technologies that can provide some of the key dynamic information about the well-reservoir system through relatively quick and less expensive operations. The design phase is recognized to be one of the most critical aspects in order to guarantee an acceptable value of information in exploration scenarios where very limited data is available. The success of any mini-DST operation can be significantly compromised if two major issues are not addressed in the design phase: possibility to clearly identify the radial flow behaviour, and avoidance of noise in the pressure response due to the gauge resolution.The paper describes a new user-friendly approach for mini-DST design, which allows one to easily identify whether this technology can be successfully applied. The approach is based on the use of dimensionless and dimensional charts, which are of general validity because they can be applied to any lithological environment and for any type of hydrocarbon. Field applications proved the charts to be very powerful because they could predict the range of effectiveness of mini-DST's.

The aim of the present work is to investigate wear phenomena induced by the soot contamination in lubricated contacts, as it occurs typically in diesel engines. Blends of a base oil (mineral and synthetic) and two additives (a ZnDTP antiwear and a polybutylene succinimide dispersant) were tested on a pin-on-disk apparatus; the wear scar dimensions were then compared for uncontaminated and contaminated blends with soot-like carbonaceous paniculate. The aggregate size distribution of the solid contaminant dispersed into the blends was characterised at the same time by quasi elastic light scattering (QELS), in an attempt to point out possible correlations with the wear results. To explore how different properties of a soot-like contaminant could affect wear, different carbon blacks and a ”synthetic soot” were selected according to their morphological and surface characteristics. Results give evidence of an antagonistic interaction between the two additives under contaminated oil conditions; some influence on wear from the surface properties of the contaminants has been reported as well, while no correlations between induced wear and particulate aggregation have been found.

Fourteen years after the first observation of Caulerpa taxifolia (Valh) C. Agardh in the northwestern Mediterranean Sea, this green alga of tropical origin is now present in five countries (Spain, France, Monaco, Italy and Croatia). By the end of 1997, more than 46 km(2), at depths of between 0 and 50 m, were found to be affected by this expansion. A standardization of the cartographic procedure is proposed here. Such a standardization is necessary to compare maps produced by various organizations from different countries. For a given independent station, it is based on the definition of three levels of colonization:Level I refers to a station where one or several colonies less than 100 m apart cover a total surface area inferior to 1000 m(2):Level II refers to a station where several colonies less than 250 m apart totally cover more than 1000 m(2) with fragments and small colonies dispersed over a surface area inferior to 10 ha;Level III is attained when several large colonies are dispersed over a surface area superior to 10 ha, with a total covered surface of more than 1000 m(2), impossible to map with precision due to its size.For each of these colonization levels, descriptive parameters can be used to precisely describe the situation: covered surface area, dispersion surface (i.e. "affected" zone), estimation of very large affected zones (i.e. "concerned" zones) and the portions of the coastline along which an affected or concerned zone can be found., Quatorze années après la première observation de Caulerpa taxifolia en Méditerranée nord-occidentale, cette algue d'origine tropicale est présente dans cinq pays (Espagne, France, Monaco, Italie et Croatie). À la fin de l'année 1997, plus de 46 km2 de fonds, situés essentiellement entre 0 et 50 m de profondeur, sont concernés à divers degrés par cette invasion. Une standardisation de la représentation cartographique est proposée. L'objectif de cette normalisation est de pouvoir comparer les cartes produites par divers organismes appartenant à plusieurs pays. Elle est basée sur la définition, pour une station donnée, de trois niveaux de colonisation : ¿ - Le niveau I correspond à une station où se développent une ou plusieurs colonies (réparties à moins de 100 m les unes des autres) et couvrant au total une surface inférieure à 1000 m2 ; ¿ - Le niveau II correspond à une station où de nombreuses colonies (réparties à moins de 250 m les unes des autres) couvrent au total plus de 1000 m2 et sont dispersées dans une surface inférieure à 10 ha ; ¿ - Le niveau III correspond à une station où les colonies sont disséminées dans une zone supérieure à 10 ha et pour lesquelles la surface totale couverte (très supérieure à 1000 m2) n'est plus cartographiable avec précision. Pour chaque niveau un ensemble de paramètres descriptifs permet de préciser la situation : surface totale couverte, surface atteinte, estimation des larges surfaces atteintes (ou surface concernée), linéaire de côte devant lequel on trouve des surfaces atteintes ou concernées.

Molybdenum dithiophosphate (MoDTP) and molybdenum dithiocarbamate (MoDTC) additives are added to automotive and industry lubricants for their performance as friction modifiers and antiwear agents. In recent years an increasing attention has being paid to these additives, because they can improve energy saving. However their effectiveness may be strongly affected by synergistic or antagonistic effects of additive packages.

Problem statement: Wireline formation testing (also named Mini-DSTs) are gaining more and more popularity as a possible alternative to co nventional well testing especially where there are major environmental and economical constraints. The increased offshore exploration activity, which often implies highly risky and huge operational cos ts, makes the conventional well testing less attractive in favor of other technologies that can provide some of the key dynamic information about the well-reservoir system through relatively quick and less expensive operations. The design phase is recognized to be one of the most critical aspects i n order to guarantee an acceptable value of information in exploration scenarios where very lim ited data is available. The success of any mini- DST operation can be significantly compromised if t wo major issues are not addressed in the design phase: possibility to clearly identify the radial f low behavior and avoidance of noise in the pressure response due to the gauge resolution. Approach: The study consisted in the development of a new too l for mini-DST design to easily identify whether this technology can be successfully applied. The tool comprises dimensionless and dimensional charts, which are of general validity because they can be applied to any lithological environment and for any type of hydrocarbon. Results: Field applications proved the reliability of the charts: First of all the test durations were optimized to collect interp retable bottomhole pressures and to obtain valid reservoir characterizations. Besides, a cost saving effectiveness was achieved avoiding the acquisition of useless extra-data affected by noise due to gauge resolution. Conclusion/Recommendations: The use of the charts is strongly suggested at the early stage of decision making for new exploration/ appraisal operations; they are a user-friendly tool for assessing the feasibility of a mini-DST test. A dditionally, the charts are more versatile with res pect to available commercial software in managing uncertainties of the major input parameters.