Terabytes of data are being collected every day in the oilfield. Intuition suggests that the more data the better and that if a little bit of information is valuable, then a lot must be incredibly more so. And yet, is it? It is not the data itself, but the ability to put it toward some useful task which matters. One of the most concrete ways in which Big Data can be brought to bear on the everyday is through predictive analytics, the science of using facts from the past to analyze the present and predict the future. In the oil field, a simple and powerful way of making use of data and predictive analytics is for automatic surveillance by exception. By learning from the past it is possible to predict what should be happening today and compare the prediction to what is actually going on. If the two do not match then a problem has been identified and a solution found. Addressing problems early is one of the cheapest ways to boost production.