Abstract
Following partial completion of infill development in a given field, it becomes necessary to determine whether continued drilling should be pursued in the same field. The usual approaches for deciding whether to continue drilling (Swanson's mean or estimates based on lognormal methods) fail to account for variation and uncertainty. To better inform this decision, we propose implementing statistical confidence intervals (with an accompanying certainty level) for relevant features of interest. Closed form intervals and maximum likelihood based intervals for the average ultimate recovery for all wells in a field, the percent of wells in a field having ultimate recovery values above a certain benchmark value and other important features of interest are considered. Confidence intervals appropriate for both the lognormal and Weibull distribution are given. The proposed methods are illustrated with real data from 64 wells in the Devonian Richfield Dolomite of the Michigan basin (given in the appendix, Table 2). Table 1 summarizes the different confidence intervals.