Sensitivity analysis of the main variables affecting the EUR response under parent-child effect, using a comprehensive simulation workflow in the core of Vaca Muerta

The topic of this paper is related to the study of what is known in the industry as the “parent-child” effect. This is accomplished by using a coupled hydraulic fracture and reservoir simulator to perform a sensitivity analysis of the impact on the results of the EUR of the child well, based on a conceptual static model for the core of the Vaca Muerta, considering two landing zones, different spacing between wells, degree of depletion of the parent well, the addition of a second child well and the use of an improved completion design for the child well. The objective is to investigate, through sensitivity analysis, the scenarios with the greatest impact on the EUR of the child well and to measure the magnitude or influence of each of them. Once the dynamic simulation model is calibrated, the first step is to locate and stimulate a fictitious child well in the vicinity of its parent well and perform various sensitivity analyses by varying one variable while holding the other variables constant. We considered two key variables: the well spacing (200m, 300m, 400m and 600m) and the time lag between the start of production of the child well and its parent well, with depletion intervals ranging from 0 to 5 years. A second sensitivity analysis is performed by adding two child wells, 300m and 600m from the parent well, to be stimulated simultaneously using the previous time intervals. Finally, using the 300m well spacing scenario, an improved completion design for the child well was proposed and compared to the actual completion. The result of analyzing a single child well and varying the well spacing over time intervals was, as expected, the improvement for the impairment of the child well EUR at greater distances from the depletion area, with no effect observed for the 600m spacing situation. For the case of two child wells analysis, the EUR for the outer child well at 600m showed some degree of effect (different from the previous 600m case) and for the inner child well at 300m the EUR response was similar to the single child well at 300m spacing. Finally, changing the completion design drivers (specifically volumes per cluster) of the child well showed an improvement in child well EUR reduction over the current design. The significance of this project is to establish a workflow, or methodology, for evaluating the influence of the parent-child effect on EUR using numerical simulations that can be applied and adapted to any unconventional formation characteristics and input variables (well spacing, completion design, etc.), allowing an informed strategy definition for field development and optimized EUR. This working methodology is based on a fracture simulation software that integrates 3D reservoir model, hydraulic fracturing, and production simulations, using a single package designed to analyze the entire life cycle of a well, from fracturing to long-term production, making it suitable for the objectives of this project.