A data-driven approach to identify net-pay cutoffs

The concepts of net reservoir (good-quality reservoir rock) and net pay (good-quality hydrocarbon-bearing reservoir rock) are intrinsically related. A knowledge of net pay is important for the volumetric estimation of hydrocarbon resources. Yet there is no universal definition of net pay, no general acceptance of its role in integrated reservoir studies, and no recognized method for evaluating it, and there are disparate views on how to make use of it.1 Partly for these reasons, net pay constitutes a major source of uncertainty in volumetric reserves estimates, second only to gross rock volume. This article examines the state of the industry with regard to quantifying net pay using determined formation properties and promotes an improved methodology that avoids drawbacks of traditional approaches. A specific aim is to reduce subjectivity, so that different subsurface teams can deliver more closely aligned net-pay estimates. These matters are especially important during the early stages of field life, when uncertainty in estimated petroleum resources is greatest.