The emerging Vaca Muerta Formation, located in the Neuquén Basin in Southern Argentina, is the most successful Unconventional Play outside United States. In the last few years, several blocks have initialized multi-rig development programs and operators have identified interference between existing producers and newly fractured wells during the completion. The effect known as parent-child occurs when the reservoir depletion around the parent well modifies the pore pressure and induces variations in the original stress field. As a result of this effect, the parent well could be seriously damaged, the hydraulic fracture of the child well would be less efficient and there will be an unsymmetrical recovery around the child well. The parent-child effect is usually negative and impose an additional challenge on the drilling and completion sequence of the block. This contribution is an attempt to quantify the production impact of this effect using a combination of a multi-disciplinary workflow.
Unconventional reservoirs were originally developed by small oil and gas companies with stand-alone wells spread across the different basins. Later in time when major operators started to develop these projects that requires intensive capital expenditure, the factory mode was deployed to increase operational efficiency. This development strategy requires the adjustment of well spacing and completion designs to minimize well production interference while maximizing the recovery factors and economics. Despite many optimization studies have been looking for the perfect design, the ultimate recovery of wells drilled in factory mode are negatively impacted compared to a stand-alone well. Additionally, as the development of the blocks moved forward, some new wells (child) were placed next to wells on production (parent) and operators have seen an additional negative impact commonly called parent-child. Statistical data from different US Shale Plays confirmed the negative production impact of this effect (Figure 1). This effect hits the project economics and should be considered and quantified to understand the convenience of drilling a new well next to a depleted area.