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In a wellbore, loss of zonal isolation can be caused by the mechanical failure of the cement or by the generation of a microannulus. However, the behavior of the sealant is driven by the specific boundary conditions like the rock properties. Large-scale laboratory testing of the cement sheath in an annular geometry and in a confined situation was performed to simulate various well conditions and to evaluate the behavior of several sealants under simulated downhole stress conditions. The failure modes of the cement sheath were determined as a function of the cement mechanical properties, loading parameters, and boundary conditions. The results were used to validate an analytical model that predicts cement sheath failure. Introduction Interzonal communication in a wellbore may lead to loss of reserves, contamination of zones, production of unwanted fluids, or safety and environmental issues. Remedial solutions exist to repair the problems, but for technical or economical reasons, the well may be shut in or abandoned. To improve the lifetime of the well, the cement sheath must be chemically and mechanically durable. Sealants resistant to aggressive formation fluids are designed when required. In the same way, sealants should be designed to withstand the stresses experienced during production and well operations - e.g., casing pressure tests, stimulation treatments, or temperature changes during production cycles-throughout the well life. To achieve this, a better understanding of the mechanical behavior of different sealants under downhole conditions is required to design fit-for-purpose materials.1,2 Several papers have been written on the subject. According to Thiercelin et al.,3 changes in downhole conditions can cause mechanical damage to the cemented annulus (mechanical failure or creation of microannuli) that may lead to a loss of zonal isolation. The key conclusion of that paper was that instead of considering the strength of the sealant as the main property, one should rather look at the complete mechanical system formed by the steel casing, the cemented annulus, and the formation. Indeed, increase of pressure and/or temperature in the wellbore firstly expands the inner steel casing, which instantly imposes this deformation on the neighboring cement sheath. As a consequence, imposed displacements rather than imposed stresses are applied to the cement inner diameter (ID). At a greater time scale (the lifetime of the well), the cement sheath must withstand multiple displacement cycles. Several authors have proposed numerical models4,5 to simulate the sealant mechanical behavior and predict initiation of failures according to known mechanical properties of the complete system (steel, cement, and rock). A large-scale laboratory test for sealants in an annular geometry has been developed. Changes in the well conditions resulting in either the contraction or the expansion of the inner casing can be simulated. Furthermore, the confining role of the formation or outer casing can be evaluated. Such an experiment allows the evaluation of the sealant mechanical response under wellbore conditions. Indeed, the nature of stresses generated in the annulus (tensile and/or compressive) is similar to those the sealant must withstand in a real wellbore. The loading scenario simulated in the full-scale annular sealing test is close to reality. Several cement systems exhibiting different mechanical behaviors have been tested, and the experimental results have been compared with the predictions of a numerical model. Laboratory experimentation The experiments are designed to compare different cement formulations at room conditions in a large-scale annular geometry and determine the effect of cement mechanical properties and boundary conditions (rock stiffness) on cement cracking and permeability to air. Imposed deformations can be applied on the cement ID to simulate changes in wellbore conditions caused by variations of temperature and/or pressure. Equipment The equipment developed for the study is shown in Figs. 1 and 2. There are two main components.

Summary Loss of zonal isolation in a wellbore can be caused by mechanical failure of the cement or by development of a microannulus. However, behavior of the sealant is driven by specific boundary conditions such as rock properties. Large-scale laboratory testing of the cement sheath in an annular geometry and a confined situation was performed to simulate various downhole stress conditions and evaluate the behavior of several sealants. Failure modes of the cement sheath were determined as a function of cement mechanical properties, loading parameters, and boundary conditions. Results were used to validate an analytical model that predicts cement-sheath failure. Introduction Interzonal communication in a wellbore may lead to loss of reserves, contamination of zones, production of unwanted fluids, or safety and environmental issues. Remedial solutions exist to repair the problems, but for technical or economic reasons, the well may be shut in or abandoned. To maximize well life, the cement sheath must be chemically and mechanically durable. Sealants resistant to aggressive formation fluids should also be designed to withstand stresses exerted during production and well operations, such as casing-pressure tests, stimulation treatments, or temperature changes during production cycles. To achieve this design goal, a better understanding of the mechanical behavior of different sealants under downhole conditions is required.1,2 According to Thiercelin et al.,3 changes in downhole conditions can cause mechanical damage (e.g., mechanical failure or creation of microannuli) to the cemented annulus, which may lead to loss of zonal isolation. Thiercelin et al.'s paper3 concludes that the complete mechanical system formed by the steel casing, cemented annulus, and formation should be considered, rather than sealant strength alone. Increase of pressure and temperature in the wellbore first expands the inner steel casing, which instantly imposes this deformation on the surrounding cement sheath. This applies imposed displacements, rather than imposed stresses, to the cement inner diameter (ID). Over the lifetime of the well, the cement sheath must withstand multiple displacement cycles. Several authors4,5have proposed numerical models to simulate sealant mechanical behavior and predict initiation of failures according to known mechanical properties of the complete system (i.e., steel, cement, and rock). A large-scale laboratory test for sealants in an annular geometry has been developed. This test simulates changes in well conditions that cause contraction or expansion of the inner casing. It can also evaluate the confining role of the formation or outer casing. Such an experiment enables the evaluation of sealant mechanical responses under wellbore conditions. The tensile and compressive stresses generated in the annulus are similar to those the sealant must withstand in a real wellbore. Loading simulated in the full-scale annular sealing test is close to real field conditions. Several cement systems exhibiting different mechanical behaviors have been tested, and the experimental results have been compared with predictions of a numerical model.

OBJECTIVES Our goal was to analyse the influence of preoperative aortic regurgitation (AR) on the necessity of cusp repair during valve-sparing reimplantation (VSR). We focused on patients with tricuspid aortic valves (TAV) and evaluated the impact of AR and cusp repair on long-term outcomes. METHODS From March 1998 to December 2018, a total of 512 consecutive patients underwent VSR at our institution; of these, 303 had a TAV. The mean age was 53 ± 15 years, and the median follow-up was 6.12 years. The rate and type of cusp repair were analysed based on preoperative AR. Time-to-event analysis was performed, as well as risk of death, reoperation and AR recurrence. RESULTS Cusp repair was necessary in 168 (55.4%) patients; the rate rose significantly as AR grade increased (P < 0.001). In-hospital mortality was 1% (n = 3). At 5 and 10 years, overall survival was 92 ± 2% and 75 ± 5%, respectively. Freedom from valve reoperation was 95 ± 2% and 90 ± 3%. Freedom from AR >2+ and AR >1+ at 10 years was 88 ± 4% and 70.4 ± 4.6%, respectively. Independent predictors of death included age, New York Heart Association functional class and type-A aortic dissection. Predictors of AR greater than mild included previous cardiac surgery and severe preoperative AR. CONCLUSION In patients with TAV receiving VSR, the necessity of cusp repair increased with the degree of preoperative AR. Preoperative AR and cusp repair do not impact long-term survival and aortic valve reoperation, but severe preoperative AR and multiple cusp repair increase the risk of recurrent moderate-to-severe AR. Overall, cusp repair seems to attenuate the negative impact of preoperative AR for at least 1 decade in a majority of patients.

Background: We report the clinical and echocardiographic results of our experience in robotic mitral valve repair over a 7-year period. The outcomes of the earliest and the latest patients will be compared.

Background During the ongoing COVID-19 pandemic, healthcare workers are facing shortage in personal protective equipment, especially adequate respirators. Alternative do-it-yourself respirators (ADR) emerge, without any proof of protection. Objective Verify seal potential of two ADR compared to a common FFP2 respirator. Design Quality assessment pilot study. Setting Tertiary Care Hospital. Participants Ten anaesthesiology residents. Interventions Participants performed quantitative face-fit tests (QNFT) with three respirators to evaluate seal. A common FFP2 respirator was used as baseline (control group). ADR tested in this study are an Anaesthesia Face Mask (AFM) and a full-face Modified Snorkelling Mask (MSM) with a 3D-printed connector, both in conjunction with a breathing system filter. Main outcome measures Non-inferior seal performance of ADR over FFP2, assessed by calculated QNFT based on measured individual fit factors, as defined by the Occupational Safety and Health Administration. Results For each respirator a total of 90 individual fit factor measurements were taken. Within the control group, seal failed in 37 (41%) measurements but only in 10 (11%) within the AFM group and in 6 (7%) within the MSM group (P < 0.001 respectively). However, when calculating the final, mean QNFT results, no statistically significant difference was found between respirators. Successful QNFT were determined for 5 out of 10 participants in the control group, for 8 in the AFM group (P = 0.25) and for 7 in the MSM group (P = 0.69). Conclusion Both ADR do have the potential to provide non inferior seal compared to a common FFP2 respirator. While AFM respirators are easily assembled, snorkelling masks must undergo significant but feasible modifications. Our results suggest that those ADR masks might be further investigated as they seem to be viable alternatives for situations when certified respirators are not available.