PNNL Successes with Novel Stimulation Solutions

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Laboratory-scale stimulation system with acoustic emission sensing for real-time monitoring of fracking processes featuring:
A & E-ISCO pumps that apply and control confining pressure around rock sample F and deliver racking fluids inside a rock sample void; B & D-manometers that monitor confining pressure and fracking fluid pressure; C-acoustic emissions sensors for real-time monitoring of fracture creating/propagation; F-EGS-type rock sample; and G-controllers that maintain constant temperature up to 400°C. Source: Dr. Carlos Fernandez, PNNL.

Laboratory-scale stimulation system with acoustic emission sensing for real-time monitoring of fracking processes featuring: A & E-ISCO pumps that apply and control confining pressure around rock sample F and deliver racking fluids inside a rock sample void; B & D-manometers that monitor confining pressure and fracking fluid pressure; C-acoustic emissions sensors for real-time monitoring of fracture creating/propagation; F-EGS-type rock sample; and G-controllers that maintain constant temperature up to 400°C. Source: Dr. Carlos Fernandez, PNNL.

2015 marked a string of significant recognitions and accomplishments for Dr. Carlos Fernandez and his team from Pacific Northwest National Laboratory (PNNL) for their GTO-funded research in developing stimuli-responsive fracturing fluid with engineered, reversible physical properties. This included multiple peer-reviewed publications in high-impact scientific journals, a patent application, numerous presentations and well-received press releases, interest in collaboration from a number of private companies, and most notably, receiving the prestigious 2015 Global Award from The Institution of Chemical Engineers (iChemE). 

PNNL researchers have extensively characterized the properties of a novel stimulation solution they developed, subjecting it to a wide range of pressure and temperature settings for measuring volume expansion, viscosity, shear rate, and chemical evolution. The solution, comprised of a polymer that can expand up to 2.5x its original volume, is triggered by a pH drop associated with the presence of CO2. Based on lab testing performed on samples from Coso field (CA) and Newberry Volcano (OR) this volume expansion introduces significant stresses on the reservoir rock, without inducing extremely high pressures.  This represents a potentially important difference over traditional hydraulic fracturing operations that rely primarily on exceeding formation fracture pressures for stimulation. For one particular experiment, results show that the stimulation material was capable of inducing fractures in rock with a force nearly 70% below traditional stimulation techniques. An advantage that will continue to be explored is the potential of the polymer to change and reverse its physical properties, where an associated pH decrease would return the polymer to its original state and size, allowing for the stimulation materials to be collected for potential recycling.

In 2016, the project team plans to fully identify the mechanisms lending to their successful induced fractures via polymer expansion. Additionally, the team seeks to understand how far the fractures can continue to propagate beyond the initial reacted fluid and volume expansion. Answering such questions are critical for understanding how PNNL’s research could help optimize reservoir creation in enhanced geothermal systems.