Fracture-Fluid Chemistry Optimization to Improve Hydrocarbon Recovery for Shale and Tight Assets

Abstract

The active development of unconventional shale and tight reservoirs worldwide has helped unlock vast quantities of hydrocarbons in recent years. Hydraulic fracturing operations in horizontal wells is the most common method applied to unconventional reservoirs to unlock hydrocarbon resources by undergoing multiple fracturing stages. A common mixture of friction reducer, scale inhibitor, and other situational additives along with a carrier fluid, (brackish or recycled produced water) make up the completion or frac fluid. Often, the frac fluid is a colloidal suspension, as noted by the larger particle size distribution within the fluid. When exposed to reservoir conditions (elevated temperature, high formation brine salinity, high divalent ion concentration), frac fluids can destabilize due to the presence of polyacrylamide acting as a flocculant. Such behavior causes phase-separation and precipitation resulting in formation damage. Another scenario is the rapid production rate decline seen in hydraulically fractured horizontal wells. Typically, their production rates rapidly decline until stabilizing at a low terminal rate. Overcoming these trends to improve recovery is a major challenge. Fracture Fluid Chemistry Optimization (FFCO) technology development focuses on increasing recovery by designing and optimizing fracturing fluids for stimulation of shale formations. This stimulation fluid maintains clean fractures and penetrates deeper into the fracture network, mobilizing more hydrocarbons by altering rock wettability and lowering interfacial tension (IFT). The surfactants also alter the relative permeability to a more favorable state in the propped fractures. This work describes a workflow to optimize treatment fluids for injection into shale and tight rock reservoirs. The workflow incorporates rock and fluid property measurements and compatibility assessments between rock, reservoir fluids and frac fluids at the laboratory scale.