Production decline analysis in the Eagle Ford

The Eagle Ford shale went from no significant oil production to overtaking the Wolfberry play as the fastest producing oil field in Texas in less than five years. This is thanks to advances in hydraulic fracturing and horizontal drilling technology which has lead to a shale oil boom in southern Texas. We want to understand the resource potential of the Eagle Ford, so we perform decline analysis on each well in the field. With this decline analysis we offer predictions for the ultimate recovery of 10,285 oil and gas wells. In order to perform these predictions, we fit historical production to recovery factor curves, with two fitting parameters describing time to boundary dominated flow (BDF) and resource in place. The recovery factor curves are numerically calculated to describe production of shale wells at different reservoir pressures using real fluid properties. The Eagle Ford has a large variety of fluid types, from heavy oil to dry gas, so we create a class of recovery curves for each fluid type. We build recovery factor curves using a pseudopressure formulation of one dimensional flow for gas and condensate wells. For oil wells, we use a new regular pressure formulation based on slightly compressible liquids. The analysis finds that 5671 wells have entered BDF, with an average time to BDF of 14.2 months. For wells that have not yet entered BDF, we assign a time of interfracture interference comensurate with imminent interference. This is a conservative estimate, but the most realistic estimate we can supply. We predict that the 9,664 wells will produce 5.83 Tcf of gas and 1.39 Bstb of oil over their lifetimes.