Abstract
Using large-scale hydraulic fracturing experiments on tight shale outcrops we identified three dominant regions controlling stage production: (1) the connector between the wellbore and the fracture system, (2) the near-wellbore fracture and (3) the far-wellbore fracture network. The particular nature of these regions may change depending on the play, the reservoir fabric, its relation to the in-situ stress, and the distribution of rock properties. However, these regions are always well differentiated. Understanding the role of each of these components, to hydrocarbon production, is fundamental to identify the dominant sources of loss of fracture conductivity and accelerated production decline. The conditions promoting the loss of fracture conductivity, fracture face permeability and surface area in contact with the reservoir vary significantly along the length of the hydraulic fracture. By separating the induced fractured area into three characteristic regions of reservoir contact, we isolate the dominant drivers of loss of production per region, and obtain the best compromise for sustained stage productivity. We used large-scale hydraulic fracturing experiments to develop and validate the concept. These were integrated with scaled-down measurements of fracture conductivity, proppant embedment and the effect of rock-fluid sensitivity. We find that the critical conditions for productivity for the wellbore-connector depends on mechanical stability considerations and are independent of reservoir quality. The critical conditions for productivity from the near-wellbore fracture are solids retention in the proppant pack, and reduction of fracture face permeability due to proppant embedment. The critical conditions for productivity from the far-wellbore fracture are loss of surface area and retention of fracture conductivity. Results provide a framework for improving fracture design for improved long-term productivity. This is achieved by understanding the conflicting requirements between three regions of flow within the fracture and selecting the optimal compromise between these.
