Semi‐empirical notch sensitivity factors q have been used for a long time to quantify notch effects in fatigue design. Recently, this old concept has been mechanically modelled using sound stress analysis techniques, which properly consider the notch tip stress gradient influence on the fatigue behaviour of mechanically short cracks. This mechanical model properly calculates q values from the basic fatigue properties of the material, its fatigue limit and crack propagation threshold, considering all the characteristics of the notch geometry and of the loading, without the need for any adjustable parameter. This model's predictions have been validated by proper tests, and a criterion to accept tolerable short cracks has been proposed based on it. In this work, this criterion is extended to model notch sensitivity effects in environmentally assisted cracking conditions.

j m a t e r r e s t e c h n o l . 2 0 1 3;2(3):288-295 w w w . j m r t . c o m . b r Environmentally assisted cracking a b s t r a c t Empirical notch sensitivity factors q have been used for a long time to account for notch effects in fatigue design. This old concept has been recently modeled using sound mechanical principles to properly quantify the influence of the stress gradient around the notch tip on the fatigue behavior of mechanically short cracks. This model can be used to calculate q values from the basic fatigue resistances of the material, its fatigue limit and its crack propagation threshold, considering all the characteristics of the notch geometry and of the loading. This model predictions have been validated by proper tests, and based on this experimental evidence a criterion to accept tolerable short cracks has been proposed.In this work the mechanical principles that support this criterion are extended to account for notch effects in environmentally assisted cracking problems.

The removal of the filter-cake formed during the drilling operation is essential for a successful cementing job. Nowadays the use of synthetic base fluids brings the necessity of proceeding new evaluations of the efficiency of the washes in removing the filter-cake and to guarantee the wettability inversion of the formation from oil to waterwet. It is presented here a new method of evaluating the filter-cake removal efficiency performed by different washes. This method uses a natural core with a perforation, where a filter-cake is formed by circulating a drilling fluid. The wash is circulated through this perforation and the filter-cake removal efficiency is measured precisely by Computer Tomography Scanning. This method enables the filter-cake removal visualization during the wash circulation through the formation. From the data obtained from the X-Ray Tomography it is possible to select the most appropriate wash for a given drilling fluid, as well as to predict the necessary contact time between the wash and the formation to achieve an appropriate filter-cake removal. Introduction To achieve successful cementations, it is important to get an optimum removal of the drilling fluid and the filter-cake out of the annulus. Beirute et al1 have presented tests perfomed in a large-scale equipment consisting of a 20 ft hole using a man-made formation. The results obtained proved the importance of a proper condioning of the drilling fluid prior the cementing operation. Smith et al2 have made tests simulating drilling fluid circulation, conditioning and cementing using a large-scale equipment. Ravi et al3 have presented the concept of erodability of mud layers by using also large-scale equipment. The evaluation of the filter-cake removal in the lab has been historically performed by the following techniques:Visual observation or mass difference evaluation of pieces of tile initially immersed in drilling fluid and then immersed in the chemical wash under study. Movement would be provided by a magnetic stirring system.Visual observation of the removal, by a chemical wash, of drilling fluid film previously formed in the internal wall of a becker. Stirring would be provided by the use of a rotational viscometer at a fixed speed (normally 100 RPM). At this point, a series of advantages or disadvantages of both methods could be listed and discussed. But it is clear that both of them are far from simulating well conditions prior to the cementing operation. The main goal of this paper is to propose a more realistic method to represent the dynamic phenomena of the filter-cake removal process. This method includes the displacement of fluids through an orifice made in a natural core and the filter-cake removal monitoring by a computer tomography (CT). The complete approach for selecting a chemical wash includes, besides filter-cake removal, other important issues which are not addressed in the article, such as: its capacity to invert formation wettability and the compatibility among all the fluids involved in the cementing process (wash, drilling fluid, spacers and cement slurries). Experimental Apparatus It will be discussed about the two equipment used in the evaluation of the filter-cake removal efficiency: the rock-fluid interaction flow loop and the tomography system.

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The present paper describes the establishment and implementation of the technology governance in the well area at Petrobras, which includes R&D, qualification and homologation projects. Corporate standards delineated the technology governance to assure uniformity and impersonality. It comprises two main processes: (i) establishment of technical specifications; (ii) technology evaluation. The former includes the elaboration/review of technical specifications focused on functional, quality and reliability aspects and clearly defined normative requirements. The latter process begins with the presentation of the technology by the potential suppliers and evaluation of interest by the project areas. Subsequently, in accordance with the readiness level assigned to the technology, it may be allocated as a R&D, qualification or homologat ion project, addressing to the appropriate treatment and assuring celerity for the necessary analysis. To operationalize the whole process, Petrobras created a department in well area responsible for structuring and leading processes related to the admission of new technologies to the company, linked with the already well established R&D process. Deliberative forums have been held with managers of all the technical areas involved allowing collegial decision. Prioritized projects have been conducted by multidisciplinary working groups, including representatives from project and operation team, contract department, and also well experts. All technology process deliveries are reported by means of standard documents and are recorded in corporate system ensuring traceability and technical memory preservation. Nowadays, all the processes are well established and running for over 2 years with good feedback from stakeholders. It is worth mentioning the improvements in communication flow between and within departments and teams, better definition of roles and responsibilities reducing interface issues and easy availability of information that may be accessed for all parties involved with the projects. Additionally, there is a continuous improvement for system solutions assuring input, maintain, control and consult the whole information shared throughout the process. The method adopted based on technology readiness level for new equipment/material/service assessment is aligned to good practices from other segments, such as aerospace industry. Moreover, technical specification focused on functional, quality and reliability requirements and system solutions for quick information availability complies with IOGP recommendations, ISO standards and with an increasingly restrictive regulation scenario especially after the lessons learned post-Macondo.