Probabilistic Modeling for Well-Construction Performance Management

Abstract

As the search for hydrocarbons necessitates the exploration of everdeeper waters and remote locations, operators who wish to plan well construction in the most credible and cost-effective way, and who demand the most efficient execution, are increasingly employing probabilistic methods. One of the most compelling features of probabilistics is that, as opposed to the traditional deterministic "best guess" scenario, plans are based on finite uncertainty. Uncertainty will always remain a feature of operations involving people and equipment in a changing environment. Excellent planning incorporates uncertainty and allows better preparation at all stages of well execution. Model BuildingProbabilistic methods are a powerful tool to make useful and credible models of well-construction activity. Full implementation of a probabilistic approach will enhance the ability of a team to manage performance.Planned and Unplanned Events. A probabilistic well-construction model comprises not only the desired sequence of planned events but also should include unplanned events. The process may start with a group "brainstorming" session to identify the nature of all events that could occur during operations. The brainstorming sessions can be productive and inclusive if the focus is maintained on the steps required to progress the well. Following an unplanned event, for example, the group would be asked what additional steps or mitigating steps should follow to return to the planned sequence. The brainstorming approach generates a good qualitative model from which a quantitative model will follow.Visualization. The definition of a planned sequence of events and the discipline of visualizing unplanned events are key distinguishing features of the probabilistic process. Unplanned events are defined as anything that you do not intend to do but are required to do anyway. Unplanned events are often characterized as "nonproductive time." The probabilistic model can be used to visualize all of the events that could have an impact on the detailed program. People often refer erroneously to a sequence of unplanned events as a "worst-case scenario." It is a fact that having described a series of unplanned events, one can imagine an escalation into an even worse scenario. The threshold for inclusion of an unplanned event in a probabilistic model is to determine: (a) Can we exert some control over the frequency of the event occurring? (b) Can we exercise any control over the sequence of events that follow an unplanned event? (c) Is there anything in the drilling program that we will change as a result of modeling these events? For example, a tsunami or helicopter crash would not be included in a well-construction model. Lost circulation, stuck pipe, and well control would all be candidates for inclusion.Anticipation of Events. One of the most disruptive features of well construction is the occurrence of unanticipated events. The traditional deterministic method of writing down a proscribed sequence virtually guarantees that the detailed plan will n...

Risk measurement of international oil and gas projects based on the Value at Risk method

“…applied a probabilistic model to analyze the impacts of the key terms in a royalty contract on the NPV of an international OG projects. Besides, other scholars applied a probabilistic model to production prediction (such as Rivera et al (2007)), to well construction (such as McIntosh (2004) and Adams et al (2010)) and so on.…”