Drilling performance is usually benchmarked by analysing the time spent on well construction and the degree to which planned times and budgets are achieved. Learn-curve analysis can provide indicators of relative improvement over a campaign, and position on the learning curve can provide a measure of process maturity.

However, the variability of the data makes it difficult to obtain a good fit to the model and assess maturity. The principal cause of the discrepancy between planned and actual times is trouble. Trouble is accounted for in planning by a multiplicative contingency factor. This implies that trouble time is dependent on well or well-section length.

Based on a standardized analysis of drilling performance for a wide range of wells we find that this assumption is not valid and that trouble time is not significantly correlated with well or well-section length. However, we do find that the probability of trouble is significantly correlated with length, and that a probability plot of trouble time for a group of wells or well sections provides a robust measure of drilling process maturity.

We present results of applying this analysis to a variety of well types and propose some metrics for assessing drilling process maturity.