Production degradation due to parent-child effects is one of the biggest concerns for operators in the most active shale play developments such as the Permian and SCOOP-STACK plays in the US (McClure et al., 2022; Lindsay et al., 2018; Cozby & Sharma, 2022). Various papers have described the positive, negative, and neutral consequences to both parent and child wells after child well stimulation and completions. The purpose of this work is to provide a workflow for quantifying the impact of parent-child depletion to estimate future child well performance based on available data. The set of equations and relationships presented were derived using a dataset of Permian wells and applied to a Vaca Muerta data set and are presented in a way that anyone can replicate an analysis on an existing data set.
We introduce a Parent Depletion Index (PDI) calculated by using the parent cumulative oil at onstream date of child well, overlap of parent and child lateral sections horizontally, horizontal distance between parent and child wells, and vertical distance between parent and child wells, for all parent wells within a defined radius from a given child well. This work outlines best practices to determine an appropriate radius. The workflow introduces alpha and beta factors that can be linearly regressed and used to calculate a Parent-child Factor (PCF). The resulting workflow allows for empirically-derived estimates of future child well performance based on well spacing and offset parent cumulative production and yields scaling factors that can be applied to type curve and decline curve analysis-based (DCA) production forecasts.
There are multiple sources that discuss parent-child performance-related impacts across different shale basins and some papers have shown hard data that illustrates the impact of parent depletion during child fracturing that they in turn modeled:
• Brinkley et al. show an example from the Eagle Ford where they used fiber optics, wellbore pressure modeling, downhole pressure gauges, time lapse geochemistry and iterative production interference tests that demonstrate the impact of depletion, and outline mitigations techniques (2023).
• Raterman et al. used fiber optics among other diagnostics demonstrate child fracturing can be impacted by wells 1700 ft (520 m) away, though they emphasize a difference between "interference and competitive drainage" (2020).
• Ugueto et al. show clear evidence in the Permian of preferential child fracture growth toward depleted parent zones as measured by microseismic and fiber optics (2022).
• Trevor et al., 2020 uses Chow Pressure Group (CPG) modeling to define interference/depletion impact with time (2020).