Wax deposition is one of the most challenging flow assurance issues in oil production processes. The related problems span from reservoirs to refineries, but their consequences can be particularly challenging when the affected area is difficult to reach, such as producing wells. The wax deposition in the areas adjoining the bore, the bore face, the tubing string and the pump is the result of the cooling effect, which occurs when the oil flows from the high-pressure reservoir into the wellbore to the surface. During the depressurization the oil expands, and the heat is drawn from the oil. The temperature loss induces crystallization of the wax and the subsequent plugging of the well. In this case, wax deposition leads to the decrease of well flow rates and eventually causes total blockage. This paper sums up the main technologies applied to prevent or remediate the wax deposition formed inside the wells. A comprehensive review was presented, and the main advantages and disadvantages of these techniques were highlighted. For instance, the mechanical removal is still a widely used technique for solving wax problems inside wells, despite being a costly procedure; heating is another frequent used technique, but it can cause formation damage; bacterial treatments still require further studies on site conditions; changing the operational conditions may be undesirable due to other management field circumstances; coating and insulating materials generally are not fully efficient, being required to implement complementary techniques; cold flow was only tested in pipelines and it was not applicable to wells; finally WIT, electric and magnetic field or oscillatory motion are practical applications that have not been fully proven yet. Keywords Wax deposition inside wells • Wax prevention techniques and wax removal techniques

No abstract

Water and crude oil emulsions can be produced during oilfield operations. Since most oilfields are in the secondary or tertiary recovery stages, the amount of produced water is not negligible. Furthermore, enhanced oil recovery makes use of surfactants injection (chemical substances that lower the surface tension of the liquid) and polymer flooding (polymers are large molecules, composed of repeating blocks bounded together, which are injected to decrease the water–oil mobility ratio), leading to increased emulsion problems. Knowledge of fluid petrochemical properties and behavior is fundamental for designing the production system, transport infrastructures, and refinery layout. Depending on the fluid composition, the flow rate, and the PVT conditions, different physical behaviors and flow patterns will occur. Even though significant effort has been carried out to take a broader view of liquid–liquid models, there is a wide range of correlations to consider with different crude oil compositions and diverse field conditions. In this work, a critical review was carried out to assess the main principles that affect an emulsion, how the flow patterns are influenced by the water fraction, which equations can be used to estimate the main physical properties, and last what are the methods or techniques for identifying or characterizing an emulsion. As a result, a strong background in this matter is offered, and future research directions are synthesized.

No abstract

Throughout the last two decades, seismic design standards evolved to ever more comprehensive and detailed prescriptions, stressing out the need for design methods that deal with earthquake effects not as actions, but as a design philosophy. The Eurocode 8 adoption as national law throughout the European Union countries and informally in many parts of Africa, Asia and Latin America is the pretext for the current study. It aims to provide some guidance to the seismic design of steel structures as well as to the Eurocode 8 implementation by the designers.Some lines on the preliminary design of structural systems were written based on several real cases of structures designed taking into account the seismic action. Such a content is, usually, relevant in any design guide, given its value in enhancing the design technical and economical content. However, it is now of utter significance at the current context as an essential tool to facilitate the safety checking of several code requirements.Some of the Eurocode 8 prescriptions are then decoded, explained and justified based on the supportive bibliography. The information is subsequently ordered as a design guide, where some procedures are proposed to cope with the code interrelated prescriptions and one structural solution is proposed in order to overcome a design challenge while complying with the code.One last but not less relevant addressed issue is the fact that some Eurocode 8 prescriptions may be reviewed, in the eyes of a designer, given its practical outcome. Such issues are identified, explained and some slight code adjustments are suggested.