An important task that petroleum engineers and geoscientists undertake is to produce decision-relevant information. Some of the most important decisions we make concern what type and what quality of information to produce. When decisions are fraught with geologic and market uncertainties, this information gathering may such forms as seismic surveys, core and well test analyses, reservoir simulations, market analyses, and price forecasts-which the industry spends billions of US dollars each year. Yet, considerably less time and resources are expended on assessing the profitability or value of this information. Why is that? This paper addresses how to make value-of-information (VOI) analysis more accessible and useful by discussing its past, present, and future. On the basis of a survey of SPE publications, we provide an overview of the use of VOI in the oil and gas industry, focusing on how the analysis was carried out and for which types of decisions VOI analysis has been performed. We highlight areas in which VOI methods have been used successfully and identify important challenges. We then identify and discuss the possible causes for the limited use of VOI methods and suggest ways to increase the use of this powerful analysis tool.

fax 01-972-952-9435. AbstractAn important task that petroleum engineers and geoscientists undertake is to produce decision-relevant information. Some of the most important decisions we make concern what type and what quality of information to produce. When decisions are fraught with geologic and market uncertainties, this information gathering may take the form of seismic surveys, core and well test analyses, reservoir simulations, market analyses, price forecasts, etc., on which the industry spends billions of dollars each year. Yet, considerably less time and resources are expended on assessing the profitability or value of this information. Why is that?This paper addresses how to make value-of-information (VOI) analysis more accessible and useful, by discussing its past, present, and future. Based on a survey of SPE publications, we provide an overview of the use of VOI in the oil and gas industry, with a focus on how the analysis was carried out and for which types of decisions VOI analysis has been performed. We highlight areas where VOI methods have been used successfully and identify important challenges.We then identify and discuss the possible causes for the limited use of VOI methods and suggest ways to increase the use of this powerful analysis tool.

Summary Underbalanced operations (UBO) are carried out to bypass drilling challenges that could be difficult to resolve by use of conventional drilling techniques. Steady-state multiphase-flow models are used to construct underbalanced-drilling operational windows. These advanced software models are deterministically formulated. It is known that some of the model input parameters, such as the multiphase-flow parameters, friction factors, and reservoir productivity, are subject to uncertainties. Failures to capture these variabilities may introduce some error in the model prediction, resulting in poor well planning and implementation. The purpose of this work is to implement probabilistic modeling of underbalanced drilling by use of a simple steady-state two-phase model. Both predefined uncertain and fixed factors serve as inputs to a pre-existing deterministic model. By applying Monte Carlo simulations, the model predicts outputs that follow a statistical distribution. A sensitivity analysis is conducted to determine the input factor that is most responsible for the uncertainty in the predicted bottomhole pressure (BHP). The results demonstrate that uncertainty modeling can improve underbalanced-drilling design and operations. A more realistic operational window is obtained, ensuring that underbalanced condition is maintained throughout the target section. With a better understanding of uncertainties and the corresponding impacts, well planners can make better decisions regarding well design criteria and safe operational conditions, and avoid huge economic consequences.

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Summary The current practice on the Norwegian Continental Shelf (NCS) when designing solutions for permanent plug and abandonment (P&A) complies with NORSOK Standard D-010 (2013). This is a prescriptive approach to P&A, as opposed to a “fit-for-purpose” risk-based approach. A risk-based approach means that any given P&A solution is expressed in terms of the leakage risk, which can be formulated in terms of the following quantities: the probability that the (permanent) barrier system will fail in a given time period, and the corresponding consequence in terms of leakage to the environment. As part of building a leakage-risk model for permanently plugged-and-abandoned wells, a simple leakage-rate calculator has been developed for quick evaluation of the leakage potential from a given (permanent) well-barrier solution. This tool is developed to serve the second aspect of the risk-based approach: the consequence in terms of leakage rate to the environment. The leakage potential from the well can then be quantitatively assessed, taking into account different leakage pathways including leakage through bulk cement, through cement cracks, and through microannuli along cement interfaces. In the paper, we will provide models to estimate leakage rate for each leakage pathway and show how to integrate them in the leakage calculator to obtain a description of leakage flow from the reservoir through failed barriers to the environment. The information and input parameters needed to achieve this will be discussed, and uncertain parameters will be treated probabilistically, thus allowing for expressing uncertainty in the leakage-rate estimate. Results from the leakage calculator will be demonstrated on a synthetic case, showing variants of a permanently plugged-and-abandoned well.