Probabilistic analysis of risk and mitigation of deepwater well blowouts and oil spills

The development of robust risk assessment procedures for offshore oil and gas operations is a major element for the assessment of the potential feedback between planned activities and the environment. We illustrate a methodological and computational framework conducive to (1) a quantitative risk analysis of deepwater well barrier failures and subsequent hydrocarbon release to the environment and (2) the analysis of the value of the deployment of conventional and/or innovative mitigation measures. Our methodological framework is grounded on historical records and combines the use of Dynamic Event Trees and Decision Trees from which we estimate probability of occurrence and impact of post-blowout events. Each sequence of response actions, which are undertaken immediately after the event or in the subsequent days, is considered within the context of appropriately structured event paths. This approach is conducive to an estimate of the expected value of key decisions and underlying technologies, with an emphasis on their potential to reduce the oil spill volume, which can critically impact the environment. Our study yields an original comparative analysis of diverse intervention strategies, and forms a basis to guiding future efforts towards the development and deployment of technologies and operating procedures yielding maximum benefit in terms of safety of operations and environmental protection

A novel fully plastic caliper pig for low-risk pipeline inspection - Design, Characterization and Field Test

Pipe in-line inspection by "intelligent" pigs is a fundamental oil and gas industry practice but still considered as an exceptional operation. In fact, the instrumented pigs addressing such a purpose are expensive and delicate tools with non-negligible operating risks, thus making their deployment rather infrequent (typically, once every several years). In eni we have started a number of R&D initiatives targeted to making pipeline inspection easier and more frequent by significantly reducing the operating risk faced when deploying inspection pigs. In this context, we present a new, low-cost and low-risk plastic pig with inspection capabilities analogous to those of a multichannel caliper pig (i.e. able to detect, locate and size inner diameter changes and deformations) together with additional features allowing to detect internal roughness changes (e.g. due to corrosion) and perform some pH/salinity determinations, also useful for corrosion assessment purposes. One implementation of the new tool makes use of a foam pig "body", providing the required push with a good capability to negotiate restrictions, equipped with specialized sensors and modules for acquisition and storage. Another implementation, targeted to gas lines and called "skeleton caliper pig", deploys the light plastic system without any foam pig carrier, pushed by the gas velocity alone, and is suitable to prevent the massive displacement of condensates from gas lines. The paper describes the design, construction and field testing of this new low-risk caliper pig, together with some comparisons with the information gathered adopting a conventional tool

Experimental study of aqueous foam generation and transport in a horizontal pipe for deliquification purposes

This work presents and analyses the results of experimental activities aimed at a preliminary characterization of foamy flows for pipeline dewatering, in order to assess whether the addition of surfactants may effectively reduce the liquid holdup in horizontal pipelines. Static tests were run to compare the foam cycle (generation and decay) for three commercial surfactants and to choose the most suitable one. Dynamic tests with the selected product were performed in a 20 m long, 60 mm i.d. Plexiglas® pipe, where a 0.3% wt. solution of surfactant in tap water was pumped after mixing with an air flow at nearly atmospheric pressure and temperature. Superficial velocities ranged between 0.03 m/s and 0.05 m/s for water and between 1.5 m/s and 11.5 m/s for air, which would determine stratified/stratified wavy flows in the case of pure water-air flow, i.e. the benchmark case. Due to the presence of the surfactant, foam formed in the mixing section, which implied a significant change in the flow patterns that were photographically recorded and classified into three main types: plug, stratified wavy and stratified with foam entrainment, as far as the air superficial velocity was increased at constant water superficial velocity. The associated pressure drop, linearly distributed along the pipeline, resulted greater than the benchmark value in all the operating conditions, with a dramatic increase (even more than 100%) for plug flows. On the other hand, the percentage relative difference was found to lower with increasing the air superficial velocity, apart for stratified wavy flows where it seemed to keep constant at about 3.3%. Finally, a theoretical model for stratified flows was used to relate the pressure drop to the void fraction in order to get at least an approximate indication of the liquid load reduction due to the surfactant addition, which ranged between 6% and 39%

Positive end-expiratory pressure (PEEP) level to prevent expiratory flow limitation during cardiac surgery: Study protocol for a randomized clinical trial (EFLcore study)

Background: Lung dysfunction commonly occurs after cardiopulmonary bypass (CPB). Randomized evidence suggests that the presence of expiratory flow limitation (EFL) in major abdominal surgery is associated with postoperative pulmonary complications. Appropriate lung recruitment and a correctly set positive end-expiratory pressure (PEEP) level may prevent EFL. According to the available data in the literature, an adequate ventilation strategy during cardiac surgery is not provided. The aim of this study is to assess whether a mechanical ventilation strategy based on optimal lung recruitment with a best PEEP before and after CPB and with a continuous positive airway pressure (CPAP) during CPB would reduce the incidence of respiratory complications after cardiac surgery. Methods/design: This will be a single-center, single-blind, parallel-group, randomized controlled trial. Using a 2-by-2 factorial design, high-risk adult patients undergoing elective cardiac surgery will be randomly assigned to receive either a best PEEP (calculated with a PEEP test) or zero PEEP before and after CPB and CPAP (equal to the best PEEP) or no ventilation (patient disconnected from the circuit) during CPB. The primary endpoint will be a composite endpoint of the incidence of EFL after the weaning from CPB and postoperative pulmonary complications. Discussion: This study will help to establish a correct ventilatory strategy before, after, and during CPB. The main purpose is to establish if a ventilation based on a simple and feasible respiratory test may preserve lung function in cardiac surgery. Trial registration: ClinicalTrials.gov, ID: NCT02633423. Registered on 6 December 2017

Associations Between Expiratory Flow Limitation and Postoperative Pulmonary Complications in Patients Undergoing Cardiac Surgery

Objectives: To determine whether driving pressure and expiratory flow limitation are associated with the development of postoperative pulmonary complications (PPCs) in cardiac surgery patients.Design: Prospective cohort study.Setting: University Hospital San Raffaele, Milan, Italy.Participants: Patients undergoing elective cardiac surgery.Measurements and Main Results: The primary endpoint was the occurrence of a predefined composite of PPCs. The authors determined the association among PPCs and intraoperative ventilation parameters, mechanical power and energy load, and occurrence of expiratory flow limitation (EFL) assessed with the positive end-expiratory pressure test. Two hundred patients were enrolled, of whom 78 (39%) developed one or more PPCs. Patients with PPCs, compared with those without PPCs, had similar driving pressure (mean difference [MD] -0.1 [95% confidence interval (CI), -1.0 to 0.7] cmH(2)O, p = 0.561), mechanical power (MD 0.5 [95% CI, -0.3 to 1.1] J/m, p = 0.364), and total energy load (MD 95 [95% CI, -78 to 263] J, p = 0.293), but they had a higher incidence of EFL (51% v 38%, p = 0.005). Only EFL was associated independently with the development of PPCs (odds ratio 2.46 [95% CI, 1.28-4.80], p = 0.007).Conclusions: PPCs occurred frequently in this patient population undergoing cardiac surgery. PPCs were associated independently with the presence of EFL but not with driving pressure, total energy load, or mechanical power. (C) 2021 Elsevier Inc. All rights reserved