Approach With Simple Tools Enables Well-Spacing Optimization for Unconventionals

Abstract

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 208882, “No Reservoir Model? No Problem. Unconventional Well Spacing Optimization With Simple Tools,” by Patrick Miller, SPE, Darcy Redpath, SPE, and Keane Dauncey, SPE, Petronas. The paper has not been peer reviewed. _ Optimizing economics for unconventional resource development is a delicate balance. To search for the optimal pad design, operators often invest in integrated technical work flows with multiwell fracture modeling and reservoir simulation. Although useful, these work flows are not practical for every asset in a portfolio because they simply take too long. As an alternative approach, the complete paper builds on existing tools in the literature to quantify the effect of changing well spacing on well productivity for a given completion design, using a new, simple, intuitive empirical equation. Methodology: Understanding Well-Performance Changes With Well Spacing The four key drivers of pad economics for unconventional plays are commodity prices, reservoir deliverability, completion design, and well spacing. Completion design and well spacing must be considered together because the drainage area of an unconventional well is driven by the size of the fracture stimulation. Finding the global maximum of the optimization criteria with traditional technical work flows is intensive in terms of human resources and time. Furthermore, these traditional work flows are still only estimates of well performance under different conditions. This section of the complete paper provides a set of visual references for what is happening in the subsurface when well spacing is changed for a given fracture stimulation design and then discusses how this can be represented mathematically. The goal of the authors, in discussing currently used approaches, is to set the background for an alternative, easy-to-understand approach to define shared reservoir factor (SRQ) as a function of well density in a way that creates the expected concave down shape initially but which transitions to a linear relationship and trends toward a relative estimated ultimate recovery (EUR) of 0% at 0 well spacing. The methodology of this approach is provided mathematically in this section of the complete paper.