Experimental Investigation on the Influence of Operation and Formation Parameters on Fracturing Fluid Flowback

Abstract

Advancements in hydraulic fracturing stimulation, and lateral drilling lead to a commercial-scale exploitation of unconventional tight reservoirs. When the production of shale oil and gas took off, concerns addressing the safety of these operations rose to an alarming rate. Most of these concerns are related to the high pressures involved in hydraulic fracturing and the contamination caused by the fracturing fluid that might leak into nearby freshwater aquifers. A low fracturing fluid recovery can be an indication of environmental and health hazards. Despite the research conducted in the unconventional shale sector, there is no clear answer to why the percentage of fracturing fluid recovery is highly variable from one operation to the other, even for the same geological formations. Insights from the literature suggest that the flowback performance is affected by several parameters such as shut-in pressure, proppant pack conductivity, fracture network complexity, shut-in time, and having high permeability regions connected to the induced network. In this research, we designed and assembled an in-house experimental setup that mimics an actual hydraulic fracturing operation at a laboratory scale. The samples were designed using an innovative approach leveraging 3D printing, molding, and assembly techniques to investigate the impact of the aforementioned parameters on flowback percentages. Results indicate that increasing the shut-in pressure can have two opposing effects on the flowback percentage depending on the permeability of the matrix and that increasing the shut-in time will decrease the flowback percentage. Also, the flowback percentage drops for more complex fracture networks, and smaller proppant particle sizes. Moreover, having a hydraulic connection between the fracture network and a high permeability region will decrease the flowback percentage due to fluid losses. The work done in this research can be used as a reference to qualitatively predict the flowback performance of hydraulic fracturing operations.