When a child well is hydraulically fractured near the depleted reservoir volume surrounding a previously produced parent well, it is economically efficient to deliver proppant to the formation volume and fractures not reached by the parent well. A fracture length, which is the distance fluid travels from the child well to the depleted region, is calculated as a function of fracture stage. From identified trends in fracture length, fracture length for future stages can be predicted. Based on predicted fracture length, the slurry or treatment volume to cause well interference can be estimated. Proppant concentration or fracturing stage design can be adjusted so that the well interference volume is larger than the treatment volume and proppant is efficiently delivered to the child well fractures.