Abstract

A general assumption in unconventional development is that horizontal wells in close vertical proximity tend to interfere with each other, causing the ultimate recovery of each well to be diminished to the extent that their stimulated rock volume (SRV) overlaps. However, recent findings show that certain variations may result in beneficial acceleration of production without significantly affecting ultimate recoveries.

The purpose of this study was to model a system of two wells at different distances, and determine which frac propagation and asymmetry conditions need to be met to match this performance. Utilizing empirical data from several pairs of vertically stacked wells in the Delaware Basin, Texas, showing an inverse relationship between their vertical distance and the overall performance of each well, we used numerical simulation methods to test three theories that could potentially explain this behavior. Of these theories, only one achieved a successful history match and alignment with other field observations. This theory describes the possible mechanisms that allow for this production enhancement as opposed to severe interference in well pairs. Once a good match is obtained, this model can be used to design a fracturing sequence strategy that would help replicate these results in field applications. This model could also serve as a guide for the completion design needed to recreate the positive production effect.

The learnings from this study have the potential to add significant value in terms of return on investment (ROI) and net present value (NPV) to projects across the Permian Basin. This document provides a different perspective of well interference, showing that it could be another tool to improve reservoir production rather than a detriment of tight well spacing, as it is conventionally considered. It will be particularly useful for optimizing vertical and lateral spacing of unconventional wells in the Permian Basin.

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