Case Study: Optimizing Hydraulic Fracturing Performance in Northeastern United States Fractured Shale Formations

Abstract

Abstract The primary purpose of stimulating fractured shale formations is to extend the drainage radius by creating a long fracture sand pack that connects natural fractures and increases flow channels to the wellbore. However, most of the fracturing pad fluid leaks off into natural fractures resulting in shorter effective fracture lengths and a significant damage zone surrounding the fracture. This is due in part to inadequate fluid loss control properties of the injected fluid and high capillary forces that retain fluid in the formation. Surfactants are used to lower high capillary forces and help well cleanup of the injected fluids. However, many of these additives adsorb rapidly within the first few inches of the shale formation, reducing their effectiveness and resulting in phase trapping of the injected fluid. In this work, laboratory data is presented for various fracturing fluids with different surface activity pumped into the Rhinestreet Shale. Recent fracture treatments have been successful utilizing a slick water treatment consisting of water and dry polyacrylamide polymer with and without surfactants. Commonly used surfactants as well as a microemulsion system are evaluated in this study. Laboratory data is presented illustrating how a microemulsion accelerates post fracturing fluid cleanup in tight shale cores. Addition of microemulsion to the fracturing fluid also results in lowering pressure to displace injected fluids from low permeability core samples and proppant packs. When microemulsion is incorporated at 2 gpt within the fracturing fluid; the relative permeability to gas is increased substantially while water saturation is decreased. This alteration of the fracturing fluid effectively lowers the capillary pressure and capillary end effect associated with fractures in low permeability reservoirs by as much as 50%, thus mitigating phase trapping and therefore permitting an increased flow area to the fracture, hence longer effective fracture lengths.