Paper Number
MM16 

Session
Microrheology and Microfluidics

Title
High-pressure linear viscoelasticity measurements of polymer solutions and gels

Presentation Date and Time
October 10, 2017 (Tuesday) 4:35

Track / Room
Track 6 / Aspen

Authors (Click on name to view author profile)

1. Dennis, Kimberly A. (University of Delaware)
2. Gao, Yan (Schlumberger)
3. Phatak, Alhad (Schlumberger)
4. Furst, Eric M. (Univ. of Delaware, Dept. of Chemical & Biomolecular Engineering)

Author and Affiliation Lines (in printed abstract book)
Kimberly A. Dennis¹, Yan Gao², Alhad Phatak², and Eric M. Furst^1
1University of Delaware, Newark, DE 19716; ²Schlumberger, Sugar Land, TX 77478

Speaker / Presenter 
Dennis, Kimberly A.

Text of Abstract
Oilfield fluids are used to help transport and suspend solids, reduce friction pressure and prevent fluid loss. Key to these fluid performance metrics is the fluid rheology. Depending upon the composition and flow condition, the fluid can behave as a purely viscous or viscoelastic fluid. By choosing the right composition, the flow properties can be optimized for a specific function. Mechanical rheometers are used extensively for rheological measurements of fluids. However, mechanical rheometers cannot always provide accurate measurements for all the systems. Misinterpretation of rheological data may provide underestimated or exaggerated fluid features, which may in turn lead to the failure of a specific task. In addition, many of the fluids are heterogeneous, thereof change in macrorheology does not reflect the microstructure evolution of the material. Further, high-pressure measurements can be challenging for mechanical rheometers.

To address these shortcomings, we developed a passive microrheology experiment to measure the linear viscoelasticity of complex fluids at high pressures. The apparatus incorporates a sealed steel sample chamber with dual sapphire windows into a simple diffusing-wave spectroscopy (light-scattering) setup and is capable of both transmission and backscattering geometries. The measured light intensity correlation arising from the Brownian motion of polystyrene probe particles dispersed in the sample is interpreted using the generalized Stokes-Einstein relation to determine the material creep compliance. We validate this high-pressure microrheology technique with ethanol and poly(ethylene oxide) aqueous solutions and extend the measurement to stimulation fluids containing a crosslinked guar biopolymer. We investigate the effect of crosslinker density on rheological properties at frequencies up to 1 MHz and pressures of 200 MPa, expanding the accessible range of experimental conditions beyond those of existing rheological measurement techniques.