An Integrated Methodology for the Evaluation of the Safety and Environmental Consequences of a Blow-out

Abstract

Increasingly stringent HS&E requirements inevitably leads to an improvement in the predictive risk analysis tools used to estimate the HS&E consequences of a major accident. One potentially major accident, associated with the exploration and exploitation of hydrocarbon fields, is a blow-out e.g. an uncontrolled release of formation fluid from the reservoir. In the event of a blow-out it is essential to implement the blow-out contingency plan as quickly as possible to minimise the potential damage, particularly for onshore wells where the oil and gas is dispersed into the atmosphere and over the land. To improve the evaluation of the safety and environmental consequences of a blow-out the Agip Division commissioned a multi-disciplinary R&D project. This project utilises technical and scientific support from EniTecnologie, TEA Sistemi and TEMARS companies. The main objective of this project is the development, assessment and validation of an integrated methodology for the evaluation of the safety and environmental consequences of a blow-out. The extension of the contaminated area, the gas and oil droplets concentration distribution and the oil and gas discharge flow-rates from the well are the main deliverables from the methodology. As the primary use of this methodology would be in the management of the emergency response to a blow-out it is essential to optimise the response time. Subsequently, the following predictive approaches were developed and validated against actual blow-outs:A "One Minute" estimation tool;A "Ten Minute" estimation software;A "Best Estimation" approach. To better characterise the oil droplet field from the wellhead to the environment "ad hoc" experimental work is undertaken to reproduce the real conditions associated with a blow-out. Introduction The availability of validated predictive tools for application during an accident scenario is essential. Their use should not be restricted to design activities. They generate vital information on the evolution of an accident and can be readily applied to optimise the emergency response. One potentially major accident event that is associated with the exploration and exploitation of hydrocarbon fields is an uncontrolled release of formation fluid from the reservoir e.g. a blow-out1,2. In the event of a blow-out it is essential to implement the blow-out contingency plan as quickly as possible to minimise the potential damage, particularly for onshore wells where the oil and gas is dispersed into the atmosphere and over the land and can have an impact also on people. To improve the evaluation of the safety and environmental consequences of a blow-out the Agip Division commissioned a multi-disciplinary R&D project. This project utilises technical and scientific support from Eni Technologie, TEA Sistemi and TEMARS companies. Due to the wide range of knowledge and expertise required by this project (e.g. safety, reservoir, drilling, completion and well fluid dynamic, discharge phenomena and atmospheric dispersion) it proved necessary to "integrate" the various disciplines to ensure good quality project deliverables. The key features of the project are described in the following sections.