Laboratory-Scale Studies on Chemical Reactions Between Fracturing Fluid and Shale Core From the Marcellus Shale Energy and Environmental Laboratory (MSEEL) Site

Abstract

Injection of fracturing fluids into shales during hydraulic stimulation can result in various chemical reactions involving the injected fluid and host shale rock. Differences in chemical composition between the injected fluids and fractured rock can result in mineral precipitation along shale fractures and within the shale matrix, potentially affecting long-term gas recovery from the shale. Our prior research showed that mineral precipitation and dissolution occur along freshly-generated fractures, and within the shale matrix, during core flood experiments in which laboratory-fractured Marcellus Shale was exposed to simulated hydraulic fracturing fluids. Many of the mineral precipitation reactions were hypothesized to occur due to the inability for antiscaling compounds in the fracturing fluids to control mineral precipitation at elevated temperature and pressure. In some locations along the fracture, proppant was cemented to shale surfaces through secondary mineral precipitates. The present study focuses on core flood experiments using fresh core and site hydraulic fracturing fluid from the Marcellus Shale Energy and Environmental Laboratory site (MSEEL; Morgantown, WV) at reservoir pressure and temperature conditions. The objectives of this study are to evaluate the reproducibility of the earlier experiments using fresh core, and to identify causes for any observed differences with the prior outcrop-based experiments.

An Integrated Multiscale Modeling Framework for Unconventional Stimulation and Production (Final Report)

“…At the reservoir-scale, the framework is built upon integration of two existing high-performance simulators for reservoir-scale behavior: the GEOS code for hydromechanical evolution during stimulation (Settgast et al, 2017) and the TOUGH+ code for multi-phase flow and chemical evolution during production (Moridis & Pruess, 2014). At the micro-scale, we deploy sophisticated imaging and testing methods (Voltolini and Ajo-Franklin, 2020;Hakala et al, 2017;Li et al, 2019), combined with reactive transport simulations (Tournassat & Steefel, 2019;Steefel & Tournassat, 2021) to develop a fundamental understanding of the mechanical and chemical processes within the propped fractures and across the fracture-rock interfaces. Constitutive upscaling relationships built upon this fundamental understanding are then incorporated in the reservoir-scale simulators.…”

“…These include, for example, the permeability evolution of propped fractures in different types of shales over a range of stress conditions (Voltolini et al, 2017) or the fracture aperture changes and proppant embedment in shales exposed to different types of fracturing fluids (Vankeuren et al, 2017;Moore et al, 2018). Researchers also studied dissolution and precipitation reactions across the fracture-matrix interface (Hakala et al, 2017;Marcon et al, 2017;Harrison et al, 2017;Jew et al, 2017a, Jew et al, 2017bJew et al, 2018; and demonstrated that properties of the shale matrix and fractures can be affected by mineral precipitation arising from the injected fluids (fracture to rock) and chemical alterations to the shale itself (matrix to fracture). In ultra-low permeability rocks, especially those with > 20 wt.% clay, geochemical reactions can reduce overall permeability by more than 40% (Allali et al, 2018).…”

A New Modeling Framework for Multi-Scale Simulation of Hydraulic Fracturing and Production from Unconventional Reservoirs

“…At the reservoirscale, the framework is built upon integration of two existing high-performance simulators for reservoir-scale behavior: the GEOS code for hydromechanical evolution during stimulation [4] and the TOUGH+ code for multi-phase flow and chemical evolution during production [5]. At the micro-scale, we deploy sophisticated imaging and testing methods (e.g., [6][7][8]), combined with reactive transport simulations [9,10], to develop a fundamental understanding of the mechanical and chemical processes within the propped fractures and across the fracture-rock interfaces. Constitutive upscaling relationships built upon this fundamental understanding are then incorporated in the reservoir-scale simulators.…”

“…These include, for example, the permeability evolution of propped fractures in different types of shales over a range of stress conditions [13] or the fracture aperture changes and proppant embedment in shales exposed to different types of fracturing fluids [14,15]. Researchers also studied dissolution and precipitation reactions across the fracture-matrix interface [7,[16][17][18][19][20][21][22] and demonstrated that properties of the shale matrix and fractures can be affected by both mineral precipitation arising from the injected fluids (fracture to rock) and chemical alterations to the shale itself (matrix to fracture). In ultra-low permeability rocks, especially those with > 20 wt.% clay, geochemical reactions can reduce overall permeability by more than 40% [23].…”

Multi-Scale Microfluidics for Transport in Shale Fabric

“…Connected pathways are engineered in these low-permeability rocks by injecting high-pressure acidic fluid, often followed by a 'shut in' or accumulation period, and finally commercial recovery of hydrocarbons [17]. The high-pressure fluid physically breaks the rock, while the acidity chemically interacts with the fracture surfaces, resulting in the evolution of these flow channels and their apertures [18][19][20] over time. The result is a transient growth and connection of the natural fracture fabric, leading to complex fracture geometries [21][22][23] through which the hydrocarbons are transported to the wellbore and produced on the surface.…”