Blowouts represent one of the most severe threats associated with exploration and exploitation of petroleum resources, involving the risk of losing human lives, environmental and economic values. In particular, today's focus on protection of the environment and the ambitions of the industry to operate safely in environmentally sensitive areas generates a need for improved cross disciplinary tools and work processes within blowout risk management. This paper will present a methodology aiming to form the foundation for a new standard for blowout risk assessment. Both details of the analysis method and its contributions to improving the risk management work process will be addressed. The new methodology combines knowledge from different technical disciplines by merging hydraulic flow modelling and different blowout duration models in a Monte Carlo simulation framework, and differs from traditional blowout evaluation methods both in terms of how to collect input data to the analysis and the way the final result is presented and communicated. This methodology introduces a common working platform for HSE engineers and the other disciplines involved in well planning, thus improving cross communication between different disciplines. The paper will present the building blocks of the methodology and illustrate its application on a case from the Norwegian Continental Shelf. Introduction In the petroleum industry, a blowout is among the events that may potentially cause catastrophic consequences to human life and health, the environment and economic values. In this paper we will focus on management of environmental risk, and in particular on the analysis of blowout flow rate and duration for use in environmental risk analysis. Several risk management activities are carried out in order to deal with blowout risk. Environmental risk management is important in general, particularly in environmentally sensitive areas, where the potential consequences are high and contingency planning for major accidents requires extra attention. This is an increasingly important theme, as the petroleum industry is moving to new and challenging areas and the public awareness around these issues is high. The calculation of blowout rate and duration is a part of the contingency planning for all operators on the Norwegian Continental Shelf. Well prepared planning includes reflecting a blowout incident in the well design, in ensuring proper communication and understanding within the operating company and in being able to communicate the results from the blowout contingency planning to third parties. The operating companies perform risk analyses addressing potential damages on environmental resources which can result from drilling, completion, operation and maintenance of wells. The evaluation of possible blowout scenarios resulting in discharges of oil or condensate is a central theme in the analyses. The calculated risk to exposed environmental resources is compared to criteria for acceptable risk and enters into the dimensioning for oil spill preparedness. Today's practice in E&P companies varies with respect to level of detail, treatment of uncertainty, terminology, documentation and traceability of the blowout analysis. Due to lack of international and national standards relevant for environmental risk analysis, the Norwegian Oil Industry Association (OLF) has developed recommendations based on a reference methodology in order to standardize terminology, procedure and documentation of blowout calculations. BlowFlow, a software tool and methodology developed by IRIS, meets the recommendations stated in the OLF report [1] by establishing a common methodology and workflow that can help standardizing terminology, methodology, documentation and communication related to the calculation of blowout discharges, thus improving communication within and between companies and to give decision makers stronger confidence with respect to blowout related issues.

The drilling of wells for which there is a small pressure margin is often challenging with respect to well control issues. A kick, which occurs if the wellbore pressure drops below the pore pressure, is one of the major risks being dealt with in the planning phase of the well. A kick can occur due to several factors, such as human errors, equipment failures or a wrong pore pressure prognosis. Since the ultimate consequence of a kick may be a blowout, it is essential to be able to assess and reduce the probability of a kick occurring. In order to be able to quantitatively assess well control risks, a tool and methodology called KickRisk has been developed for supporting technical and operational decisions in the well planning phase. The methodology is based on a probabilistic framework which takes into account a variety of factors that may cause a kick, and the calculations are executed by means of Monte Carlo simulation. The methodology allows the analyst to:Quantify the probability of kick and fracturingSystematize all information relevant to the occurrence of a kickPinpoint critical factorsEvaluate alternative solutions on e.g. well design and operational proceduresQuantify the effect of risk reducing measures This paper will present the overall probabilistic approach and the composition of the KickRisk model. Further, it will be shown how the KickRisk methodology can be incorporated into a risk management workflow. The practical application of the methodology will be explained through a case study. Introduction The oil and gas industry is taking on increasingly challenging drilling operations; drilling in severely depleted, mature reservoirs, HPHT drilling, deep water drilling and ultra deep wells being some examples. In any drilling operation, proper well control is essential. Loss of well control may ultimately lead to a blowout, which represents one of the most severe threats associated with exploration and exploitation of petroleum resources, involving the risk of human lives, environmental and economic values. The more challenging the operation, the more efforts should be spent in the planning phase on assessing the risks related to loss of well control. When analyzing new and unproven drilling technology, or drilling in challenging environments, statistical or experience data are rarely available. Thus, in order to assess risks related to such operations, a well specific approach is often the only option. A well specific approach can be undertaken by employing a probabilistic risk assessment approach, which provides a body of practical techniques that can help engineers and risk managers to predict and manage risks in a variety of complex engineered systems. The KickRisk methodology employs this approach. Proper well control is typically ensured by using two independent barriers, named primary and secondary barrier, see for example [1]. The primary barrier is the mud or fluid column and the secondary barrier is the blowout preventer (BOP) along with all elements in the well that makes it a hydrocarbon container. The KickRisk methodology addresses the potential loss of both these barriers, however, this paper only addresses the loss of the primary barrier, i.e. a kick occurring. Avoiding the occurrence of kicks is important in several respects; firstly, since the blowout probability is proportional to the kick probability, efforts made to reduce the kick probability directly reduces the blowout probability, secondly, kick incidents can be costly in terms of added well construction time and potential damages in the well and finally it can hurt an operating company's reputation.

Along with technical preparations before drilling a well, cost estimation is one of the central activities leading up to an AFE (Authorization for Expenditure) approval. Traditionally, a single well cost estimate has been provided. However, in recent years a probabilistic well cost estimate, or at least an understanding of the potential well cost range, is required as a part of the internal procedures of the E&P companies. In order to introduce and strengthen the application of probabilistic well cost estimation, a tool and methodology has been developed for use in Eni E&P drilling departments. The challenges encountered during the development of the methodology were to lower the threshold for drilling engineers to perform probabilistic well cost estimation and to systematize the corresponding workflow such that:assessment of risks and uncertainties are made simple and transparentalternative well designs can be compared in terms of cost uncertaintiesthe major risk drivers are understoodthe results can easily be communicated to other parts of the organization This paper aims at strengthening the argumentation for using probabilistic well cost estimation, give a brief overview of the underlying mathematics, present the full workflow as performed by a drilling engineer using the tool and give several examples of how the tool can be applied and communicated in a decision making setting. A case study is presented in order to illuminate the above points. Introduction The petroleum industry faces growing pressure to reduce well construction costs. Well construction cost estimates have to a large extent been based on historical data, which mask serious risks in the project under consideration. The well construction cost estimation has been reflecting the uncertainty and the range of values that the well construction cost can take to a limited extent by only providing 10th and 90th percentile values in addition to the most probable value. Redesigning a well in progress can result in a poor well plan because of late notice and insufficient time. The total time taken in well construction operations is subject to considerable uncertainty and risk factors due to limited knowledge concerning the geologic characteristics of the formation, technical difficulties and unexpected behaviour of human operators. This time represents 70 to 80% of the final well construction cost due to high costs of the daily rent of the drilling rig, see [1]. Well construction duration is therefore an important issue regarding budget planning. This paper introduces a method for estimation of well construction cost and duration based on expert judgments in combination with experience data. The results provide the spread in the estimated values together with important values like for example the mean and the 10th, 50th and 90th percentiles. If several alternative solutions for the well construction are available, results from the well construction cost estimation can easily be compared. This paper first presents traditional and probabilistic well cost estimation, and pinpoints advantages and disadvantages by the two methods. A mathematical description of probabilistic well cost estimation is provided. Then the work flow is described. Use of the method in a well cost risk management setting is presented, including examples of application. This is followed by a discussion on how the results should be communicated and used for decision making. An example case is then described in order to demonstrate the use of the probabilistic well cost estimation method in well construction planning. Finally a conclusive summary of the paper is given.

When planning oil and gas wells, the cost and duration uncertainty, related to the well construction process, could be a big concern.Traditionally, Drilling Engineers, in different geographical areas, have utilized different estimation methods with a consequent difficulty of communication. This tool could represent a common platform on the well construction cost and duration estimation.In recent years probabilistic well cost estimates have become a requirement as part of the internal procedures of the E&P Companies, e.g. when applying for an Authorization for Expenditure (AFE) approval.This paper describes the tool and methodology which have been developed upon request by Eni E&P to introduce and strengthen the application of probabilistic well construction cost and duration estimation within the drilling department. The tool offers decision support for well and operation planning and has the potential to make the cost and duration uncertainty analysis an integrated activity of the well planning process.The software is characterized by a user friendly interface and is tailored to Drilling Engineers' needs, to easily and effectively perform the probabilistic risk analysis and to systematize the corresponding workflow.It also facilitates both internal and external communication, since it has the potential to be used as a standard tool.In conclusion, the developed tool allows Drilling Engineers to:• perform a quantitative risk analysis;• calculate risked cost and duration;• identify operations which mostly affect drilling uncertainties;• evaluate and select alternative technical solutions;• prepare prevention and mitigation plans for the reduction of both duration and cost.

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