More operators are increasing their activity level in shale oil plays as the commodity price has stabilized. Activity has been at a fever pitch in the Permian Basin where over half of the North American land rigs drilling for oil are located. Operators realize that well performance varies both positively and negatively along reservoir quality and completion design changes as well as the drilling time of infill wells. Previous studies included investigation of the average type curve for gas wells located in core areas of various unconventional plays across the US. The Permian Basin is predominantly an oil-rich basin with multiple benches; the challenge associated with discerning which bench a well was landed in makes it difficult to compare completions. This paper seeks to generate decline trends for wells drilled in the Wolfbone and Wolfberry sequences of the Permian Basin while also examining the changes in completion evolution and parent/child relationships. A similar workflow from previous studies was also applied to generate the decline curves for wells by bench and producing year.

First, the horizontal wells were categorized based on which formation the laterals were landed in. Then, the moving window approach was used to identify the parent and child wells in each major formation. Based on this information, the production performance and completion between the parent and child wells were compared by bench and completion time.

In this paper, we investigated the change in decline rate by applying the ratio of best 1-month production (B1) and the best 12 consecutive months (B12) production rate with relation to parent and child well spacing across respective formation layers. We also examined the completion factors in combination with the child/infill well production performance to determine the production improvement and degradation causes, thereby providing a reference for child/infill well design.